1.4-Million-Year-Old Footprints Reveal a Surprisingly Large Hominin
Bones can pile up over thousands of years, blurring together into an average. Footprints can’t. A single trackway freezes one specific moment, and a set of them just found in northern Kenya has frozen something remarkable: eight individuals of an extinct human relative, walking together, and standing taller than anyone expected.
A Snapshot of ‘Fossil Behavior’
A new study documents a set of fossil footprints preserving what researchers call a snapshot of “fossil behavior” from an ancient hominin group along a lakeshore in northern Kenya, dating to roughly 1.4 million years ago. An international team from the United States and Kenya found tracks showing eight Paranthropus boisei individuals, an extinct evolutionary cousin of modern humans, occupying the same place at the same time. The findings were published in the Proceedings of the National Academy of Sciences, led by Kevin Hatala of Chatham University, an associated researcher in the Department of Human Origins at the Max Planck Institute for Evolutionary Anthropology in Leipzig.
All eight individuals appear to have been adults, and several were considerably larger than previous estimates of Paranthropus boisei body size, which had been based almost entirely on rare and fragmentary skeletal remains.
A Human-Sized Surprise
The research team applied analytical methods it had pioneered in 2024 to identify the tracks as belonging to Paranthropus boisei, based on foot anatomy and the way the individuals appear to have moved. What the analysis revealed about their size came as a genuine surprise. “The sizes of the footprints indicate human-like body sizes, up to 1.8 meters tall and around 75 kilograms,” Hatala said.
For decades, the overwhelming majority of Paranthropus boisei fossils recovered by researchers have been skulls, some bearing exceptionally massive jaws and teeth. Far less has been known about the species below the neck, since fossils from the rest of the skeleton are considerably rarer. The new footprint evidence directly challenges earlier research suggesting Paranthropus boisei was substantially smaller-bodied than Homo erectus, a contemporary hominin and possible direct ancestor of modern humans.
A Group Without Females or Children
Because a footprint-bearing surface can form and get buried within a very short window of time, fossil trackways offer researchers something skeletal remains generally can’t: direct evidence of movement, group size, and social behavior captured in a single moment rather than averaged across generations.
In this case, the eight individuals appear to have been traveling together, and most were likely adult males, with no obvious evidence of females or children among them. “The fact that eight, mostly adult male, Paranthropus boisei individuals seemingly traveled together as a group, without females or children, hints at a complex social structure in this species,” said co-author Neil Roach of Harvard University. “They may have lived in large groups, where males competed for mates, but also tolerated each other at times for safety in a dangerous environment.”
That possibility adds a genuinely new dimension to scientific understanding of Paranthropus boisei, a species that shared its world with early members of the genus Homo yet followed an entirely separate evolutionary path, one that ultimately ended in extinction rather than survival.
Why the Lakeshore Kept Drawing Them Back
This latest discovery is part of a much larger and growing collection of hominin footprints recovered from ancient lakeshore environments around Lake Turkana, a pattern suggesting these margins offered resources valuable enough that different hominin groups returned to them again and again over an extraordinarily long stretch of time.
“To me, it is amazing that we have the same kind of lake margin deposits in two areas of East Turkana that are 40 kilometers apart, at about the same age,” said co-author Kay Behrensmeyer of the Smithsonian Institution. Researchers have now documented hundreds of hominin footprints across more than half a dozen sites throughout the region. Behrensmeyer suggests that understanding exactly what geological conditions allowed these fragile tracks to survive at all could, in turn, help explain why hominins kept returning to this same lakeshore environment for more than 100,000 years.
A Growing Photo Album of the Past
The research team plans to return to Kenya this year to continue investigating these footprint sites. “Each site represents a snapshot of our past, and we are quickly building a photo album with several different windows to hominin anatomy, locomotion, behavior, and environments during the Early Pleistocene,” Hatala said.
Co-author Purity Kiura of the National Museums of Kenya framed the discovery within a wider sense of scientific responsibility. “The discovery of these fossil footprints along the margins of Lake Turkana reinforces the region’s global importance in understanding human evolution, preserving remarkable evidence of how our ancient relatives lived 1.4 million years ago,” Kiura said. “It further strengthens Kenya’s position as one of the world’s leading paleoanthropological landscapes and highlights our responsibility to protect this irreplaceable heritage.”
By combining newly developed analytical techniques with an unusually well-preserved set of footprint sites, the study demonstrates just how much ancient tracks can reveal about extinct hominins that bones alone typically cannot, not just how they were built, but how they moved, where they spent their time, and quite possibly how they interacted with one another.
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