December 15, 2016 12:47 PM EST

Newly discovered footprints of five human ancestors that roamed the Earth 3.66 million years ago suggest that members of the Australopithecus afarensis species may have kept multiple mates at the same time, according to new research.

The new footprints, published in the journal e-Life, were discovered in Tanzania accidentally while a site was being considered for a proposed museum. The footprints were made in a layer of ash and preserved like clay.

Scientists evaluated the footprints and found that the group likely included one adult male, three adult females and a child, the latest evidence that the species was polygamous.

The newly discovered footprints are about the same age as the famous Lucy skeleton, also a member of the Australopithecus afarensis species.

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Write to Justin Worland at justin.worland@time.com.

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