text:
Human intelligence—as usually measured by IQ tests or broader “general cognitive ability” tests—is **substantially heritable**, but not genetically fixed. The best evidence suggests that **genetic differences explain roughly 40–80% of variation in cognitive ability within studied populations**, with the estimate typically **increasing from childhood into adulthood**.

## What “heritable” means

Heritability is often misunderstood. A trait being, say, 60% heritable does **not** mean that 60% of an individual’s intelligence is “genetic.” It means that, in a particular population and environment, **about 60% of the differences between people** on that trait are statistically associated with genetic differences.

Heritability also does **not** imply immutability. Height is highly heritable, yet nutrition and disease strongly affect height. Similarly, cognitive ability is heritable, but education, health, poverty, toxins, stress, and culture can all matter.

## Approximate heritability estimates

Findings vary by age and method, but a common summary is:

- **Early childhood:** around **20–40%**
- **Middle childhood/adolescence:** around **40–60%**
- **Adulthood:** often **60–80%**

The increase with age is a well-replicated finding. One likely reason is that as people grow older, they have more freedom to select and shape environments that fit their genetically influenced tendencies—for example, reading more, choosing certain peer groups, pursuing particular interests or education paths.

## Main lines of evidence

### 1. Twin studies

Twin studies compare identical twins, who share nearly all segregating DNA, with fraternal twins, who share about half on average.

A typical finding is:

- Identical twins are much more similar in IQ than fraternal twins.
- Identical twins reared apart are still quite similar, though not identical.
- Fraternal twins and ordinary siblings are less similar.

This pattern strongly suggests genetic influence.

However, twin studies require assumptions, such as the “equal environments” assumption: that identical and fraternal twins experience equally similar environments relevant to the trait. Researchers debate the size of possible violations, but the overall evidence from many designs still supports substantial heritability.

### 2. Adoption studies

Adoption studies compare children with their biological and adoptive relatives.

Typical findings:

- In childhood, adopted children’s IQs correlate with both adoptive-family environment and biological background.
- By adulthood, correlations with biological relatives often become stronger, while resemblance to adoptive siblings or adoptive parents tends to weaken.

This suggests that family environment matters, especially early on, but genetic differences become more predictive over development.

### 3. Genome-wide studies

Modern genetic studies examine millions of DNA variants across the genome.

They show that intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with tiny effects.

Important findings:

- Common genetic variants measured by SNP arrays explain a meaningful but incomplete share of IQ variation—often called **SNP heritability**, commonly estimated around **20–30%** depending on sample and measure.
- Polygenic scores can predict some variation in educational attainment and cognitive performance, but their predictive power is still modest at the individual level.
- Genetic prediction works best in populations similar to those used to build the scores, mostly people of European ancestry in current datasets, and transfers less well across ancestries because of differences in genetic structure and research representation.

Genome-wide evidence is important because it supports twin/adoption findings using DNA directly, though it also shows that the genetic architecture is diffuse and probabilistic, not deterministic.

## Environment still matters a lot

Even if intelligence is substantially heritable, environmental influences are clearly important. Examples include:

- Quality and quantity of schooling
- Early childhood nutrition
- Prenatal environment
- Lead and other neurotoxins
- Infectious disease burden
- Sleep, stress, and mental health
- Socioeconomic deprivation
- Family language environment and cognitive stimulation

The **Flynn effect**—large IQ score increases across generations in many countries during the 20th century—also shows that population-level cognitive test performance can shift substantially over time, likely due to environmental changes such as schooling, nutrition, smaller families, cognitively demanding work, and test familiarity.

## Shared vs. non-shared environment

Behavioral genetic studies often divide environmental effects into:

- **Shared environment:** factors that make siblings similar, such as household income, neighborhood, parenting style, and school access.
- **Non-shared environment:** factors that make siblings different, such as different peer groups, illness, accidents, differential treatment, or random developmental events.

For intelligence, shared environment tends to be more important in childhood and less apparent in adulthood in many affluent populations. Non-shared environment and measurement error account for much of the remaining variation.

## Heritability depends on context

Heritability is not a universal constant. It can change depending on:

- Age
- Social inequality
- Educational access
- Nutrition
- Range of environments in the population
- Measurement quality
- Historical period

In a society where everyone has similar nutrition and schooling, a larger share of remaining differences may be genetic. In a society with severe deprivation or unequal schooling, environmental differences may explain more.

## What the evidence does *not* show

The evidence does **not** show that intelligence is fixed at birth. It does **not** mean education or policy are irrelevant. It does **not** allow easy prediction of an individual’s intelligence from DNA. And it does **not** by itself explain average differences between social, ethnic, national, or racial groups.

Heritability within a population says little about the causes of differences between populations. For example, height is highly heritable within countries, yet average height differences between countries can be largely environmental.

## Bottom line

Human intelligence is **moderately to highly heritable**, especially in adulthood. The strongest estimate is that **genetic differences account for roughly half or more of individual differences in intelligence in many modern, industrialized populations**, with adult estimates often around **60–80%**. This conclusion is supported by twin, adoption, and molecular genetic evidence.

But intelligence is also shaped by environments, development, education, health, and chance. Heritability means genes matter; it does not mean environment does not.


prompt_id: sci-iq-heritability

provider: openai

text:
Human intelligence, as measured by standardized cognitive tests and the general cognitive factor often called *g*, is **substantially heritable**, but it is also strongly influenced by environment. The short version:

> **In modern, relatively affluent populations, heritability of intelligence is often estimated around 40–60% in childhood/adolescence and around 60–80% in adulthood.**
> Molecular genetic studies usually find lower “SNP heritability,” roughly **20–30%**, because they capture only part of genetic variation.

Those numbers do **not** mean intelligence is fixed, unaffected by environment, or that group differences are genetic. Heritability is about variation *within a particular population in a particular environment*.

## What “heritability” means

Heritability is the proportion of differences among people in a given population that is statistically associated with genetic differences.

If adult IQ has heritability of 0.6, that means roughly 60% of the *variation among individuals* in that population is associated with genetic variation. It does **not** mean:

- “60% of a person’s intelligence is genetic”
- intelligence cannot be changed
- environment is unimportant
- genetic causes explain differences between populations or social groups

For example, height is highly heritable in many countries, but average height has changed a lot over time due to nutrition, disease burden, and living conditions. Intelligence shows a similar pattern: individual differences can be heritable while population averages can be environmentally shifted.

## Main evidence

### 1. Twin studies

Twin studies compare identical twins, who share nearly all their DNA, with fraternal twins, who share on average about half of their segregating DNA.

Typical findings:

- Identical twins are more similar in IQ than fraternal twins.
- Identical twins reared apart are still substantially similar.
- Fraternal twins and ordinary siblings are less similar than identical twins.

This pattern supports a genetic contribution.

Approximate estimates from twin research:

| Age | Typical heritability estimate |
|---|---:|
| Early childhood | ~20–40% |
| Middle childhood/adolescence | ~40–60% |
| Adulthood | ~60–80% |

One robust finding is that heritability of cognitive ability tends to **increase with age**. This may happen because as people grow older, they increasingly select and shape environments that fit their genetic tendencies — for example, choosing books, friends, hobbies, academic paths, and careers that reinforce cognitive strengths.

### 2. Adoption studies

Adoption studies compare adopted children with their biological and adoptive relatives.

Common findings:

- In childhood, adopted children’s IQs often resemble both adoptive and biological family environments.
- By adulthood, resemblance to biological relatives tends to increase.
- Resemblance to adoptive siblings often decreases with age.

This suggests that shared family environment matters, especially in childhood, but genetic influences become more apparent over development.

### 3. Molecular genetic studies

Modern genome-wide association studies, or GWAS, examine millions of genetic markers across many people.

Findings:

- Intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with tiny effect.
- There are no single “intelligence genes” of large effect in the normal range.
- Common genetic variants measured by SNP arrays explain roughly **20–30%** of variation in cognitive ability in many studies.
- Polygenic scores can predict some variation in cognitive performance and educational attainment, but prediction is still limited — often explaining single-digit to low-teens percentages of variance depending on trait, dataset, ancestry, and measurement.

Molecular evidence supports the twin-study conclusion that genetics matters, but it also shows that the genetic architecture is extremely diffuse and probabilistic.

## Environmental evidence

Even if intelligence is heritable, environmental effects are large and well documented.

Important environmental influences include:

- quality and quantity of schooling
- childhood nutrition
- prenatal environment
- lead and other neurotoxin exposure
- infectious disease burden
- stress, deprivation, and neglect
- sleep, health, and stimulation
- socioeconomic conditions
- access to books, language, and cognitively demanding activities

Several lines of evidence show environmental effects:

### Schooling

Additional schooling tends to raise measured cognitive performance. Natural experiments involving changes in compulsory schooling laws suggest that education can have causal effects on IQ-like test scores.

### The Flynn effect

Across much of the 20th century, average IQ test scores rose substantially in many countries — often by about 2–3 points per decade, though trends vary by country and era. Genetic change cannot explain such rapid population-level increases. Likely contributors include education, nutrition, urbanization, smaller families, more cognitively complex environments, and improved health.

### Deprivation and intervention

Severe deprivation, malnutrition, lead exposure, and poor schooling can depress cognitive development. Conversely, improved environments can raise outcomes, especially when interventions are early, sustained, and broad.

## Shared vs nonshared environment

Behavioral genetic studies often divide environmental influence into:

- **Shared environment**: factors making siblings similar, such as family socioeconomic status, neighborhood, and parenting style.
- **Nonshared environment**: factors making siblings different, such as different peer groups, illnesses, teachers, random developmental events, and differential treatment.

For intelligence:

- Shared environment is usually more important in childhood.
- Its estimated influence often declines by adulthood in affluent populations.
- Nonshared environment and measurement error remain meaningful across life.

However, in harsher or more unequal environments, shared environmental factors may play a larger role.

## Gene–environment interplay

Genes and environments are not separate, independent forces. They interact and correlate.

Examples:

### Gene–environment correlation

A child with an early verbal aptitude may seek books, receive more encouragement, and be placed in advanced classes. Genetic tendencies partly influence the environment the child experiences.

### Gene–environment interaction

The effect of genetic differences may depend on environment. For instance, genetic potential may be more fully expressed in environments with adequate nutrition, safety, schooling, and opportunity. In deprived environments, environmental constraints can suppress individual differences.

Evidence on socioeconomic status moderation is mixed: some studies, especially in the U.S., suggest heritability is lower in poorer environments; other studies, especially in countries with stronger social supports, find weaker or no such pattern.

## What the evidence does *not* show

The evidence does not show that intelligence is immutable. Heritable traits can be changed by environmental intervention.

It also does not justify using genetics to rank individuals rigidly. Polygenic scores are probabilistic, population-dependent, and far from deterministic.

And importantly, heritability estimates within a population do **not** explain average differences between groups. A trait can be highly heritable within groups while differences between groups are caused by environment. Human populations also differ in social history, education, discrimination, health, wealth, and exposure to environmental risks, making simplistic genetic explanations scientifically unwarranted.

## Bottom line

The best-supported view is:

- Human intelligence is **moderately to highly heritable**, especially by adulthood.
- Genetic influence is spread across thousands of variants of tiny effect.
- Environment has large effects, particularly through education, health, nutrition, deprivation, and opportunity.
- Heritability is population-specific and does not imply genetic determinism.
- Intelligence develops through continuous interaction between genetic propensities and environmental conditions.

finish_reason: stop


text:
Human intelligence—as measured by standardized cognitive tests such as IQ—is **substantially heritable**, but not genetically fixed. The best evidence suggests that **genetic differences explain a meaningful share of individual differences in cognitive ability within a given population**, while environment also matters a great deal.

## Short answer

- **Heritability of intelligence is often estimated around ~50% in adulthood**, with estimates commonly ranging from **40–80%** depending on age, population, methods, and environment.
- In **childhood**, heritability is lower, often around **20–40%**.
- Heritability tends to **increase with age**, while the influence of the shared family environment often decreases.
- Intelligence is **highly polygenic**: thousands of genetic variants each have tiny effects.
- Heritability does **not** mean intelligence is unchangeable, genetically determined, or that environment is unimportant.

## What “heritability” means

Heritability is a statistic about **variation within a population**. If IQ has a heritability of 50%, that means that, in that population and environment, about half of the differences among people in measured intelligence are statistically associated with genetic differences.

It does **not** mean:

- “50% of a person’s intelligence is genetic”
- intelligence cannot be improved
- environment does not matter
- differences between social groups are genetic
- genes determine an individual’s destiny

Heritability can change depending on nutrition, schooling, inequality, disease burden, test quality, and other environmental conditions.

## Main lines of evidence

### 1. Twin studies

Twin studies compare identical twins, who share nearly all their DNA, with fraternal twins, who share about half of their segregating DNA.

A consistent finding is:

- **Identical twins are more similar in IQ than fraternal twins**
- identical twins reared apart are still substantially similar
- similarity increases from childhood to adulthood

This pattern supports a genetic contribution to cognitive differences.

However, twin studies depend on assumptions, such as whether identical and fraternal twins experience equally similar environments. Researchers have debated these assumptions, but the broad result—some substantial genetic influence—has held up across many studies.

### 2. Adoption studies

Adoption studies compare children with their biological and adoptive relatives.

Typical findings:

- In childhood, adopted children’s IQ scores often resemble their **adoptive family environment** to some degree.
- As adopted individuals grow older, their cognitive scores tend to become more similar to those of their **biological relatives**.
- The shared family environment appears to matter more earlier in life and less in adulthood.

This does not mean parenting or schooling are unimportant. Rather, it suggests that by adulthood, family-level environmental differences explain less of the remaining variation in measured IQ in many studied populations.

### 3. Molecular genetic studies

Modern genome-wide association studies, or GWAS, look directly at DNA markers across very large samples.

They show that:

- intelligence and educational attainment are influenced by **many thousands of genetic variants**
- each individual variant has a tiny effect
- genetic prediction is possible but still limited
- measured SNP-based heritability is usually lower than twin-study heritability, often roughly **20–30%** for cognitive ability depending on the trait and sample

Polygenic scores can predict some differences in educational attainment and cognitive performance, but they are far from deterministic and are less accurate across ancestries and social contexts.

## Why heritability increases with age

A common finding is that intelligence becomes more heritable from childhood into adulthood. Possible reasons include:

1. **Genetic amplification**: small genetic differences influence interests, motivation, learning speed, and choices, which accumulate over time.
2. **Gene–environment correlation**: people increasingly select or create environments that fit their dispositions.
3. **Reduced shared-family effects**: as people leave the childhood home, siblings’ environments diverge.
4. **Measurement stability**: cognitive ability is measured more reliably in older children and adults.

## Environmental effects are still important

High heritability does not imply low environmental importance. Some environmental influences on intelligence include:

- quality and duration of schooling
- early childhood health and nutrition
- prenatal environment
- exposure to lead and other toxins
- sleep, stress, and disease
- socioeconomic conditions
- educational resources
- severe deprivation or neglect

The **Flynn effect**—large IQ-score gains across many countries during the 20th century—is strong evidence that environmental changes can substantially affect measured cognitive performance over time.

## Important caveats

### Heritability is population-specific

A heritability estimate from one country or era may not apply elsewhere. In an environment where everyone has similar nutrition and schooling, genetic differences may explain more of the remaining variation. In a harsher or more unequal environment, environmental differences may explain more.

### It says little about group differences

Heritability within a population does not explain average differences between populations or social groups. For example, height is highly heritable, but average height differences between generations or countries can be strongly environmental due to nutrition and health.

### Intelligence is not one single thing

IQ tests measure a broad cluster of cognitive abilities—reasoning, memory, processing speed, verbal ability, spatial ability—and these are positively correlated. But intelligence is not the entirety of human ability, achievement, creativity, wisdom, or worth.

## Bottom line

The evidence from twin, adoption, and DNA-based studies converges on the conclusion that **human intelligence is moderately to highly heritable**, especially in adulthood. A reasonable summary is:

- **Childhood IQ:** roughly **20–40% heritable**
- **Adult IQ:** often roughly **50% or more heritable**, with estimates varying by study and population
- **Environment:** still substantial, especially through education, health, nutrition, deprivation, and social conditions
- **Genetic architecture:** highly polygenic, with no “intelligence gene”

So the best answer is: intelligence is significantly influenced by genetics, but it is also shaped by environment, development, and social context.


text:
Human intelligence—as measured by IQ tests and related cognitive ability tests—is **substantially heritable**, but **not genetically fixed**. The best evidence suggests that, in many studied populations, genetic differences account for roughly **40–80% of individual differences in adult cognitive ability**, with estimates usually lower in childhood and higher in adulthood.

## What “heritable” means

Heritability is the proportion of **variation among individuals in a particular population and environment** that is statistically associated with genetic differences.

It does **not** mean:

- “80% of a person’s intelligence is genetic”
- intelligence is immutable
- environments do not matter
- heritability estimates apply equally across all societies or historical periods

A trait can be highly heritable and still strongly affected by environment. Height is a good analogy: it is highly heritable in well-nourished populations, but nutrition can still greatly affect average height.

## Typical heritability estimates

Evidence from twin, family, adoption, and genomic studies suggests approximately:

| Age/stage | Approximate heritability of cognitive ability |
|---|---:|
| Early childhood | ~20–40% |
| Middle childhood/adolescence | ~40–60% |
| Adulthood | ~50–80% |

A commonly cited summary is that **adult general intelligence is about 50–70% heritable** in many Western samples.

Heritability tends to increase with age partly because people increasingly select, shape, and respond to environments in ways correlated with their genetic dispositions — for example, choosing intellectually stimulating hobbies, courses, peers, or occupations.

## Main lines of evidence

### 1. Twin studies

Twin studies compare resemblance between:

- identical twins, who share ~100% of their segregating DNA
- fraternal twins, who share ~50% on average

Identical twins are usually much more similar in IQ than fraternal twins, including when raised apart, which supports a genetic contribution.

Classic findings:

- identical twins raised together: very high IQ correlations
- identical twins raised apart: still substantially correlated
- fraternal twins and ordinary siblings: less similar

Twin studies are not perfect, but the pattern has been replicated many times.

### 2. Adoption studies

Adoption studies show that adopted children often resemble their biological parents more as they age, while resemblance to adoptive parents tends to decline for cognitive ability.

This supports genetic influence, but also shows environmental effects, especially in childhood. Adoptive homes are often more socioeconomically advantaged and less variable than the general population, which can affect estimates.

### 3. Family studies

Relatives resemble each other in cognitive ability roughly in proportion to their genetic relatedness, though shared environment and social factors also contribute.

For example:

- siblings are more similar than cousins
- parent-child resemblance increases as children mature
- assortative mating matters: people tend to choose partners with similar education/cognitive traits, which can increase resemblance among siblings

### 4. DNA-based studies

Modern genomic studies examine measured DNA directly rather than relying only on family relationships.

They find that many genetic variants are associated with cognitive performance, each with tiny effects. Intelligence is **highly polygenic**: influenced by thousands of variants, not by a few “intelligence genes.”

Key points:

- SNP-based heritability estimates are often around **20–30%** for intelligence, sometimes higher depending on methods and samples.
- This is lower than twin-based estimates because common SNP methods miss some genetic effects, such as rare variants, structural variants, non-additive effects, and imperfect tagging.
- Polygenic scores can predict some variation in cognitive or educational outcomes, but they are far from deterministic.

For example, polygenic scores for educational attainment often predict a meaningful but limited fraction of variance in education, and somewhat less for direct IQ measures.

## Environmental effects are also real

Even when heritability is high, environment matters. Important environmental influences include:

- prenatal health
- childhood nutrition
- exposure to toxins such as lead
- disease burden
- schooling quality
- family stress and deprivation
- sleep, mental health, and cognitive stimulation
- poverty and social instability

The **Flynn effect**—the large rise in average IQ scores over the 20th century in many countries—strongly demonstrates environmental influence. Gene frequencies did not change fast enough to explain those gains.

Severe deprivation can substantially depress cognitive development, while improved health, nutrition, schooling, and safety can raise population averages.

## Heritability can differ by social context

Heritability estimates are not universal constants.

In environments where basic needs are met and educational opportunities are broadly available, genetic differences may explain more of the remaining variation. In harsher or more unequal environments, environmental constraints may suppress genetic potential, lowering observed heritability.

Some studies have found that heritability of IQ is lower among children in low-socioeconomic-status environments, especially in the United States, though results vary by country and cohort.

## What the evidence shows overall

The evidence supports several conclusions:

1. **Human cognitive ability is meaningfully heritable.**
   Genetic differences contribute substantially to why people differ in measured intelligence.

2. **The trait is polygenic.**
   There is no single gene for intelligence; many genetic variants each have tiny effects.

3. **Heritability increases with age.**
   Genetic influence tends to become more apparent from childhood to adulthood.

4. **Environment still matters greatly.**
   Education, health, nutrition, toxins, stress, and social conditions can all affect cognitive development.

5. **Heritability is about variation within populations, not destiny.**
   A high heritability estimate does not imply that individuals cannot change or that interventions are useless.

6. **Group differences require separate evidence.**
   Heritability within a population does not automatically explain differences between populations or social groups.

In short: **adult intelligence is substantially heritable, often estimated around 50–70%, but it is also strongly shaped by environment, development, and social conditions.**


text:
Human intelligence, as measured by IQ tests and related cognitive batteries, is **substantially heritable**, but not genetically fixed. The best evidence suggests that in modern, relatively affluent populations, **genetic differences account for roughly 50–70% of variation in adult cognitive ability**, with lower estimates in childhood and in more deprived environments.

## What “heritability” means

Heritability is the proportion of **differences among people in a particular population at a particular time** that can be statistically associated with genetic differences.

It does **not** mean:

- “70% of a person’s intelligence is genetic.”
- Intelligence cannot be changed.
- Environment is unimportant.
- The same estimate applies to all societies or historical periods.

A trait can be highly heritable and still strongly affected by environment. For example, height is highly heritable, but nutrition and disease still matter greatly.

## Typical estimates

Across many twin, adoption, family, and molecular genetic studies:

- **Early childhood:** heritability often around **20–40%**
- **Middle childhood/adolescence:** around **40–60%**
- **Adulthood:** often around **50–80%**, commonly summarized as about **50–70%**

The heritability of general cognitive ability tends to **increase with age**. One likely reason is that as people grow older, they increasingly select, shape, and evoke environments that match their genetic predispositions—through interests, schooling choices, peer groups, reading habits, occupations, and so on.

## Main lines of evidence

### 1. Twin studies

Identical twins share essentially all their genetic variants, while fraternal twins share about half, on average.

A common finding is:

- Identical twins have much more similar IQ scores than fraternal twins.
- Identical twins reared apart are still substantially similar.
- Fraternal twins and ordinary siblings are less similar.

This pattern supports a genetic contribution.

However, twin studies depend on assumptions about environmental similarity, so they are not perfect. Still, their findings are broadly consistent with adoption and DNA-based evidence.

### 2. Adoption studies

Adoption studies show that children’s IQ scores are influenced by both adoptive environments and biological ancestry.

Typical findings:

- In childhood, adopted children often resemble their adoptive families to some extent.
- As they age, their cognitive scores tend to become more similar to those of their biological relatives.
- The effect of the shared family environment often declines from childhood into adulthood.

This suggests that family environment matters, especially early on, but genetic influences become more apparent with age.

### 3. Genome-wide association studies

Modern DNA studies show that intelligence-related traits are influenced by **many thousands of genetic variants**, each with very small effects. There is no single “intelligence gene.”

Genome-wide studies find that common genetic variants explain a meaningful but incomplete portion of IQ variation. Estimates of **SNP heritability**—the variance captured by measured common variants—are often around **20–30%**, lower than twin-study estimates because they miss rare variants, non-additive effects, and some other genetic influences.

Polygenic scores can predict some cognitive and educational outcomes, but their predictive power is still limited and depends heavily on ancestry, social context, and study design.

## Environment still matters a lot

Even if adult IQ is substantially heritable, environmental factors are important. Examples include:

- Prenatal health
- Nutrition
- Exposure to toxins such as lead
- Childhood disease burden
- Quality of schooling
- Cognitive stimulation
- Stress and trauma
- Sleep
- Family resources
- Social inequality

The **Flynn effect**—the large rise in IQ scores over the 20th century in many countries—shows that population-level cognitive test performance can change substantially over time, far too quickly to be explained by genetic evolution. This is strong evidence for environmental influence.

## Heritability depends on social conditions

Heritability is often higher when environments are relatively equal and supportive, because environmental barriers are reduced and genetic differences account for more of the remaining variation.

In contrast, in settings with severe poverty, poor schooling, malnutrition, or high toxin exposure, environmental constraints can suppress cognitive development and reduce the apparent heritability of intelligence.

So the question is not “genes or environment?” but rather **how genes and environments interact**.

## Bottom line

The evidence shows that human intelligence is **moderately to highly heritable**, especially in adulthood, with typical estimates around **50–70%** in many developed populations. But intelligence is also strongly shaped by environment, especially early in life and under conditions of deprivation. Heritability does not imply immutability, and it does not mean that social, educational, nutritional, or health interventions are unimportant.


text:
Human intelligence—as measured by standardized cognitive tests and often summarized as general cognitive ability, or **g**—is **substantially heritable**, but not genetically determined. The best evidence suggests that genetic differences explain a meaningful share of differences in intelligence **within a given population and environment**, while environment also matters a great deal.

## Short answer

Across many studies, the heritability of intelligence is roughly:

- **Childhood:** about **20–40%**
- **Adolescence:** about **40–60%**
- **Adulthood:** often **50–80%**

A commonly cited adult estimate is around **60%**, though estimates vary by age, population, test, and environment.

“Heritable” here means: *in a particular population at a particular time, what proportion of individual differences can be statistically associated with genetic differences?* It does **not** mean that an individual’s intelligence is fixed, nor that environment is unimportant.

---

## What evidence supports this?

### 1. Twin studies

Twin studies compare identical twins, who share nearly all their DNA, with fraternal twins, who share about half of their segregating genetic variation.

A consistent finding is:

- Identical twins are more similar in IQ than fraternal twins.
- Identical twins reared apart are still notably similar.
- Fraternal twins are more similar than ordinary siblings, partly because they share age and family environment.

These patterns imply a genetic contribution.

Typical correlations are roughly:

- **Identical twins reared together:** high similarity, often around **0.80+**
- **Fraternal twins reared together:** lower, often around **0.50–0.60**
- **Identical twins reared apart:** still substantial, often around **0.60–0.70**

The exact numbers vary, but the overall pattern is robust.

---

### 2. Adoption studies

Adoption studies examine whether adopted children resemble their biological or adoptive relatives.

Findings generally show:

- In early childhood, adopted children resemble both adoptive and biological families to some extent.
- As they grow older, resemblance to **biological relatives** tends to increase.
- Resemblance to **adoptive relatives** for IQ often decreases by adulthood.

This suggests that genetic influence becomes more visible with age, while the effect of the shared family environment on IQ differences often weakens over time.

---

### 3. Molecular genetics and GWAS

Modern genome-wide association studies, or GWAS, look directly at DNA variants across very large samples.

These studies show that intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with extremely small effects.

Key findings:

- Common genetic variants captured by SNP arrays explain perhaps **20–30%** of variation in cognitive ability, depending on sample and method.
- Polygenic scores can predict some differences in educational attainment and cognitive performance, but their predictive power is still limited.
- Known DNA variants explain less than classical twin-study heritability estimates, a gap sometimes called “missing heritability.”

Molecular evidence strongly supports genetic influence, but also shows that there is no single “intelligence gene.”

---

## Why does heritability increase with age?

This is one of the more interesting findings. Intelligence heritability tends to rise from childhood into adulthood.

Possible reasons include:

1. **Gene–environment correlation**
   As people get older, they increasingly choose, shape, and evoke environments that fit their genetic tendencies. For example, a child who enjoys reading may read more, which further develops verbal ability.

2. **Reduced shared environmental control**
   Young children are more constrained by family and school environments. Adults have more autonomy.

3. **Amplification over time**
   Small early differences in ability, motivation, temperament, or attention can compound through education and experience.

---

## Environment still matters a lot

High heritability does not mean environment is unimportant.

Environmental factors that can affect cognitive development include:

- Nutrition
- Prenatal health
- Exposure to toxins such as lead
- Childhood disease burden
- Stress and trauma
- Sleep
- Quality of schooling
- Family resources and stimulation
- Social stability and safety

The **Flynn effect**—the large rise in IQ scores over the 20th century in many countries—shows that environmental changes can substantially shift population-level test performance over time, even when heritability within a generation is high.

---

## Important caveats

### Heritability is population-specific

A heritability estimate applies to a particular population in a particular range of environments. If environments become more equal, genetic differences may explain a larger share of remaining variation. If environments become more unequal or deprived, environmental differences may explain more.

### Heritability does not apply straightforwardly to group differences

Heritability within a population does **not** tell us whether differences between populations, countries, ethnic groups, or social classes are genetic. A trait can be highly heritable within groups while group differences are entirely environmental.

For example, height is highly heritable, but average height differences between countries can be strongly influenced by nutrition and health.

### IQ tests measure important but not exhaustive abilities

IQ and general cognitive ability predict many outcomes—educational achievement, job performance, health behaviors, and longevity—but they do not capture all valuable human capacities, such as creativity, wisdom, emotional skill, practical knowledge, or character.

---

## Bottom line

The evidence from twin, adoption, family, and molecular genetic studies shows that human intelligence is **moderately to highly heritable**, especially in adulthood. A reasonable summary is:

> Genetic differences account for roughly half or more of the variation in adult intelligence within many studied populations, while environmental factors remain crucial and can strongly influence both individual development and population-level outcomes.

So intelligence is neither “all genetic” nor “all environmental.” It is shaped by many genes interacting with many environments over time.


text:
Human intelligence, as measured by IQ tests and related cognitive batteries, is **substantially heritable**, but it is **not genetically fixed**. The best evidence suggests that genetic differences explain a sizable share of differences in cognitive ability **within a given population and environment**, while environment also matters a great deal.

## Short answer

In contemporary industrialized populations:

- **Childhood IQ heritability:** roughly **20–50%**
- **Adolescent/adult IQ heritability:** roughly **50–80%**
- **Shared family environment:** often important in childhood, usually smaller by adulthood
- **Non-shared environment, schooling, health, nutrition, chance developmental factors, and measurement error:** also contribute substantially

A common summary is: **about half or more of adult variation in intelligence is associated with genetic differences**, but this varies by age, society, socioeconomic conditions, and measurement method.

## What “heritability” means

Heritability is often misunderstood. It does **not** mean:

- “80% of a person’s intelligence is genetic”
- “IQ cannot be changed”
- “Genetic differences explain differences between social groups”
- “Environment does not matter”

Rather, heritability means:

> In a particular population, at a particular time, under a particular range of environments, what proportion of variation among individuals is statistically associated with genetic variation?

So if adult IQ heritability is estimated at 60%, that means **60% of the observed differences between people in that population** are associated with genetic differences. It says nothing directly about any one individual’s potential.

## Main evidence

### 1. Twin studies

Twin studies compare identical twins, who share nearly all their DNA, with fraternal twins, who share about half of their segregating DNA.

Findings are consistent:

- Identical twins are more similar in IQ than fraternal twins.
- Identical twins reared apart are still substantially similar.
- Heritability estimates increase from childhood to adulthood.

Typical correlations:

- Identical twins reared together: often around **0.75–0.85**
- Fraternal twins reared together: often around **0.40–0.60**
- Identical twins reared apart: often around **0.60–0.75**

These patterns strongly suggest a genetic contribution.

### 2. Adoption studies

Adoption studies compare adopted children with their biological and adoptive families.

Typical findings:

- In childhood, adopted children’s IQs are influenced by the adoptive home environment.
- As children grow older, their cognitive scores tend to correlate more with biological relatives than adoptive relatives.
- Adoption into more advantaged homes can raise IQ, especially when children come from deprived conditions.

This supports both genetic influence and environmental influence.

### 3. Molecular genetics

Genome-wide association studies, or GWAS, have identified many DNA variants associated with cognitive performance and educational attainment.

Key findings:

- Intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with tiny effects.
- Measured common genetic variants account for a meaningful but incomplete portion of intelligence variation.
- Current polygenic scores can predict some variation in cognitive ability and education, but far from all of it.

Approximate figures:

- SNP-based heritability for intelligence is often estimated around **20–30%**, sometimes higher depending on method and sample.
- Polygenic scores currently explain perhaps **5–15%** of variance in cognitive performance in some samples, more for educational attainment in certain datasets.

These estimates are lower than twin-study heritability because GWAS captures only measured common variants well and misses some rare variants, structural variants, gene–gene interactions, and other sources.

## Heritability changes with age

One of the most replicated findings is that IQ heritability tends to **increase with age**.

A rough pattern:

| Age | Approximate heritability |
|---|---:|
| Early childhood | 20–40% |
| Middle childhood | 40–50% |
| Adolescence | 50–70% |
| Adulthood | 60–80% |

Why might heritability rise?

One explanation is **gene–environment correlation**. As people mature, they increasingly select, shape, and evoke environments that fit their dispositions. For example, a child with a genetic tendency toward verbal ability may read more, seek intellectually stimulating peers, and receive more encouragement, amplifying initial differences.

## Environment still matters a lot

Even when heritability is high, environmental effects can be large.

Evidence for environmental influence includes:

- The **Flynn effect**: average IQ scores rose substantially across many countries during the 20th century, too quickly to be genetic.
- Schooling improves measured cognitive performance.
- Severe deprivation, malnutrition, lead exposure, chronic stress, poor sleep, disease burden, and lack of educational opportunity can reduce cognitive development.
- Adoption from deprived to enriched environments can produce large gains.
- Early childhood interventions sometimes improve cognitive and educational outcomes, though IQ gains may fade if environments remain poor.

So high heritability does not imply immutability. Height is highly heritable, but nutrition and disease still strongly affect height.

## Heritability depends on social context

Heritability is not a universal constant.

In environments where nutrition, schooling, health care, and safety are broadly available, remaining variation may be more strongly associated with genetic differences. In harsher or more unequal environments, environmental constraints may suppress genetic potential.

Some studies have found that IQ heritability is lower among children in poverty, especially in the United States, though this finding is not equally strong across all countries. In more equal welfare states, socioeconomic moderation of heritability appears weaker.

## Intelligence is not a single simple trait

“Intelligence” includes multiple related abilities:

- reasoning
- working memory
- processing speed
- vocabulary
- spatial ability
- quantitative ability
- general cognitive ability, often called **g**

The general factor, **g**, is usually highly heritable, but specific abilities also have genetic and environmental components.

## Important cautions

### Heritability within groups does not explain between-group differences

A high heritability estimate within a population does **not** tell us why two groups differ in average test scores. Group differences can be caused by environmental differences even when individual differences within groups are heritable.

Example: height is highly heritable within populations, yet average height differences between countries have changed dramatically due to nutrition and health.

### Heritability is not destiny

Genes influence probability, not certainty. Cognitive outcomes are affected by education, health, family environment, culture, motivation, personality, and opportunity.

### IQ tests are useful but imperfect

IQ tests predict many life outcomes, including academic achievement and job performance, but they do not capture all valuable mental traits, such as creativity, wisdom, practical skills, emotional understanding, or motivation.

## Bottom line

The evidence from twin, adoption, family, and molecular genetic studies shows that human intelligence is **moderately to highly heritable**, especially in adulthood. A reasonable broad estimate is that **genetic differences account for about 50–70% of adult variation in intelligence in many modern developed populations**, with lower estimates in childhood.

However, intelligence is also meaningfully shaped by environment. Heritability does not mean fixed, inevitable, or unaffected by policy and life experience. It means that, within studied populations, genetic differences are an important part of why people differ in measured cognitive ability.


text:
Human intelligence is **substantially heritable**, but heritability is often misunderstood. In modern behavioral genetics, “heritability” means the proportion of **variation among individuals within a particular population and environment** that is statistically associated with genetic differences. It does **not** mean intelligence is fixed, unaffected by environment, or that group differences are genetic.

## Short answer

Across many studies, the heritability of measured cognitive ability/IQ is roughly:

- **Childhood:** about **30–50%**
- **Adolescence:** about **40–60%**
- **Adulthood:** often **50–80%**, with many estimates around **60%**
- **Older adulthood:** still substantial, though health and aging environments also matter

The rest of the variation reflects **environmental factors, measurement error, developmental randomness, gene–environment interplay**, and other non-genetic influences.

## What evidence supports this?

### 1. Twin studies

Twin studies compare similarity between:

- **Identical twins**, who share ~100% of their DNA
- **Fraternal twins**, who share ~50% on average

If identical twins are more similar in IQ than fraternal twins, that suggests genetic influence.

A common finding is that identical twins are much more similar in cognitive test scores than fraternal twins. This pattern appears across many countries and samples.

Typical correlations are roughly:

- Identical twins raised together: **~0.75–0.85**
- Fraternal twins raised together: **~0.40–0.60**
- Identical twins raised apart: often **~0.65–0.75**, though based on smaller samples

These results imply substantial genetic influence, especially by adulthood.

### 2. Adoption studies

Adoption studies examine whether adopted children resemble their biological or adoptive relatives.

Findings generally show:

- In early childhood, children’s IQs often resemble both adoptive family environment and biological family background.
- As children grow older, their IQ tends to become more correlated with biological parents’ IQ and less correlated with adoptive parents’ IQ.
- By adulthood, resemblance to adoptive siblings or adoptive parents in IQ is often small, while resemblance to biological relatives remains.

This supports the idea that genetic influence on cognitive ability increases with age, while shared family environment has stronger effects earlier in life.

### 3. Molecular genetic studies

Modern genome-wide association studies, or GWAS, look directly at DNA variants across many people.

They show that intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with tiny effects.

Important findings:

- Common measured DNA variants explain a meaningful but incomplete portion of IQ variation, often called **SNP heritability**.
- SNP heritability for cognitive ability is commonly estimated around **20–30%**, lower than twin-study heritability because GWAS captures only part of genetic influence.
- Polygenic scores constructed from GWAS can predict some variation in cognitive performance and educational attainment, but they are far from deterministic.
- Current polygenic scores explain only a modest fraction of individual differences, often on the order of **several percent to perhaps 10–15%** depending on phenotype, sample, and ancestry.

Molecular evidence confirms that genetic differences contribute to cognitive differences, but also shows the architecture is diffuse and probabilistic, not controlled by “intelligence genes” in any simple way.

## Heritability changes with age

One of the strongest findings is that heritability of intelligence tends to **increase from childhood to adulthood**.

This may seem counterintuitive, but several mechanisms can explain it:

1. **Gene–environment correlation**
   As people grow older, they increasingly select, shape, and create environments compatible with their dispositions and abilities. For example, a child who enjoys reading may seek out more books and intellectual activities.

2. **Greater autonomy with age**
   Adults have more control over education, occupations, friends, and hobbies than children do.

3. **Shared family environment fades**
   Siblings raised in the same home may become less similar over time as they choose different paths.

## Environment still matters

High heritability does not mean environment is unimportant.

Environmental influences on intelligence include:

- Nutrition
- Prenatal health
- Childhood disease burden
- Exposure to toxins such as lead
- Quality of schooling
- Cognitive stimulation
- Family stress
- Sleep
- Neighborhood safety
- Socioeconomic conditions
- Access to books, language, and learning opportunities

Extreme deprivation, neglect, malnutrition, or poor schooling can substantially reduce cognitive development. Conversely, improved environments can raise population-level cognitive performance.

The **Flynn effect**—large IQ score gains over the 20th century in many countries—is strong evidence that environmental changes can shift average test performance substantially, even while individual differences within a given environment remain partly heritable.

## Heritability depends on the population and environment

Heritability is not a universal constant.

For example:

- In relatively equal, affluent environments, genetic differences may account for a larger share of remaining individual variation.
- In deprived or highly unequal environments, environmental constraints may suppress genetic potential, reducing heritability.
- Estimates can vary by country, cohort, age, test type, and socioeconomic context.

So saying “IQ is 60% heritable” is shorthand for a particular type of population estimate, not a timeless biological law.

## What about specific abilities?

General cognitive ability, often called **g**, is consistently heritable. Specific abilities such as verbal ability, spatial reasoning, memory, and processing speed are also heritable, though estimates vary.

Genes that influence one cognitive domain often influence others too. This is called **genetic overlap** or pleiotropy, and it helps explain why different mental abilities tend to correlate.

## What heritability does not mean

Heritability does **not** mean:

- Intelligence is fixed.
- Education is pointless.
- A person’s IQ is “60% genetic.”
- Group differences are genetic.
- Genetic influence cannot be changed by policy or intervention.
- DNA can accurately predict an individual’s intellectual potential.

A highly heritable trait can still be environmentally influenced. For example, height is highly heritable in well-nourished populations, yet average height can increase dramatically with better nutrition and health.

## Bottom line

The evidence from twin, adoption, family, and DNA-based studies shows that **human intelligence is moderately to highly heritable**, especially in adulthood. A reasonable summary is that genetic differences explain **about half or more** of individual differences in measured intelligence in many contemporary adult populations.

But intelligence is also shaped by environment, development, education, health, culture, and chance. Heritability describes variation within a population; it does not imply immutability, inevitability, or genetic explanations for differences between social groups.


text:
Human intelligence—as measured by IQ and related cognitive tests—is **substantially heritable**, but not genetically fixed. The best evidence suggests that genetic differences explain a sizeable share of **individual differences within a given population and environment**, while environment also matters, especially in childhood.

## Short answer

- In **childhood**, heritability of IQ is often estimated around **20–50%**.
- By **adulthood**, estimates commonly rise to about **50–80%**, with many reviews placing adult IQ heritability near **60–70%**.
- Modern DNA-based methods usually produce lower estimates, often around **20–30% “SNP heritability”**, because they capture only the effects of common genetic variants measured in genome-wide studies.
- Intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with tiny effects.
- Heritability does **not** mean immutability, does **not** apply to individuals, and does **not** explain differences between populations or social groups.

## What “heritability” means

Heritability is the proportion of variation in a trait, within a particular population at a particular time, associated with genetic differences.

So if adult IQ has a heritability of 60%, that means:

> About 60% of the differences among people in that population, under those environmental conditions, are statistically associated with genetic differences.

It does **not** mean:

- “60% of a person’s intelligence is genetic.”
- “Environment does not matter.”
- “IQ cannot be changed.”
- “Group differences are genetic.”
- “Genes determine destiny.”

A trait can be highly heritable and still be strongly affected by environment. For example, height is highly heritable, but nutrition and disease can greatly affect average height.

## Main lines of evidence

### 1. Twin studies

Twin studies compare identical twins, who share nearly 100% of their DNA, with fraternal twins, who share about 50% on average.

Findings are very consistent:

- Identical twins are more similar in IQ than fraternal twins.
- Identical twins reared apart are still substantially similar.
- Fraternal twins and ordinary siblings are less similar.

This supports a genetic contribution to intelligence.

Approximate pattern:

| Relationship | Typical IQ similarity |
|---|---:|
| Identical twins raised together | High |
| Identical twins raised apart | Moderately high |
| Fraternal twins/siblings raised together | Moderate |
| Adoptive siblings raised together | Lower, especially in adulthood |
| Unrelated people | Near zero |

Twin studies often produce adult heritability estimates in the **50–80%** range.

### 2. Adoption studies

Adoption studies ask whether adopted children resemble their biological or adoptive relatives more.

Typical findings:

- In childhood, adopted children’s IQs are influenced by the adoptive home environment.
- As they age, their IQs tend to become more similar to their biological relatives.
- The effect of shared family environment often decreases by adulthood.

This does **not** mean parenting or schooling are unimportant. It means that within the range of environments studied, shared family-level effects on adult IQ differences are often smaller than genetic and non-shared environmental effects.

### 3. Genome-wide association studies

Modern genetic studies scan DNA across hundreds of thousands or millions of people.

They find that:

- Many genetic variants are associated with cognitive ability or educational attainment.
- Each variant has a very small effect.
- Polygenic scores can predict some differences in cognitive performance, but far from perfectly.

DNA-based estimates are usually lower than twin-study estimates. For cognitive ability, common measured variants often account for something like **20–30%** of variation, depending on the sample and method. Polygenic scores currently predict a smaller fraction of individual IQ variation, often in the single digits to low teens.

This gap between twin-study heritability and measured DNA prediction is sometimes called “missing heritability.” It may reflect rare variants, structural variants, gene–gene interactions, imperfect measurement, and limitations of current datasets.

## Heritability changes with age

One of the most robust findings is that IQ heritability tends to **increase with age**.

This is sometimes called the **Wilson effect**.

A simplified pattern:

| Age | Approximate heritability |
|---|---:|
| Early childhood | 20–40% |
| Middle childhood | 30–50% |
| Adolescence | 40–60% |
| Adulthood | 50–80% |

Why might this happen?

Possible reasons include:

- People increasingly choose environments that fit their genetic tendencies.
- Children gain more control over friends, hobbies, education, and work.
- Small early differences can compound over time.
- Gene–environment correlation becomes stronger with age.

For example, a child with a genetic tendency toward verbal ability may read more, seek intellectually stimulating settings, and thereby further develop those abilities.

## Environment still matters

Environmental influences on intelligence include:

- Prenatal health
- Nutrition
- Exposure to toxins, such as lead
- Childhood disease burden
- Stress and trauma
- Sleep
- School quality
- Cognitive stimulation
- Family resources
- Social stability
- Cultural and linguistic context
- Access to books, technology, and education

Major environmental improvements can raise cognitive outcomes. The **Flynn effect**, the large rise in IQ scores across many countries during the 20th century, is strong evidence that environments can shift average cognitive performance substantially.

Also, severe deprivation can lower IQ, and interventions such as improved nutrition, early childhood education, and removal from neglectful environments can improve outcomes.

## Shared vs non-shared environment

Behavioral genetics often divides environmental effects into:

### Shared environment

Influences that make siblings similar:

- Family income
- Neighborhood
- Parenting style
- School district
- Household language

Shared environment appears to matter more in childhood and less in adulthood for IQ in many developed-country studies.

### Non-shared environment

Influences that make siblings different:

- Different peer groups
- Different teachers
- Illnesses or injuries
- Unique life experiences
- Measurement error
- Different treatment within the family

Non-shared environment remains important throughout life.

## Important cautions

### 1. Heritability is not universality

Heritability estimates depend on the population studied. If environments are very unequal, environmental effects may be larger. If environments are relatively equal, genetic differences may explain more of the remaining variation.

### 2. Heritability does not imply immutability

A highly heritable trait can still be changed. Poor eyesight is highly heritable, but glasses work. Phenylketonuria is genetic, but dietary intervention can prevent severe cognitive impairment.

### 3. Heritability within groups does not explain differences between groups

Even if IQ is substantially heritable within a population, that does not show that average differences between socioeconomic, ethnic, national, or racial groups are genetic. Group differences can be caused by environmental factors even when within-group heritability is high.

### 4. Intelligence is not a single simple trait

IQ tests measure a broad general cognitive factor, often called **g**, but intelligence includes multiple abilities:

- Reasoning
- Working memory
- Processing speed
- Verbal comprehension
- Spatial ability
- Learning ability
- Problem solving

These are correlated but not identical.

## Bottom line

The evidence from twin, adoption, family, and DNA studies shows that **human intelligence is moderately to highly heritable**, especially in adulthood. A reasonable summary is:

> Genetic differences account for roughly half or more of adult individual differences in intelligence in many studied populations, while environmental factors remain important and can substantially affect both individual development and population averages.

So intelligence is influenced by genes, environment, and their interaction—not by genes alone.


text:
Human intelligence, as measured by IQ tests and related cognitive batteries, is **substantially heritable**, but it is **not genetically fixed** and heritability estimates depend on age, environment, population, and measurement.

## Short answer

Across modern behavioral-genetic studies, the heritability of intelligence is usually estimated at roughly:

- **Childhood:** about **20–50%**
- **Adolescence:** about **40–60%**
- **Adulthood:** about **50–80%**

A common broad summary is that **around half or more of variation in adult intelligence within a given population is associated with genetic differences**. The rest is due to environmental influences, measurement error, developmental randomness, and gene–environment interplay.

Importantly, **heritability does not mean immutability**. Height is highly heritable, but nutrition still matters. Similarly, intelligence is heritable, but education, health, poverty, toxins, nutrition, stress, disease burden, and social conditions can strongly affect cognitive development.

---

## What “heritability” means

Heritability is a statistic describing **how much of the variation among individuals in a particular population, at a particular time, under particular environmental conditions, is associated with genetic differences**.

It does **not** mean:

- “X% of a person’s intelligence is genetic”
- “Intelligence cannot be changed”
- “Environmental interventions cannot work”
- “Genetic differences explain group differences”
- “IQ is determined by a single gene or a small number of genes”

For intelligence, heritability refers to differences **within populations**, not necessarily differences **between populations** or social groups.

---

## Evidence from twin and adoption studies

The strongest classical evidence comes from twin, adoption, and family studies.

### Twin studies

Identical twins share nearly 100% of their DNA, while fraternal twins share about 50% of their segregating DNA. If identical twins are more similar in IQ than fraternal twins, that suggests genetic influence.

Findings generally show:

- Identical twins are more similar in intelligence than fraternal twins.
- Twins reared apart are still substantially similar in IQ.
- Genetic influence tends to increase with age.

Typical correlations are roughly:

- Identical twins raised together: often around **0.75–0.85**
- Fraternal twins raised together: often around **0.40–0.60**
- Identical twins raised apart: often around **0.65–0.75**, though estimates vary

These patterns imply substantial genetic contribution.

### Adoption studies

Adoption studies also support genetic influence.

Common findings:

- Adopted children’s IQs in early childhood may resemble their adoptive families to some degree.
- As adoptees grow older, their IQs tend to become more similar to their biological relatives than to their adoptive relatives.
- Shared family environment appears more influential in childhood and less influential in adulthood.

This does not mean family environment is irrelevant; rather, the long-term variance in IQ among adults in many studied populations is less strongly explained by shared household environment than by genetics and non-shared environmental factors.

---

## Evidence from molecular genetics

Modern genome-wide association studies, or GWAS, have identified many genetic variants associated with cognitive ability and educational attainment.

Key points:

- Intelligence is **highly polygenic**: influenced by thousands of genetic variants, each with tiny effects.
- No single “intelligence gene” exists.
- SNP-based heritability estimates — the proportion of variance captured by common measured genetic variants — are typically lower than twin-study estimates, often around **20–30%** for cognitive ability, depending on sample and method.
- Polygenic scores can predict some variation in educational attainment and cognitive performance, but they are far from determinative.

For example, current polygenic scores may explain a modest fraction of variation — often in the range of several percent up to the low teens depending on the trait, population, and study design. They are useful scientifically but weak for individual prediction.

---

## Why heritability increases with age

One of the most replicated findings is that the heritability of intelligence tends to rise from childhood into adulthood.

Possible reasons include:

1. **Gene–environment correlation**
   As people age, they increasingly select, shape, and create environments that fit their genetic tendencies. A child with a genetic disposition toward verbal ability may read more, seek intellectual peers, and choose challenging classes, amplifying initial differences.

2. **Greater autonomy**
   Adults have more freedom than children to choose occupations, hobbies, education, and social contexts.

3. **Declining shared family influence**
   The common home environment matters more when children are young. Its relative contribution often decreases as individuals leave home and develop independent lives.

---

## Environmental effects are still very important

High heritability does not imply environment is unimportant. Environmental influences can have large effects on intelligence.

Examples include:

- Quality and length of schooling
- Childhood nutrition
- Prenatal health
- Exposure to lead or other neurotoxins
- Infectious disease burden
- Sleep, stress, and trauma
- Socioeconomic deprivation
- Parenting, language exposure, and cognitive stimulation
- Public health improvements

The **Flynn effect** is a major example: IQ scores rose substantially across many countries during the 20th century, too quickly to be caused by genetic evolution. This shows that broad environmental changes can shift average cognitive performance.

---

## Socioeconomic context may matter

Some studies, especially in the United States, have found that heritability of IQ is lower among children raised in poverty and higher among children in more advantaged environments. The interpretation is that severe deprivation can suppress genetic potential.

However, findings are mixed internationally. In some European and high-income welfare-state samples, this moderation by socioeconomic status is weaker or absent. This suggests that when basic environmental supports are more equalized, genetic differences may account for more of the remaining variation.

---

## Important limitations

The evidence is strong that genes contribute substantially to individual differences in intelligence, but there are caveats:

1. **Twin studies rely on assumptions**
   Such as the equal environments assumption: that identical and fraternal twins experience equally similar environments relevant to the trait. Researchers have tested this in various ways, and the genetic signal remains, but it is still a methodological issue.

2. **Heritability is population-specific**
   A heritability estimate from middle-class Sweden does not automatically apply to impoverished regions, historical populations, or societies with unequal schooling.

3. **Genetic influence includes indirect pathways**
   Genes may affect intelligence partly through temperament, curiosity, motivation, health, or the environments people evoke and select.

4. **Assortative mating matters**
   People tend to pair with partners similar in education and cognitive ability, which can affect genetic estimates.

5. **Tests do not measure every kind of intelligence**
   IQ and cognitive tests capture important general cognitive abilities, especially reasoning, working memory, processing speed, and verbal/spatial skills, but not every valuable human capacity.

---

## Bottom line

The evidence shows that human intelligence is **moderately to highly heritable**, especially in adulthood. A reasonable summary is:

> In contemporary developed populations, genetic differences explain roughly **half or more of the variation in adult intelligence**, while environmental factors and developmental influences explain the rest.

But this does **not** mean intelligence is fixed, purely genetic, or unaffected by policy. The best reading of the evidence is that intelligence emerges from a complex interplay of many genes and many environments over development.


prompt_id: sci-vaccines-safety

text:
Yes. **Recommended childhood vaccines are safe and effective at preventing serious diseases.** They are extensively tested before approval and continuously monitored for safety after they’re in use.

Vaccines protect children against illnesses such as measles, polio, whooping cough, meningitis, chickenpox, and others—many of which can cause hospitalization, long-term complications, or death. High vaccination rates also help protect infants too young to be vaccinated and people with weakened immune systems.

Most side effects are mild and temporary, such as:
- Soreness or redness where the shot was given
- Low-grade fever
- Fussiness or tiredness

Serious side effects are **very rare**, and the risks from the diseases vaccines prevent are generally much higher than the risks from vaccination.

If you have concerns about a specific vaccine or your child’s health situation, it’s best to talk with your pediatrician or a qualified healthcare professional.


text:
Yes. **Childhood vaccines are overwhelmingly safe and highly effective at preventing serious diseases.** They are among the most studied medical interventions and are continuously monitored for safety.

- **Effectiveness:** Vaccines have dramatically reduced or nearly eliminated diseases such as polio, measles, diphtheria, rubella, Hib meningitis, and whooping cough in places with high vaccination rates. They also reduce severe illness, hospitalizations, and deaths.
- **Safety:** Most side effects are mild and temporary, such as soreness at the injection site, low fever, or fussiness. Serious side effects are **very rare** and are monitored through national safety systems.
- **Community protection:** High vaccination rates help protect babies too young to be vaccinated and people with weakened immune systems.

The benefits of routine childhood vaccination greatly outweigh the risks for the vast majority of children. If your child has specific medical conditions, allergies, or a history of reactions, it’s best to discuss the vaccine schedule with a pediatrician.


text:
Yes. **Childhood vaccines are safe and highly effective at preventing serious diseases.** They are one of the most successful public health tools ever developed and have dramatically reduced illnesses such as measles, polio, diphtheria, whooping cough, Hib meningitis, and many others.

Key points:

- **Effectiveness:** Vaccines train the immune system to recognize and fight specific infections. Many childhood vaccines provide very strong protection against severe disease, hospitalization, and death.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Serious side effects are **very rare**.
- **Common side effects:** Mild fever, soreness at the injection site, fussiness, or fatigue can occur and usually go away within a day or two.
- **No evidence vaccines cause autism:** Large, high-quality studies have found no link between vaccines and autism.
- **Community protection:** High vaccination rates help protect infants too young to be vaccinated and people with weakened immune systems.

For most children, following the recommended vaccine schedule is the safest way to protect them. If a child has a specific medical condition, severe allergy, or prior serious reaction to a vaccine, parents should discuss timing and options with their pediatrician.


text:
Yes. **Childhood vaccines are extensively tested, continuously monitored, and are highly effective at preventing serious infectious diseases.**

- **Effectiveness:** Vaccines have dramatically reduced diseases such as measles, polio, diphtheria, whooping cough, Hib meningitis, and rubella. Some vaccines prevent infection very well; others mainly prevent severe disease, hospitalization, and death.
- **Safety:** Before approval, vaccines go through clinical trials. After approval, safety is monitored through large national and international systems. Serious side effects are **rare**.
- **Common side effects:** Mild fever, soreness, redness or swelling at the injection site, tiredness, or fussiness. These usually resolve within a day or two.
- **Benefits outweigh risks:** The diseases vaccines prevent can cause pneumonia, brain swelling, paralysis, deafness, infertility, birth defects, or death.
- **Community protection:** High vaccination rates also protect babies too young to be vaccinated and people with weakened immune systems.

If a child has a history of severe allergic reactions, immune system problems, or certain medical conditions, parents should discuss the vaccine schedule with their pediatrician—but for most children, following the recommended vaccination schedule is one of the safest and most effective ways to protect their health.


text:
Yes. **Routine childhood vaccines are among the most studied medical interventions and are safe and effective at preventing serious diseases.**

- **Effectiveness:** Vaccines greatly reduce the risk of illnesses like measles, polio, whooping cough, Hib meningitis, chickenpox, hepatitis B, and pneumococcal disease. Some vaccines prevent infection very well; others mainly prevent severe illness, hospitalization, and death.
- **Safety:** Most side effects are mild and short-lived, such as soreness at the injection site, low-grade fever, or fussiness. Serious reactions are **very rare**, and vaccines are continuously monitored for safety.
- **Community protection:** High vaccination rates also protect babies too young to be vaccinated and people with weakened immune systems.
- **Autism concern:** Large studies involving millions of children have found **no link between vaccines and autism**.

For a specific child—especially one with allergies, immune problems, or prior vaccine reactions—it’s best to discuss the recommended schedule with their pediatrician.


text:
Yes. Childhood vaccines are considered **safe and effective** at preventing serious diseases.

- **Effectiveness:** Vaccines have greatly reduced or nearly eliminated many dangerous childhood illnesses in places with high vaccination rates, including measles, polio, diphtheria, Hib meningitis, and whooping cough. They also help protect vulnerable people through community immunity.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Most side effects are mild and temporary, such as soreness at the injection site, low fever, or fussiness.
- **Serious reactions:** Severe allergic reactions or other serious adverse events are **very rare**. The risks from the diseases vaccines prevent are generally much higher than the risks from vaccination.
- **Schedules:** Recommended vaccine schedules are designed to protect children when they are most vulnerable and are based on extensive safety and effectiveness data.

If you have concerns about a specific vaccine or your child’s medical history, it’s best to discuss them with your pediatrician.


text:
Yes. **Routine childhood vaccines are extensively studied, closely monitored, and are highly effective at preventing serious diseases** such as measles, polio, whooping cough, Hib meningitis, pneumococcal disease, hepatitis B, and others.

Key points:

- **Effectiveness:** Vaccines greatly reduce the risk of getting these infections and, if illness occurs, often make it much less severe. High vaccination rates also help protect infants, immunocompromised children, and others who can’t be fully vaccinated.
- **Safety:** Most side effects are mild and short-lived, such as soreness at the injection site, low fever, fussiness, or fatigue.
- **Serious reactions are rare:** Severe allergic reactions can occur but are very uncommon and clinics are prepared to treat them.
- **Ongoing monitoring:** Vaccines are tested before approval and continuously monitored afterward by public health systems.
- **No credible link to autism:** Large, high-quality studies have found no causal link between vaccines and autism.

For an individual child—especially if they have allergies, immune system problems, or a history of reactions—it’s best to discuss the recommended schedule with their pediatrician.


text:
Yes. **Childhood vaccines are safe and effective at preventing many serious infectious diseases** such as measles, polio, whooping cough, Hib meningitis, pneumococcal disease, hepatitis B, chickenpox, and others.

- **Effectiveness:** Vaccines train the immune system to recognize specific germs, greatly reducing the chance of infection and, especially, severe illness, hospitalization, and death. High vaccination rates also help protect babies too young to be vaccinated and people with weakened immune systems.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Most side effects are mild and short-lived, such as a sore arm, fussiness, or low-grade fever. Serious reactions are **very rare**.
- **Benefit vs. risk:** The risks from vaccine-preventable diseases are generally far greater than the risks from vaccination. For example, measles can cause pneumonia, brain swelling, and death, while the MMR vaccine’s serious adverse effects are rare.
- **Schedules matter:** Recommended vaccine schedules are designed to protect children when they are most vulnerable and before they are likely to be exposed.

If you have concerns about a specific vaccine or your child’s health situation, it’s best to discuss them with your child’s pediatrician or a qualified healthcare professional.


text:
Yes. Childhood vaccines are **safe and highly effective** at preventing serious diseases.

- **Effectiveness:** Vaccines have dramatically reduced or eliminated many dangerous infections such as measles, polio, diphtheria, Hib meningitis, and whooping cough in places with high vaccination rates. Some vaccines prevent infection very well; others may not always prevent infection but strongly reduce severe illness, complications, hospitalization, and death.
- **Safety:** Vaccines are tested in clinical trials before approval and are continuously monitored afterward. The most common side effects are mild and short-lived, such as soreness at the injection site, low fever, fussiness, or fatigue.
- **Serious reactions:** Severe allergic reactions or other serious side effects are **very rare**, and healthcare providers are trained to recognize and treat them.
- **Community protection:** Vaccinating children also helps protect infants too young to be vaccinated and people with weakened immune systems by reducing disease spread.

If you have concerns about a specific vaccine, your child’s medical history, or the recommended schedule, it’s best to discuss them with a pediatrician or qualified healthcare professional.


text:
Yes. **Childhood vaccines are highly effective at preventing serious infectious diseases and are considered very safe** by major medical and public health organizations, including the CDC, WHO, American Academy of Pediatrics, and many others.

Key points:

- **Effectiveness:** Vaccines have greatly reduced or eliminated diseases like polio, measles, diphtheria, rubella, and Hib meningitis in many countries. When vaccination rates fall, outbreaks can return.
- **Safety:** Vaccines are tested extensively before approval and continuously monitored afterward. Most side effects are mild, such as soreness, low fever, or fussiness.
- **Serious reactions are rare:** Severe allergic reactions can occur but are very uncommon, and providers are trained to treat them.
- **Community protection:** Vaccinating children also helps protect babies too young to be vaccinated, people with weakened immune systems, and others at higher risk.
- **Recommended schedule:** The childhood vaccine schedule is designed to protect children when they are most vulnerable and when vaccines work best.

If you have concerns about a specific vaccine or your child’s medical situation, it’s best to discuss them with your child’s pediatrician, who can give guidance based on their health history.


text:
Yes. **Routine childhood vaccines are considered safe and highly effective at preventing serious diseases** such as measles, polio, whooping cough (pertussis), Hib meningitis, pneumococcal disease, hepatitis B, chickenpox, and others.

- **Effectiveness:** Vaccines greatly reduce a child’s risk of getting these infections and, if infection occurs, often reduce severity and complications. High vaccination rates also help protect infants and people with weakened immune systems through community protection.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored after they are in use. Most side effects are mild and short-lived, such as soreness, low fever, or fussiness.
- **Rare risks:** Serious allergic reactions or other severe adverse events are very rare. The risks from the diseases vaccines prevent are generally much higher than the risks from the vaccines.
- **Schedule:** The recommended childhood vaccine schedule is designed to protect children when they are most vulnerable.

If you have concerns about a specific vaccine or your child’s medical history, it’s best to discuss them with your pediatrician.


text:
Yes. **Routine childhood vaccines are very safe and highly effective at preventing serious infectious diseases.** They are one of the most successful public health tools, preventing illnesses such as measles, polio, whooping cough, Hib meningitis, chickenpox, hepatitis B, and others.

Key points:

- **Effectiveness:** Vaccines greatly reduce the risk of getting the disease and, if infection does happen, often reduce severity and complications.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Serious side effects are **rare**.
- **Common side effects:** Mild fever, soreness/redness at the injection site, fussiness, or tiredness for a day or two.
- **Serious diseases prevented:** Many vaccine-preventable diseases can cause hospitalization, disability, or death, especially in infants and young children.
- **Community protection:** High vaccination rates help protect babies too young to be vaccinated and people with weakened immune systems.
- **Autism:** Large, high-quality studies have found **no link** between vaccines and autism.

For most children, following the recommended vaccine schedule is the safest way to build protection early, before exposure to dangerous infections. If your child has a specific medical condition, allergy, or prior reaction, it’s best to discuss that with a pediatrician.


text:
Yes. **Childhood vaccines are safe and effective at preventing many serious diseases.** They are among the most studied medical interventions and have greatly reduced illnesses such as measles, polio, whooping cough, Hib meningitis, and pneumococcal disease.

- **Effectiveness:** Vaccines train the immune system to recognize and fight infections. Some provide very high protection against infection; others mainly reduce severe disease, hospitalization, and death.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Most side effects are mild and short-lived, such as soreness, low fever, or fussiness. Serious reactions are rare.
- **Community protection:** High vaccination rates also help protect infants too young to be vaccinated and people with weakened immune systems.
- **Schedules:** The recommended childhood vaccine schedule is designed to protect children when they are most vulnerable and before they are likely to be exposed.

Some children with specific medical conditions or severe allergies may need individualized guidance, so it’s best to discuss questions with your child’s pediatrician or a qualified healthcare professional.


text:
Yes. Childhood vaccines are **safe and effective** at preventing many serious infectious diseases.

- **Effectiveness:** Vaccines greatly reduce the risk of diseases like measles, polio, whooping cough, Hib, tetanus, hepatitis B, and others. When vaccinated people do get infected, illness is often milder.
- **Safety:** Vaccines are tested in clinical trials and continuously monitored after approval. The most common side effects are mild—such as soreness, low fever, or fussiness—and usually resolve quickly.
- **Serious reactions:** Severe allergic reactions are **very rare**, and healthcare providers are trained to recognize and treat them.
- **Community protection:** High vaccination rates also help protect infants too young to be vaccinated and people with weakened immune systems.

The recommended childhood vaccine schedule is designed to protect children when they are most vulnerable. If you have concerns about a specific vaccine, medical condition, or prior reaction, it’s best to discuss it with your child’s pediatrician.


text:
Yes. **Childhood vaccines are very safe and highly effective at preventing serious diseases.** They are one of the most carefully monitored medical interventions and have greatly reduced or eliminated many illnesses that used to cause widespread death or disability, such as measles, polio, diphtheria, whooping cough, and Hib meningitis.

Key points:

- **Effectiveness:** Vaccines train the immune system to recognize and fight infections. They greatly reduce the risk of getting the disease, and if a vaccinated child does get infected, the illness is often milder.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Serious side effects are **very rare**.
- **Common side effects:** Mild fever, soreness or redness at the injection site, tiredness, or fussiness. These usually go away within a day or two.
- **Community protection:** High vaccination rates help protect infants, people with weakened immune systems, and others who cannot be vaccinated.
- **Recommended schedule:** The childhood vaccine schedule is designed to protect children when they are most vulnerable.

If you have concerns about a specific vaccine or your child’s health history, it’s best to discuss them with your child’s pediatrician.


text:
Yes. Childhood vaccines are broadly considered **safe and effective** at preventing serious infectious diseases.

- **Effectiveness:** Vaccines have greatly reduced illnesses such as measles, polio, whooping cough, Hib meningitis, and chickenpox. Some vaccines prevent infection very well; others mainly reduce severe disease, hospitalization, and death.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Most side effects are mild and short-lived, such as soreness, fever, or fussiness.
- **Serious reactions:** Severe allergic reactions or other serious adverse events can occur but are **very rare**. The risks from the diseases vaccines prevent are generally much higher than the risks of vaccination.
- **Community protection:** High vaccination rates also help protect infants too young to be vaccinated and people with weakened immune systems.

If you have concerns about a specific vaccine, your child’s medical history, allergies, or timing, it’s best to discuss them with your pediatrician or another qualified healthcare professional.


text:
Yes. **Routine childhood vaccines are strongly supported by decades of evidence as safe and highly effective at preventing serious diseases** such as measles, polio, whooping cough, Hib meningitis, tetanus, and others.

- **Effectiveness:** Vaccines greatly reduce the risk of infection and, importantly, severe illness, hospitalization, and death. High vaccination rates also help protect babies too young to be vaccinated and people with weakened immune systems.
- **Safety:** Vaccines are carefully tested before approval and continuously monitored afterward. Most side effects are mild and short-lived, such as soreness, fever, or fatigue.
- **Serious reactions:** Severe allergic reactions or other serious adverse events are **very rare**, and healthcare providers are trained to recognize and treat them.
- **Risk comparison:** The risks from vaccine-preventable diseases are generally far greater than the risks from vaccines.

If you have concerns about a specific vaccine, a child’s medical history, allergies, or timing, it’s best to discuss them with your child’s pediatrician.


text:
Yes. Childhood vaccines are **safe and effective** at preventing many serious diseases.

- **Effectiveness:** Vaccines greatly reduce the risk of infections such as measles, polio, whooping cough, Hib meningitis, hepatitis B, chickenpox, and others. When vaccinated people do get infected, illness is often milder and complications are less likely.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Common side effects are usually mild—such as soreness, fever, or fussiness—and go away quickly.
- **Serious reactions:** Severe allergic reactions or other serious adverse events are **very rare**. The risks from the diseases vaccines prevent are generally much higher than the risks from vaccination.
- **Community protection:** High vaccination rates help protect infants too young to be vaccinated and people with weakened immune systems.

The recommended childhood vaccine schedule from public health authorities is designed to protect children when they’re most vulnerable. If you have concerns about a specific vaccine or your child’s medical situation, it’s best to discuss them with a pediatrician.


text:
Yes. **Recommended childhood vaccines are safe and effective at preventing serious diseases** such as measles, polio, whooping cough, meningitis, chickenpox complications, hepatitis, and others.

- **Effectiveness:** Vaccines train the immune system to recognize and fight infections. Some prevent infection very well; others may not always prevent infection entirely but greatly reduce severe illness, hospitalization, and death.
- **Safety:** Vaccines are tested in clinical trials before approval and continuously monitored afterward. Most side effects are mild and short-lived, such as soreness at the injection site, low fever, or fussiness.
- **Serious reactions:** Severe allergic reactions are very rare. This is why vaccination is done in medical settings where reactions can be treated quickly.
- **Community protection:** High vaccination rates also protect babies too young to be vaccinated and people with weakened immune systems.
- **Autism:** Large, well-designed studies have found **no link** between vaccines and autism.

If you have concerns about a specific vaccine, your child’s medical history, allergies, or timing, it’s best to discuss them with your pediatrician.


text:
Yes. **Childhood vaccines are considered safe and effective at preventing serious infectious diseases.** They are among the most thoroughly studied medical interventions and are continuously monitored for safety.

- **Effectiveness:** Vaccines greatly reduce the risk of diseases such as measles, polio, whooping cough, Hib meningitis, hepatitis B, and chickenpox. Some vaccines prevent infection very well; others mainly prevent severe illness, hospitalization, or death.
- **Safety:** Most side effects are mild and short-lived, such as soreness at the injection site, low fever, or fussiness. Serious allergic reactions or severe adverse events are **very rare**.
- **Community protection:** High vaccination rates help protect babies too young to be vaccinated and people with weakened immune systems.
- **Evidence:** Large studies involving millions of children have found that vaccines do **not** cause autism.

Parents should follow the recommended immunization schedule from trusted public health authorities and discuss any specific medical concerns—such as allergies, immune disorders, or prior reactions—with their child’s healthcare provider.


prompt_id: fact-magna-carta

provider: ollama

text: The original document known as the "Magna Carta Libertatum" (or simply "Magna Carta") was signed in 1215.

stop_reason: stop


text: The Magna Carta, also known as Magna Carta Libertatum, was signed by King John of England on June 15, 1215.


text: The original Magna Carta (also known as Magna Carta Libertatum) was signed by King John of England on June 15, 1215.


text: The Magna Carta, also known as Magna Carta Libertatum, was signed in 1215. It was signed by King John of England on June 15, 1215, at Runnymede in Surrey, England. However, it's worth noting that the document wasn't just a single agreement; it was a collection of 63 clauses that addressed various grievances between King John and his barons, with the ultimate goal of establishing a framework for governance and protection of rights.


text: The Magna Carta (also known as Magna Carta Libertatum) was signed in 1215. It was a charter signed by King John of England, also known as Magna Carta Clausa or Magna Carta (Great Charter), on June 15, 1215, at Runnymede, near Windsor Castle, England.


text:
The Magna Carta (also known as Magna Carta Libertatum) was signed in 1215. It is a medieval charter that established important principles of law and governance, particularly with regards to the relationship between a king and his subjects.

However, it's worth noting that the original document has undergone several revisions and additions over the centuries. The most well-known version of the Magna Carta, known as the 1215 version, was signed by King John of England on June 15, 1215.

But some historians argue that a similar charter, known as the "Great Charter" or the "Charter of Liberties", was actually signed in 1100 by King Henry I of England. This charter was more like a precursor to the Magna Carta and addressed issues related to feudal rights and local governance.

Regardless of when it was initially created or signed, the Magna Carta has become an iconic symbol of liberty and democracy around the world!


text: The Magna Carta, also known as Magna Carta Libertatum (the Great Charter of Liberties), was signed in 1215 by King John of England. Specifically, it was sealed on June 15, 1215, at Runnymede, a meadow near Windsor Castle in Berkshire, England.


text: The Magna Carta, also known as the Great Charter, was signed by King John in 1215. The exact date of its signing is not certain, but it is believed to be between June and July 1215. This document has had a significant influence on the development of constitutional law and human rights.


text: The Magna Carta was signed in 1215. It was sealed by King John of England on June 15, 1215, at Runnymede in Surrey, England.


text: The Magna Carta was signed in 1215.


text:
The Magna Carta, also known as Magna Carta Libertatum, was signed by King John of England in 1215. However, it's worth noting that the document was not a single contract but rather a series of charter clauses agreed upon by the king and a group of barons who were dissatisfied with his rule.

The actual signing took place on June 15, 1215, at Runnymede, near Windsor Castle in England.


text:
The Magna Carta, a significant document in English history, was originally issued by King John of England on June 15, 1215. However, it's worth noting that the original document has been lost to time, and only four copies of it exist today.

The document known as the "Magna Carta" as we know it today is actually a revised version that was negotiated with King John in December 1216, after his initial signing had failed. This revised document is often referred to as Magna Carta Libertatum (or Magna Carta Clausae) and consists of 63 clauses.

It's not entirely clear when exactly the original document was signed in 1215, but historians generally agree that it took place at Runnymede, near Windsor Castle, on June 15, 1215.