By Ann GibbonsIn 1974, the world was stunned by the discovery of “Lucy,” the partial skeleton of a human ancestor that walked upright—and still spent time in the trees—3.2 million years ago.
Later discoveries revealed her species, scattered throughout eastern Africa, had brains bigger than chimpanzees. But a new study of an ancient toddler finds that the brains of Lucy’s kind were organized less like those of humans and more like those of chimps.
That suggests the brains of our ancestors expanded before they reorganized in the ways that let us engage in more complex mental behaviors such as making tools and developing language.
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