Twin and adoption studies estimate genetic contribution to intelligence at 50–70% heritability, though molecular GWAS estimates run lower.

Evidence

Twin Studies and the Heritability of IQ (Aporia Magazine)

Categorization

• corroborated: 2 independent passages support this claim
• XREF: connects to: Intelligence is malleable and shaped by environment, not fixed by heredity — Harriet A. Washington, A Terrible Thing to Waste, 54; With heritability well below 1.00, IQ must be subject to substantial environmental influences, though genetic influence increases with age while shared family environment effects shrink by late adolescence. — Intelligence: Knowns and Unknowns; Intelligence develops from environment and experience rather than genetic inheritance (+4 more)

Related

• MZ twins correlate at ~.85 for IQ versus .55 for DZ twins, giving heritability estimates of 50–80% in adults, with heritability rising from childhood to adulthood. (similarity 0.90)
• With heritability well below 1.00, IQ must be subject to substantial environmental influences, though genetic influence increases with age while shared family environment effects shrink by late… (similarity 0.88)
• Large positive and negative trends in cohort IQ operate within as well as across families, implying at most a minor role for genes, with environment as the main driver. (similarity 0.87)
• With heritability well below 1.00, IQ must be subject to substantial environmental influences, though genetic influence increases with age while shared family environment effects shrink by late adolescence. (similarity 0.85)
• Intelligence develops from environment and experience rather than genetic inheritance (similarity 0.84)
• Genetic causation of a trait does not imply the trait is unchangeable (similarity 0.83)
• Twin studies attribute about seventy percent of intelligence variance to genetics (similarity 0.82)
• Intelligence is malleable and shaped by environment, not fixed by heredity (similarity 0.82)
• Shared home environment has almost no effect on intelligence variance. (similarity 0.81)
• High heritability of individual differences and large environmental effects on population-level IQ are mathematically compatible under a reciprocal gene-environment coupling model (Dickens & Flynn). (similarity 0.81)
• Mixed-race children’s IQ tracks rearing environment, not racial genetics (similarity 0.79)
• IQ’s link to income mostly reflects environment’s link to both (similarity 0.79)

Library Connections

• Rapid IQ gains from reduced disease burden rule out genetic explanations #contradicts (0.90) — Harriet A. Washington, A Terrible Thing to Waste, 945