WE have our broad-hipped ancestors to thank for our big brains. The capacious birth canal of a newly unearthed Homo erectus fossil shows we evolved to accommodate a bulging brain as long as 1.2 million years ago.
鈥淏rain size is driving the whole system here,鈥� says Scott Simpson of Case Western Reserve University in Cleveland, Ohio, who was part of the team that uncovered the nearly complete fossil. 鈥淭he most successful individuals in these populations will have positive selection for [big] brains and large pelvises.鈥�
The new fossil offers a glimpse into the female influences on evolution, say the researchers, and might shatter the belief that H. erectus were marathon runners who hunted by exhausting their prey. The fossil shows few adaptations that would favour runners, such as a tall stature and a narrow pelvis (Science, ).
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