A new analysis of a set of 1.4-million-year-old fossilized footprints found along the shore of an ancient Kenyan lake revealed that the hominins responsible for leaving them were much larger than previously believed, with some specimens approaching the height and body size of modern humans.
The new analysis also determined that discovering a group of footprints belonging to eight different adult males from distant human ‘cousin’ species Paranthropus boisei walking together suggests a complex societal dynamic where males likely competed for females but also worked together for the group’s benefit.
1.4-Million-Year-Old Fossilized Footprints Reveal Unexpectedly Large Body Size
According to a statement announcing the new fossilized footprint analysis, the team behind the research had previously “pioneered” methods allowing science to accurately identify the footprints as belonging to Paranthropus boisei in 2024.
However, lead author Kevin Hatala, of Chatham University and an associated researcher of the Department of Human Origins at the Max Planck Institute for Evolutionary Anthropology in Leipzig, said the new approach, which analyzes foot anatomy and movement patterns based on the fossilized footprints, revealed much larger individuals than expected.
“The sizes of the footprints indicate human-like body sizes – up to 1.8 meters tall and around 75 kilograms”, Hatala said, noting that scientists studying the rare fossils available for Paranthropus boisei had previously assumed the species was much smaller than the modern human ancestor and contemporary hominin, Homo erectus.
For example, the researchers explain, the “overwhelming majority” of previously identified Paranthropus boisei fossils were skulls with massive jaws and teeth. However, they add, little is known about this ancient hominin’s anatomy from the neck down.
“A Window into Hominin Behavior and Group Dynamics”
Although indirect evidence compared to actual bones, the team notes that fossilized footprints form “very quickly.” This rapid formation helps preserve critical movement and anatomy data that the team notes “can be a useful window into hominin behavior and group dynamics.”
“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”, explained study co-author Neil Roach of Harvard University.
For example, Roach said the ancient footprint makers may have lived in large groups, “where males competed for mates.” However, he notes, the same footprints suggest these competing males “also tolerated each other at times for safety in a dangerous environment.”
“This discovery adds an important behavioral dimension to the fossil record of Paranthropus boisei, a species that lived alongside early members of the genus Homo, yet took a different evolutionary path,” they explain.
Proximity and Environmental Conditions Could Offer More Behavioral Clues
Although the study focused on the 1.4-million-year-old footprints found on the shore of an ancient Kenyan lake, the work joins a growing catalog of ancient hominin footprints left on equally ancient lake shores. To date, the team has documented hundreds of hominin footprints across more than a half-dozen sites in the local region.
When discussing the significance of their findings, the team noted that these 1.4-million-year-old footprints join this larger group in supporting ancient lakes as an “important habitat with critical resources” that our now-extinct relatives relied on for survival. Study co-author Kay Behrensmeyer of the Smithsonian Institution also highlighted the unexpected nature of the discovery of ancient footprint fossils so close to others from a similarly ancient 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”, the researcher explained.
Study co-author Anna K. Behrensmeyer from the Department of Paleobiology and Human Origins Program, National Museum of Natural History, Smithsonian Institution, said understanding the environment and local conditions when the footprints were left could fill in even more missing pieces about this enigmatic ancient hominin.
“If we can understand what geological conditions allowed these tracks to be preserved, we should know more about why hominins continued to return to the lake shore environment over more than 100,000 years,” Behrensmeyer said.
Building a Photo Album of Our Past
When detailing the significance of the new analysis, study co-author Purity Kiura of the National Museums of Kenya said finding these fossilized prints 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.”
“It further strengthens Kenya’s position as one of the world’s leading paleoanthropological landscapes and highlights our responsibility to protect this irreplaceable heritage,” Kiura added.
From a methodology standpoint, the team noted the benefit of combining new analytical approaches with “exceptional” fossil footprints. They also point out that ancient tracks like the 1.4 million-year-old footprints found in Kenya “can reveal the anatomy and movement of extinct human relatives, while also providing rare insights into their social lives and environments.”
To follow up on their findings, the research team said they plan to return to Kenya later this year and conduct more analysis of the footprints. According to Hatala, this work will help archaeologists and anthropologists fill in missing pieces of hominin history, especially those extinct branches of the evolutionary tree.
“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,” the researcher explained.
The study “Insights into hominin body size, locomotion, and behavior from Early Pleistocene trackways in northern Kenya” was published in the Proceedings of the National Academy of Sciences.
Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org