An anthropologist finds a fossil that is 4 million years old. Its pelvis suggests it walked upright. Which species could the specimen belong to?

Australopithecus afarensis lived about 3.9 to 2.9 million years ago and walked upright, as shown by its skeletal features. A fossil dated to 4 million years ago could therefore belong to this species. The other choices are generally associated with later periods.

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