### Ancient Human Footprints Reveal Unexpected Coexistence of Two Species

In a remarkable archeological find, scientists have uncovered fossilized footprints that suggest two different species of early humans coexisted peacefully more than 1.5 million years ago on the shores of Lake Turkana in Kenya. This exceptional discovery challenges previous assumptions that ancient humans were strictly territorial and competitive.

During an excavation at Koobi Fora in July 2021, a team of researchers led by Kevin Hatala, an associate professor of biology at Chatham University, found an intriguing hominin footprint amidst tracks made by large birds. The site was carefully reburied with fine sand for a more detailed exploration in 2022. When the team returned, they revealed 23 square meters of sediment which exposed 11 additional hominin tracks aligned in a line that suggested they belonged to the same individual. The researchers also discovered three isolated footprints oriented perpendicularly, likely left by different individuals.

Alongside these human footprints, the team cataloged 94 nonhuman tracks, including those made by birds and animals resembling cows and horses. One particularly large bird track measuring 27 centimeters across was identified as belonging to a species of giant stork known as Leptoptilos.

Through meticulous 3D imaging and analysis, Hatala's team concluded that the long trackway was made by Paranthropus boisei, a smaller-brained hominin, while the three isolated footprints were likely created by Homo erectus. The conclusion was drawn based on the differences in gait, stance, and motion observed in the footprints, compared to the walking patterns of modern humans and other fossilized hominin prints.

Using experimental data from living humans, specifically 59 Daasanach people from Ethiopia who typically eschew footwear, and comparing these with other hominin prints and tracks made by chimpanzees, researchers validated their findings. They noted that Homo erectus shared many physical similarities with modern humans, suggesting that they were perhaps direct ancestors.

Interestingly, the footprints lie below a layer of volcanic ash known as Elomaling'a Tuff, dated at 1.52 million years old, positioning the tracks as even older. The researchers are certain the footprints were made within hours to a few days of each other, given their pristine preservation without surface cracking.

The coexistence of these two species implies they shared the same habitat without significant conflict, enduring the same environmental challenges and dangers from predators like hippos and crocodiles. Hatala and his colleagues believe this indicates low levels of direct competition between the species, allowing them to thrive side by side for perhaps up to 100,000 years. Nonetheless, while Homo erectus endured for another million years, Paranthropus boisei disappeared within a few hundred thousand years for reasons that remain unknown.

Briana Pobiner, a research scientist at the Smithsonian National Museum of Natural History’s Human Origins Program, referred to this dual-species discovery as "mind-blowing," given that it provided direct evidence of two species crossing paths in the same time and space. This finding opens up new questions about possible interactions and relationships between ancient human species, adding another layer to our understanding of human evolution.