Study of 87 Hominin Skulls Finds Brain Growth Was Neutral, Not Selection-Driven
Updated
Updated · New Scientist · Jul 3
Study of 87 Hominin Skulls Finds Brain Growth Was Neutral, Not Selection-Driven
3 articles · Updated · New Scientist · Jul 3
Summary
A new analysis of 87 hominin skulls found the rise in human brain size over the past 2 million years is best explained by neutral evolution rather than strong natural selection.
Mathematical tests of six evolutionary scenarios showed braincase changes accumulated largely through random mutations, alongside periods of stasis when evolution constrained brain size and shape.
Facial anatomy followed a similar pattern—faces became flatter and less protruding over time—but the stabilizing pressure on facial form appeared stronger than for braincases.
Researchers and outside experts said skull data capture only overall brain size and shape, not internal reorganization; one critic also said the fossil sample remains too small for firm conclusions.
Harvati suggested larger brains may have emerged when biological constraints eased, with calorie-rich cooked food as one possible factor that helped support the brain's high energy demands.