Two species of human ancestors literally crossed paths 1.5 million years ago

Once upon a time, more than a million years ago, the hot savannah near what we now know as Lake Turkana in Kenya served as a bustling hub, where two completely distinct species of hominins left their footprints in history.

Recent discoveries reveal that these two species, engrossed in their search for sustenance, might have unknowingly crossed paths and left a tangible mark on our understanding of human evolution.

Mystery of hominin footprints

Hominin is the term used to group species that branched off the evolutionary tree after the ancestors of the great apes diverged, about 6-7 million years ago.

The Hominins thus include all the species that were directly ancestral to humans or were closely related to them.

The fascinating discovery of 1.5-million-year-old footprints is like peering through a window into our past.

According to scientists, this is the first discovery of fossilized tracks where two different species of hominin left their footprints concurrently on the same ancient lake shore.

This finding could help us to understand how hominin species interacted with and affected each other.

A breakthrough discovery

A recent publication in the journal Science presents irrefutable evidence of different hominin species co-existing in the same space and temporal frame.

The footprints imprinted by individuals of the species Homo erectus and Paranthropus boisei, which are two of the most common hominin species of the Pleistocene Epoch, narrate the story of their lives.

“Their presence on the same surface, made closely together in time, places the two species at the lake margin, using the same habitat,” said Craig Feibel, an author of the study and a professor in the Department of Earth and Planetary Sciences and Department of Anthropology in the Rutgers School of Arts and Sciences.

Tracking hominin footprints

Feibel, along with researchers led by Cyprian Nyete, discovered the footprints in 2021. A surprise awaited them as they unearthed not just giant bird tracks but hominin footprints as well.

The footprints told an intriguing story. If the two species of hominins didn’t cross paths, they tread the shore within hours of each other, according to Feibel.

“Fossil footprints are exciting because they provide vivid snapshots that bring our fossil relatives to life,” said Kevin Hatala, the study’s first author and an associate professor of biology at Chatham University in Pittsburgh.

“With these kinds of data, we can see how living individuals, millions of years ago, were moving around their environments and potentially interacting with each other, or even with other animals. That’s something that we can’t really get from bones or stone tools,” he added.

Co-existence of two hominin species

The discovery of hominin footprints is, as Feibel puts it, “a bit of serendipity.” The findings demonstrate the co-existence of these species and supports a hypothesis that has been around for a while.

According to fossil records, Homo erectus, our direct ancestor, persisted for a million years more than Paranthropus boisei. The reasons behind the extinction of Paranthropus boisei remain unknown.

Transcending the physical evidence

The footprints acquire a significant position in the study of human evolution. In Feibel’s words, they fall into the category of “trace fossils,” that provide non-physical evidence of behavior.

Unlike body fossils (such as bones and teeth) that can be moved by natural forces, trace fossils remain untouched, preserving an authentic record of past behaviors.

The discovery of these footprints opens a gateway into the past by showing directly that distinct kinds of human relatives co-inhabited the same place at the same time.

Even more intriguing is the possibility that the two groups might have interacted, influencing each other in ways we are yet to fully comprehend.

Insights from ancient hominin footprints

The study of these ancient footprints offers valuable insights into the behavior and movement patterns of our prehistoric ancestors.

By examining the size, shape, and stride length of the footprints, researchers can gather information about the individuals’ walking speed, body proportions, and possibly even their social dynamics.

This invaluable evidence provides a window into the daily lives and interactions of Homo erectus and Paranthropus boisei, shedding light on our shared history and the complexities of our evolutionary journey.

Understanding human evolution

The coexistence and potential interaction between Homo erectus and Paranthropus boisei have significant implications for our understanding of human evolution.

It challenges the linear narrative of human evolution and highlights the complexity and diversity of our evolutionary past.

The presence of multiple species in the same environment suggests that different hominin groups may have occupied distinct ecological niches and developed unique adaptations.

By studying these ancient footprints, we not only unravel the story of our ancestors but also gain a deeper appreciation for the intricate tapestry of human evolution.

The journey of our prehistoric ancestors

The footprints of Homo erectus and Paranthropus boisei provide a tangible narrative of our prehistoric ancestors. They reveal how distinct paths paved the way for our evolution.

“This proves beyond any question that not only one, but two different hominins were walking on the same surface, literally within hours of each other,” Feibel said.

“The idea that they lived contemporaneously may not be a surprise. But this is the first time demonstrating it. I think that’s really huge.”

The study is published in the journal Science.

Image Credit: Kevin Hatala/Chatham University

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