The Jordan Harbinger Show

1272: Left-Handedness | Skeptical Sunday

35 snips
Jan 18, 2026
Guest
Jessica Wynn
Jessica Wynn, a writer and researcher specializing in science communication, dives into the intriguing world of left-handedness. She reveals that being a lefty isn't just about genetics; it's a mix of prenatal factors and chance. Fascinatingly, ultrasound studies show fetuses exhibit hand preferences early on. Wynn also discusses the brain's wiring in left-handers, leading to enhanced multitasking and creativity. Cultural taboos and historical biases against lefties are explored, shedding light on the unique challenges they face in a right-handed world.
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INSIGHT

Handedness Is Multifactorial

  • Handedness arises from a mix of genetics, prenatal environment, and random brain development.
  • No single gene controls it; small genetic effects plus fetal position and hormones nudge lateralization early on.
INSIGHT

TUBB4B Variant Is Correlated, Not Causal

  • The rare TUBB4B gene variant appears more often in left-handers but doesn't fully explain left-handedness.
  • Identical twins can differ in handedness, showing genes alone aren't determinative.
INSIGHT

Womb Behavior Predicts Dominant Hand

  • Fetal behavior predicts later handedness: consistent thumb-sucking and head-turn bias show up by ~18 weeks.
  • Position and sensory feedback in utero reinforce which side the brain favors long before birth.
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