There’s plenty of evidence that ancient hominin species crossed paths on many occasions – but it’s never been quite as literal as a new discovery in Kenya. Paleontologists have discovered the first known example of fossil footprints left by two different species of ancient hominins on the same day.

About 1.5 million years ago, individuals of two different species in the human evolutionary lineage trudged on a muddy lakeshore in northern Kenya, leaving behind intersecting trackways alongside the footprints of antelopes,

The footprints were left in the mud by two different species “within a matter of hours, or at most days,” a co-author of the research study said.