New research led by University of the Witwatersrand and University of Southern California paleoanthropologists sheds more light on one of the most debated transitions in human evolution: when our ancestors stopped regularly climbing trees and committed fully to walking on two legs.
A set of 1.43-million-year-old fossil footprints preserved along the margin of an ancient lake in northern Kenya is offering paleoanthropologists new evidence about the size, gait and social lives of the beings who made them and reopening questions about which species they belonged to.
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.
One of the large, 1.4-million-year-old footprints that the team excavated. A 6-inch (~15 cm) ruler is shown for scale. Image Credit: Kay Behrensmeyer.
“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.
Approximately 1.43-million-year-old hominin footprint from Koobi Fora, Kenya. Image Credit: Kevin G. Hatala.
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.
Kevin Hatala and colleagues discuss the ancient footprints excavated in northern Kenya in 2023. Image Credit: Kay Behrensmeyer.
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.
Most Paranthropus boisei fossils are skulls. By Matt Celeskey from Albuquerque – Australopithecus boisei, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=32845963
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.
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
Homo erectus may have left a detectable genetic trace in living humans through ancient interbreeding with Denisovans. For much of the 20th century, human evolution was often pictured as a branching tree. One trunk split into separate limbs, and each ancient human relative, or hominin, occupied its own tidy branch. That was the version many [...]
Until about 60,000 years ago, diminutive hominin cousins, Homo floresiensis (affectionately nicknamed Hobbits for obvious reasons), shared the island of Flores with Komodo dragons, pygmy elephants, and giant rats.
Based on the presence of hominin and pygmy elephant bones in the same layers of cave sediment, it originally looked like the Hobbits had hunted and butchered dwarf elephants—an impressive feat for such a tiny hominin. But according to University of Tübingen anthropologist Elizabeth Veatch and her colleagues, it was the Komodo dragons that were the hunters, while the Hobbits only showed up to scavenge what was left.
If Veatch and her colleagues are right, their findings may challenge some of the assumptions we’ve made about Homo floresiensis—and about which hominin species was the first to venture into the wider world beyond Africa.
Scientists have uncovered compelling new evidence that early human ancestors, likely Homo erectus, were deliberately bringing fire into Wonderwerk Cave in South Africa as far back as 1.79 million years ago.
An international team of researchers led by Dr. Liora Kolska Horwitz of the Hebrew University of Jerusalem’s National Natural History Collections, working at the site of the oldest dated intentional use of fire by ancient human ancestors, South Africa’s Wonderwerk Cave, has found new evidence pushing that date even earlier into prehistory.
The research team behind the potentially history-altering findings said the discovery, which suggests that ancient hominins intentionally controlled fire, resulting in charred animal bones sometime between 1.07 and 1.79 million years ago, provides researchers with previously unavailable insights into how our ancestors first began to harness one of the most important tools in the evolution of human society and culture.
The study also introduced the archaeological community to a promising new method for analyzing burned bone samples by monitoring its light-emitting properties.
Intentional Use of Fire Provided Human Ancestors with a Critical Tool
According to a statement announcing the study, Dr. Horwitz, who is co-director of the Wonderwerk Cave project with Prof. Michael Chazan at the University of Toronto, and colleagues note the historical significance of fire, ranging from warmth and predator protection to extended daylight and the cooking of meat. However, historians have struggled to identify a single moment or historical period where humanity’s ancient ancestors first started to use fire intentionally.
“Evidence of fire from such ancient sites is often subtle and difficult to detect,” Dr. Horwitz explained.
Before the new analysis, the oldest agreed-upon evidence for intentional fire use also came from Wonderwerk Cave. Situated within the Kalahari Desert of South Africa, the cave provided evidence placing fire use to approximately 1 million years ago.
While that study used the most advanced techniques available, the team behind the new study decided to employ a non-invasive process that involves illuminating ancient bone fragments with specific wavelengths of light to determine whether they had been exposed to intense heat. In cases where bones have been heated to fire-like temperatures, the right wavelength of light will cause them to glow.
Remains Likely Left by Homo Erectus
Because evidence from ancient sites is scarce, the team’s non-invasive technique allowed them to study tiny fossilized rodent bones left in the cave by owls without damaging them. The team noted that using remains that accumulated naturally on the ancient cave floor provides an “independent, non-anthropogenic record” of ancient events within the local area.
White (#5 on right) is the most burnt, while yellow-beige (on left #1) is unburnt. Image Credit: Wonderwerk Cave Project.
After exposing the ancient bone to specific wavelengths of light, the team found what they described as “clear signs of burning.” Dr. Horowitz confirmed the findings, noting that the team’s analysis reveals “fire was repeatedly present deep inside Wonderwerk Cave.”
Because the deposits were found over 30 meters deep in the cave, the team ruled out wildfires as a possible source of combustion. The layer also lacked bat guano remains, which the team noted “rules out spontaneous combustion.”
A chemical analysis of the charred bones dated them to between 1.07 and 1.79 million years ago, redating the 2012 findings. Critically, the evidence for ancient fire use was in an archaeological layer “associated with artifacts” from the initial Acheulean period, which is consistent with the dating. If correct, this would make the likeliest early human ancestor that used fire Homo erectus.
Although the findings appear to extend the chronology of one of the earliest known records of fire use associated with hominins by as much as 790,000 years, the research team said the findings do not suggest that these early proto-humans could create fire “at will.” Instead, the likeliest scenario involves early human ancestors collecting fire from natural sources, such as lightning-induced wildfires on the African savanna, and bringing it into the cave.
“The early humans introduced this fire into the cave on multiple occasions and maintained it there before it eventually died out,” the team’s statement explained.
The team did not immediately pinpoint what methods these early hominins used to maintain a burning fire. However, they suggested that burning owl pellets as additional fuel may inadvertently have scorched the rodent bones.
A New Tool for Identifying Traces of Burning
When discussing the implications of the new, earlier date for the first intentional use of fire, Dr. Horwitz said the discovery shows that early human ancestors “were not simply passive observers of natural fires,” but instead were “actively engaging with fire and incorporating it into their lives.”
Beyond offering an earlier date range for early fire use, the work provides clues into how our ancestors used fire before they could make it on their own. The study also debuted a new, non-invasive, portable tool for investigating early fire use, which the study authors note “can be applied to large collections of fossils without damaging them.”
“Our study provides new tools for identifying traces of ancient burning,” Dr. Horwitz explained, with the team adding that application of this new technique to sites around the world “may help clarify the origins and development of one of the most consequential technologies in human history.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.
Geochemical analysis of 780,000-year-old stone tools from Israel suggests Acheulean (or Acheulian) hominins repeatedly sought specific basalt sources, revealing sophisticated planning and deep knowledge of their landscape.
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