More than a million years ago, in a hot savanna teeming with wildlife near the shores of Lake Turkana in Kenya, two completely different species of hominid may have passed each other as they scavenged for food.
Scientists know this because they examined 1.5 million-year-old fossils they discovered and concluded that they represent the first example of two sets of hominid tracks made around the same time on an ancient lakeshore. The discovery will provide more information about human evolution and how species cooperated and competed with each other, the scientists said.
“Hominin” is a newer term that describes a subdivision of the larger class known as hominids. Hominins include all organisms, extinct and living, considered to belong to the human lineage that arose after the split from the ancestors of the great apes. This is believed to have happened about 6 to 7 million years ago.
The discovery, published today in Science offers hard evidence that different species of hominid lived simultaneously in time and space, overlapping as they avoided predators and overcame the challenges of securing food in the ancient African landscape. The hominids belonging to the species Homo erectus and Paranthropus boisei, the two most common living human species of the Pleistocene epoch, made the tracks, the researchers said.
Their presence on the same surface, made close to each other in time, places the two species on the edge of the lake, using the same habitat.”
Craig Feibel, study author and professor in the Department of Earth and Planetary Sciences and the Department of Anthropology, Rutgers School of Arts and Sciences
Feibel, who has conducted research since 1981 in this area of northern Kenya, a rich fossil site, applied his expertise in stratigraphy and dating to prove the geological antiquity of the fossils to 1.5 million years ago. He also interpreted the depositional setting of the footprint surface, limiting the passage of the track builders to a few hours and showing that they formed in the same place in the soft sediments where they were found.
If the hominids didn’t cross paths, they crossed the coast within hours of each other, Feibel said.
While skeletal fossils have long provided the primary evidence for the study of human evolution, new fossil data are revealing fascinating details about the evolution of human anatomy and movement and giving further clues to ancient human behaviors and environments, according to Kevin Hatala, of study. first author and associate professor of biology at Chatham University in Pittsburgh, Pa.
“Fossils are exciting because they provide living snapshots that bring our fossil relatives to life,” said Hatala, who has been researching hominid footprints since 2012. “With these kinds of data, we can see how living individuals, millions of years ago years, they moved around their environment and potentially interacted with each other or even with other animals or stone tools.”
Hatala, an expert on leg anatomy, found that the species’ tracks reflected different patterns of anatomy and movement. He and several co-authors distinguished one set of footprints from another using newly developed methods to enable a three-dimensional analysis.
“In biological anthropology, we’re always interested in finding new ways to infer behavior from the fossil record, and this is a great example,” said Rebecca Ferrell, director of a program at the National Science Foundation that helped fund this part of the research. . “The team used state-of-the-art 3D imaging technologies to create a completely new way of looking at footprints, which helps us understand human evolution and the roles of cooperation and competition in shaping our evolutionary journey.”
Feibel described the discovery as “a little crazy.” Researchers discovered the fossils in 2021 when a team organized by Louise Leakey, a third-generation paleontologist who is the granddaughter of Louis Leakey and daughter of Richard Leakey, discovered fossilized bones at the site.
The field team, led by Cyprian Nyete, consists mainly of a group of highly trained Kenyans who live locally and scan the landscape after heavy rains. They noticed fossils on the surface and excavated to try to find the source. While cleaning the top layer of a bed, Richard Lockie, one of the excavators, noticed some giant bird tracks and then spotted the first human track. Leakey coordinated a response team that excavated the surface of the footprint in July 2022.
Feibel noted that it has long been assumed that these fossil human species coexisted. According to fossils, Homo erectusdirect ancestor of man, remained for another 1 million years. Paranthropus boiseiHowever, it disappeared within the next hundreds of thousands of years. Scientists don’t know why.
Both species were upright, bipedal, and highly mobile. Little is yet known about how these coexisting species interacted, both culturally and reproductively.
The tracks are important, Feibel said, because they fall under the category of “trace fossils” — which can include tracks, nests and burrows. Trace fossils are not part of an organism, but provide evidence of behavior. Body fossils, such as bones and teeth, are evidence of past life, but are easily moved by water or a predator.
Trace fossils can’t be moved, Feibel said.
“This proves beyond a shadow of a doubt that not just one, but two different hominids were walking on the same surface, literally within hours of each other,” Feibel said. “The idea that they lived at the same time might not be a surprise. But this is the first time it’s been proven. I think it’s really huge.”
