The oldest known fossil skeleton of a human ancestor–a female Ardipithecus ramidus specimen nicknamed “Ardi” (pictured)–has been found, scientists revealed yesterday.

The find reveals that our ancestors underwent a previously unknown stage of evolution more than a million years before Lucy, the early human ancestor specimen that walked the Earth 3.2 million years ago. Ardi lived 4.4 million years ago, according to researchers.

See more pictures, a map, and read a report of the discovery on National Geographic News.

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