EconTalk

Nature, Nurture, and Identical Twins (with David Bessis)

75 snips
Jan 19, 2026
In this engaging discussion, mathematician and author David Bessis challenges the narrative of genetic determinism in the context of identical twins raised apart. He critiques famous studies that claim high heritability in traits like IQ, emphasizing flaws and biases in the data. Bessis introduces Eric Turkheimer's laws, illustrating the significant role of unique experiences in shaping individuals. The conversation explores the limitations of twin studies and underscores how personal journeys, rather than genetics alone, heavily influence talent and abilities.
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INSIGHT

Twin Studies Are Not Definitive Proof

  • David Bessis argues that famous twins-reared-apart studies are not definitive evidence that genetics fully determine IQ.
  • He shows the “perfect experiment” doesn’t exist in real life and the literature has many flaws.
ANECDOTE

Bill Thurston’s Unique Developmental Journey

  • Bessis recounts Bill Thurston's childhood, where a mother’s sustained training overcame a visual defect.
  • That unique journey helped Thurston develop world-class geometric ability and become a mathematical genius.
INSIGHT

Heritability Percentages Don’t Tell The Whole Story

  • A 30–80% heritability number leaves wide room for non-genetic influences and ambiguity in meaning.
  • Even 50% heritability still allows many individuals with average genes to reach high achievement.
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