Two species of early humans were neighbours 1.5 mn years ago

Indicate muddy footprints left on a Kenyan lakeside by 2 different species 'within matter of hours, or at most days'

Muddy footprints left on a Kenyan lakeside suggest two of our early human ancestors were nearby neighbors some 1.5 million years ago.

The footprints were left in the mud by two different species "within a matter of hours, or at most days," said paleontologist Louise Leakey, co-author of the research published Thursday in the journal Science.

Scientists previously knew from fossil remains that these two extinct branches of the human evolutionary tree - called Homo erectus and Paranthropus boisei - lived about the same time in the Turkana Basin.

But dating fossils is not exact.

"It's plus or minus a few thousand years," said paleontologist William Harcourt-Smith of Lehman College and the American Museum of Natural History in New York, who was not involved in the study.