Human Evolution Rewritten: Breaks and Culture Behind Big Brains and Small Faces
A study of 87 fossil skulls from Homo habilis to Homo sapiens finds that larger brains and smaller faces did not arise from a steady, directional natural-selection path. Instead, evolution shows long periods of little change (stasis) with major shifts occurring when biological, environmental, or cultural barriers eased, aided by cultural innovations that supported energy-rich diets and technology. The findings, published in Nature Communications, imply modern anatomy reflects a combination of neutral drift, stabilizing selection, and episodic change rather than a simple linear march toward greater encephalization.