Finger Length and Brain Evolution | Science News

Science News Today | 2 Min News | The Daily News Now! · Jul 17, 2026 · 1m

Scientists discovered a surprising link between baby finger ratios and brain size: boys with longer index fingers (higher 2D:4D ratio, indicating higher prenatal estrogen) tended to have bigger head circumferences—suggesting estrogen may have fueled human brain evolution. This finding supports the “estrogenized ape” theory, proposing that hormonal shifts during human evolution helped shrink our skeletons while expanding our brains. The effect was exclusive to males, hinting at a biological trade-off that may have propelled our cognitive leap. Listen in comfort:Get a discount on a Soli Pillow…