About 120,000 years ago, some three dozen men, women, and children stepped across wet volcanic ash on the ancient shores of Lake Natron in Tanzania. By scrutinizing their well-preserved trail, researchers have gotten their first snapshot of what a traveling group of archaic humans looked like, down to the size of the group and the ratio of men to women with children, according to paleo-anthropologist Brian Richmond of George Washington University in Washington, D.C.
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