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These ancient footprints trample the old view, proposed in the 1950s by the evolutionary biologist Ernst Mayr, that no two hominin species overlapped in time and space, says William Harcourt-Smith, a paleoanthropologist at the American Museum of Natural History who wrote a commentary accompanying the new paper.

“I don’t think they should be a part of it at all because they are committing crimes against humanity,” said local resident Lorenzo Mayr, who attended a demonstration on Thursday.

The study was led by former lab member Ellen Horste, PhD, whom Mayr tapped for the daunting but exciting project when she joined the lab several years ago.

"When we started, we had a hard time getting funding for this project," Dr. Mayr says.

Two of the key components at the heart of the Mayr team's study don't have membranes -- which is what has made them so hard to find in the first place, and a challenge to isolate and study in the lab.