Last November, an international team of archaeologists discovered 1.5 million year old fossilised footprints of Homo erectus and Paranthropus boisei in Kenya’s Turkana Basin. While previous studies suggested that ancient hominin species lived in parts of Africa at the same time, definitive evidence of coexistence had been lacking – until now.
As Andy Herries of La Trobe University and the University of Johannesburg explains, “The dating resolution of these fossils [is] often impossible to say [if] they were there at exactly the same time.” The footprints, unearthed at the archaeological site of Koobi Fora in Northern Kenya, provide evidence that these two species in the Pleistocene epoch were “probably aware of each other’s existence,” and may have even interacted, according to Associate Professor Kevin Hatala, a paleoanthropologist at Chatham’s University, and lead author of the groundbreaking study, which was published in Science.
Another important finding from this study is our understanding of how ancient humans evolved to walk upright, called bipedalism. Unlike skeletal remains, which suggest upright walking, these footprints provide direct evidence of when and how species walked. The analysis of the footprints shows that both species were bipedal, though their walking styles differed significantly. Homo erectus, a direct ancestor to modern humans, was an efficient walker; in contrast, Paranthropus boisei, a more distant relative, exhibited a more robust structure and gait, reflecting its unique evolutionary path.
The discovery raises new questions about how these two species coexisted in the same environment. Neil Roach pondered, “Did this overlap increase competition between them for the same resources? Were they there for different purposes?” Despite significant differences in their anatomy, behaviour, and land use, both hominins were drawn to the vital resources provided by lakeshore environments. Professor Herries added that Paranthropus boisei was “an ultra-dietary specialist that ate tough foods,” reducing the likelihood of significant dietary overlap. These findings suggest that dietary specialisation and differing ecological roles likely minimized conflict, allowing the two species to share the same landscapes for 200,000 years.
However, their coexistence may have been disrupted by shifting climates, which likely altered resource availability. These environmental changes, including fluctuating water levels and vegetation shifts, would have intensified competition for diminishing resources, placing strain on less adaptable species. Professor Hatala explained that these environmental pressures likely “led to the extinction of Paranthropus boisei and the persistence of Homo erectus.”
The discovery of fossilised hominin footprints offers insights into the behavioural ecology of early hominins, offering new perspectives on competition and coexistence. As scientists continue to analyse these footprints and search for new evidence, we can expect further revelations in understanding our ancient ancestors – and the story of human evolution.