Humans' tendency toward long childhoods may have evolved earlier than previously thought, a new study found, potentially even predating our large brain sizes. The study challenges the prevailing hypothesis the two evolved simultaneously.
The study, published yesterday in Nature, centers on the 1.8-million-year-old fossil of a roughly 11-year-old child discovered in Dmanisi, Georgia. Researchers studied X-rays of the child's molar teeth to identify stress lines and nutritional patterns, which they used to create a visual timeline of the child's dental development (see video).
The study suggests the child experienced slow early dental growth, relying on milk teeth for the first five years of life. Because the child belonged to a Homo species with only slightly larger brains than modern chimpanzees, the authors say long childhoods—in which humans rely on parents, grandparents, and other adults for support—may have predated humans' ability to grow larger brains.
Learn about long childhoods and the human brain here (w/video).
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