The first proof that two distinct species of early human ancestors visited the same area at the same time 1.5 million years ago comes from a recently found set of footprints in Kenya.
The footprints, which were discovered within hours or days of each other and are said to be those of the species Homo erectus and Paranthropus boisei, raise fresh questions about what transpired when the two came into contact, according to the researchers who made the discovery.
The footprints were buried in silt at a well-known fossil site and encased in dried mud close to a lake in northern Kenya, according to a report on the finding that was published Thursday in the journal Science.
Researchers discovered that the two sets of prints were different by examining their forms and striking patterns; they came to the conclusion that the best explanation was that two unique animals had left the tracks.
The finding contributes to anthropologists’ and paleontologists’ increasing comprehension that early human relatives most likely interacted and coexisted. Consequently, it calls into question the nature of the species’ connection.
We believe that the two species that were there, these individuals, would have likely known that there were other species in the area.
Kevin Hatala, an assistant professor of biology at Chatham University and a main author of the study, stated, “It begs the question of what those interactions would have been like because they would have seen each other and recognized each other as different species.” Were they rivals? Were they completely comfortable with each other’s presence?
The latest discovery offers proof of direct overlap, even though previously found fossil bones of Paranthropus boisei and Homo erectus indicated that both species had formerly resided in the area.
It also demonstrates how the two species’ two-footed gaits differed greatly. Despite being related to humans, Homo erectus and Paranthropus boisei had rather diverse characteristics, and their paths within the human evolutionary tree diverged significantly.
From the neck down, Homo erectus’ anatomy resembled that of a human. The species may have cooked over fire and utilized stone tools. Its members probably ate meat as part of their diversified diet.
After the recently found footprints were formed, the species continued to exist for almost a million years, eventually spreading to Asia, Indonesia, and other places. A little more than 100,000 years ago, Homo erectus made its last appearance in the fossil record.
“A lot of people have believed that they are the best candidate to be our direct ancestor,” Hatala stated. “They appear to be a highly prosperous species.”
In contrast, Paranthropus boisei had huge molar teeth, enormous chewing muscles, and smaller brains. Not participating in the study, William Harcourt-Smith, an associate professor of anthropology at Lehman College, said the species probably developed to consume difficult meals like hard nuts or to ingest rough, low-quality foods like shrubby plants.
Compared to Homo erectus, the species did not survive on Earth for nearly as long.
Regarding the period of time when the footprints were found, Hatala stated, “They are believed to have gone extinct not too long after this, within the next few hundred thousand years.” No one is certain of what occurred, he said, although it’s plausible that environmental changes limited their specialized diets.
While searching for additional fossils, the footprints were first found in 2021 in a location known as Koobi Fora. Because elevating rock reveals ancient sedimentary layers at the surface, researchers may access the bones of extinct people and other creatures, making the location a fossil hotspot.
The next year, a group of around twelve tracks that seemed to walk in a line were discovered by researchers, who also discovered a second set of footprints that ran perpendicular to the first.
We believe that these imprints were created in the mud near the lake. Sediment was brought in over it by some event. The footprints may have been covered shortly after they were produced by sediments carried in by a minor flood or a rise in the water level, according to Hatala.
Before being covered by sand, the muddy impressions didn’t appear to be cracked or trodden down by other animals. According to the experts, that indicates that they were separated by only a few hours or days.
According to Hatala, “the sediment shielded them, kept them from breaking, and permitted their inclusion in the geologic record.”
Because their diets were so dissimilar, he and his co-authors believe the two species may have been able to coexist in the region. They could have had a hostile relationship and competed for resources. For hundreds of thousands of years, the species appear to have resided in the same geographical region.
According to Harcourt-Smith, a research associate in paleontology at the American Museum of Natural History, the site was unusual and the researchers’ analysis was sound.
“I really want to emphasize how unique this site is, how special it is, and how much of an opportunity we have to learn more,” he added.
In general, it has become more evident that throughout the course of the last 7 million years of evolution, multiple ancient human species interacted across diverse ecosystems, Harcourt-Smith continued. There are several side branches and animals like Paranthropus boisei that signify an evolutionary dead end along the evolutionary road leading to modern humans.
“There is a lot of experimenting and human evolution is complex and untidy. He stated, “It’s not a straight line.”
Scientists have discovered genetic and archeological evidence in recent decades that indicates human, Denisovan, and Neanderthal ancestry overlapped and occasionally interbred. Interbreeding is not discussed in the current study, but it does make it more evident that even earlier species overlapped and interacted more than was previously thought.
According to Craig Feibel, another study author, the researchers covered up the footprints for future generations after finishing their work at the Koobi Fora location, where they took pictures and recorded them in a variety of ways.
“To prevent erosion, they must carefully rebury it with sediment that won’t harm the footprints,” he stated.
