Over 1.5 million years ago, two distinct species of early humans, Homo erectus and Paranthropus boisei, walked side by side along the shores of an ancient lake in Kenya, leaving behind fossilized footprints. These extraordinary imprints offer a rare glimpse into a time when different human species may have coexisted, sharing a habitat rather than competing for territory.
The discovery was made during an excavation in July 2021 at Koobi Fora, located on the eastern shore of Lake Turkana, a site renowned for its rich collection of human ancestor fossils. Initially, a single hominin footprint was found alongside tracks left by large birds. Further excavation in 2022 uncovered a series of 12 hominin footprints in a straight line, suggesting they were made by the same individual. In addition, three isolated footprints, likely made by different individuals, were also found.
The tracks, preserved in soft mud, were left behind at a time when the area was part of a shallow delta system with low-energy water, ideal for preserving footprints. The researchers, unable to directly date the footprints, noted that they were located below a layer of volcanic ash known to be around 1.52 million years old. This, along with the pristine condition of the footprints, indicated that they were made within a short window of time—likely within a few hours or days.
The team determined that these footprints were likely made by two hominin species—Homo erectus and Paranthropus boisei—based on differences in the gait and foot anatomy visible in the tracks. Detailed analysis of the footprints, including 3D imaging, revealed that the 12-foot trackway was made by an individual whose footprints differed from those of modern humans, suggesting that it belonged to Homo erectus. Meanwhile, the other three scattered footprints, which closely resembled those of modern humans, were attributed to Paranthropus boisei, a species with a smaller brain and larger jaws adapted to a plant-based diet.
This discovery is groundbreaking because it provides the first physical evidence of two different hominin species overlapping in time and space. It suggests that instead of competing, these species may have coexisted peacefully in the same environment, likely avoiding direct competition for food and resources. The researchers speculated that the presence of dangerous wildlife, such as crocodiles and hippos, may have contributed to their need to repeatedly visit these areas over a prolonged period of time.
The footprints provide fascinating insight into the lives of these early humans and their ability to adapt to shared environments. Homo erectus, known for their more human-like anatomy, survived for over a million years after this encounter, while Paranthropus boisei went extinct within the next few hundred thousand years. The reasons behind this extinction remain unclear, but the coexistence of these species in the same landscape challenges our understanding of early human competition and survival.
This discovery also adds to growing evidence that different species of hominins, such as Neanderthals and Homo sapiens, not only coexisted but may have interbred, as genetic evidence has shown. The ancient landscape where these footprints were found may have been a place where early humans learned to navigate their environment, dodge predators, and share resources, providing us with a clearer picture of their everyday lives.
