How did humans evolve, and where did they migrate?

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Fossil Footprints from Laetoli in TanzaniaAbout 3.5 million years ago, several australopithecines walked in wet ash from a volcanic eruption. Their footprints, discovered by the archaeologist Mary Leakey, indicate that they walked fully upright and suggest that they were not solitary creatures, for they walked close together. (John Reader/Science Source)

SSTUDYING THE EARLIEST ERA OF HUMAN HISTORY involves methods that seem simple — looking carefully at an object — as well as new high-tech procedures, such as DNA analysis. Through such research, scholars have examined early human evolution, traced the expansion of the human brain, and studied migration out of Africa and across the planet. Combined with spoken language, that larger brain enabled humans to adapt to many different environments and to be flexible in their responses to new challenges.