Footprints discovered in 1978 at in Tanzania and dated to 3.66 million years ago were widely thought to be the oldest uncontested evidence of upright walking in the human family tree.

24 wild polar bear tracks and 44 wild lynx tracks were sampled. The researchers melted and filtered the snow to collect environmental DNA, then carried out microsatellite analysis.

WASHINGTON — Prehistoric footprints that have puzzled scientists since the 1970s are getting a second look: Were they left by extinct animals or by human ancestors?

A look at Africa's largest fossil footprint site 02:37. Prehistoric footprints that have puzzled scientists since the 1970s are getting a second look: Were they left by extinct animals or by human ...

The early humans who walked the earth nearly 3.7 million years ago were not walking alone. Fossil footprints in Tanzania reveal that two human species once lived in the same place at the same time.

Prehistoric footprints that have puzzled scientists since the 1970s are getting a second look — were they from extinct animals or humans?

On the left, a nearly 3.7 million year old fossil footprint now believed to have been made by an early human. On the right, the rear footprint of a young black bear.

Prehistoric footprints that have puzzled scientists since the 1970s are getting a second look: Were they left by extinct animals or by human ancestors?

A new look at nearly 3.7 million-year-old fossil footprints uncovered in Tanzania shows that multiple species of early humans lived together at the same time.

The early humans who walked the earth nearly 3.7 million years ago were not walking alone. Fossil footprints in Tanzania reveal that two human species once lived in the same place at the same time.