Ancient footprints show how early human species coexisted

Preserved footprints in Kenya appear to record two different species of ancient humans walking along the same muddy lake shore, perhaps within days of each other. This is one of the most dramatic pieces of evidence ever discovered that multiple human species once coexisted in the world.

“It’s really unusual to find evidence of two different species walking on that surface,” said Kevin Hatala of Chatham University in Pittsburgh, Pennsylvania.

The footprints were discovered in 2021 in Koobi Fora, near the eastern shore of Lake Turkana in Kenya. They were first discovered by Turkana Basin Research Institute team member Richard Loki, Hatala said. “Originally there was a team of Kenyans working there.”

The research team discovered a track consisting of 12 footprints preserved in a layer of dry sand and silt (see image above). This was apparently left behind by one person walking in a straight line. Near the main group were also three isolated prints that appeared to have been made by three different individuals. The lack of mud cracks or signs of overprinting with other tracks indicates that these prints were all made at about the same time. “These sites are probably capturing time periods ranging from minutes to days,” Hatala says.

This deposit was determined to be approximately 1.52 million years old. Isolated footprints are similar to footprints left by modern humans. Your heel touches the ground first, then your foot rolls forward and you push off with the sole of your foot. Hatala and his colleagues suggest that these may have been fabricated. homo erectusis known to have lived in this area.

In contrast, continuous trajectories were created by flatter-footed hominins. Hatala and his colleagues suggest that this could be Paranthropus boiseianother type of hominin that lived in this area.

“Even if there are footprints, you can never be 100 percent sure who made them,” says Ashley Wiseman of University College London, who was not involved in the study. but, H. erectus and P.Boisei They are the only humans whose remains have been found preserved in this area, “so we can make an informed guess that it is these two individuals.”

If the track was really made by humans, P.Boisei Wiseman said the specimen appears to have been bipedal. The bones of the skull, arms, and legs are paranthropus“We’ve never found a skull associated with the rest of the skeleton,” she says, meaning little is known about their bodies beyond their heads, and the way they walk remains a mystery. The trajectory will be changed, saying, “This is clear evidence that it was walking on two legs.”

These two species were very different. H. erectus It was one of the earliest members of our genus. homo. They had larger brains than early humans and were the first clade to travel outside of Africa. in contrast, P.Boisei They had large teeth and jaws, small brains, and were apparently adapted to eating chewy foods like grasses and sedges.

Hatala and his team then looked at other known footprints found in the same area and at the same time, and found that they appeared to match either species. “Similar patterns have been seen at other sites, which may span more than 100,000 years,” he says. “These two species appear to have coexisted with each other in this same familiar landscape for a very long time.”

“If they were able to coexist for more than 100,000 years, we speculate that there was probably a low to neutral level of competition,” Hatala says. Previous research suggests that the two people were eating different foods. Unlike P.Boisei, H. erectus It is thought that they had a varied diet, including hunting large animals.

“Both of us were able to carve out our own existence within this shared landscape,” Hatala says. Subsequent changes in the environment may have had an effect. P.Boisei Potentially extinct, yet more adaptable H. erectus Survived.