Footprints in sand made 1.5 million years ago reveal something shockingly unexpected

Nearly 1.5 million years ago, two species of humans lived alongside each other, may be aware of the existence of the other and even interact. A study has revealed that the two species of ancient humans crossed paths on a lakeshore in what is now modern-day Kenya. That ancient lakeshore is part of the Koobi Fora fossil site.

The revelation was made by fossilised footprints in the sand in the area that have preserved the unexpected and extraordinary moment. Scientists say they likely lived as friendly neighbours instead of squabbling over their differences. 

The study was published in the journal Science on Thursday (Nov 28).

"Their presence on the same surface, made closely together in time, places the two species at the lake margin, using the same habitat," geologist and anthropologist Craig Feibel of Rutgers University in the United States said.

The footprints were so closely made that they indicated that the two species passed each other in this area within hours to a couple of days.

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Kevin Hatala, first author of the study and an associate professor of biology at Chatham University in Pittsburgh, said, “We see them in the very same lake margin environment, passing within this area within hours to a couple of days of one another."

"They probably would have been aware of each other’s existence. They saw each other and they might have interacted,” added Hatala.

Footprints in Kenya

The footprints at Koobi Fora were first spotted in 2007. They are the oldest known example of hominins walking upright like modern-day humans. In the same region, the skeletal remains of several ancient human relatives have also been found. 

More footprints have been found since then, with the most recent ones in 2021. Scientists noted deep and perfectly preserved prints gouged out of what was once soft, squishy mud. They were covered with sediment over time, but Hatala's team excavated them in 2022. 

“There’s one long trackway with 12 (hominin) footprints in it. It was made at a decent walking pace … especially since they were walking through mud. There’s not a clear destination at the end,” Hatala said.

They lived peacefully

The researchers discovered that based on the imprints, two distinct walking styles existed at the time. They were made by two different species of hominin and both inhabited the site. The prints appear in the same sediment layer, which led them to conclude that they were made at the same time.

Researchers say that the two species coexisted with each other because they had different diets and lifestyles. They did not have to compete with each other, and so lived peacefully.

They are confident that the footprints were made within hours to a few days of one another since there is no cracking on the surface of the footprints. That would have happened if they were exposed to air.