Drastic Changes 400,000 Years Ago Pushed Humans To New Behaviors, Sophisticated Tools

A team of researchers found that a critical shift in human behavior and adaptability was possibly due to a combination of factors that began 400,000 years ago.

Early humans in the East African Rift Valley led the same way of life for 700,000 years. During that period, they used the same tools, adopted the same practices and had the same lifestyle. But artifacts recovered at the Olorgesailie archaeological site had previously suggested a major shift in the early humans' lifestyle starting some time 320,000 years ago

The early humans shifted to using more sophisticated tools and started trading with distant groups. They even began using coloring materials, which the Smithsonian news release about a new study explained was suggestive of symbolic communication.

There was evidence that animal inhabitants also changed at the time, with the large grazing animals dying out.

So what happened during that time that caused the sudden change?

To find out, the researchers of the new study used the 139-meter core that was drilled from the nearby Koora basin. This gave them access to 1 million years of environmental data and allowed them to essentially reconstruct the conditions at the time, thus giving them a glimpse of what caused the humans to adapt to their new environment.

The researchers found, unlike some scientists' supposition that climate change alone could have caused the drastic change, there were actually a number of other factors that essentially forced the humans to adapt, the Smithsonian news release explained.

Specifically, the researchers found tectonic activity in the region reshaped the environment -- shrinking or draining huge lakes and raising hills and cliffs -- beginning 400,000 years ago. This tectonic activity led to major changes in the environment, including making it more prone to water supply fluctuations and vegetation changes. And because there was less grass to feed on, this likely caused the large grazers to die out and be replaced by the smaller mammals with varied diets.

"Beginning ~400 ka ago, tectonic, hydrological, and ecological changes combined to disrupt a relatively stable resource base, prompting fluctuations of increasing magnitude in freshwater availability, grassland communities, and woody plant cover," the researchers wrote. "Interaction of these factors offers a resource-oriented hypothesis for the evolutionary success of MSA adaptations, which likely contributed to the ecological flexibility typical of Homo sapiens foragers."

Simply put, the researchers found that it wasn't just climate change that changed the environment but a combination of various factors.

"Some pretty radical things were going on here," study lead Richard Potts of the Smithsonian National Museum of Natural History said, according to the Smithsonian Magazine. "A change began from reliable living conditions to an era of uncertainty and repeated disruption in those crucial conditions for life."

Taken together, this new environment essentially pushed the humans to adapt to their new environment, leading to new, critical behaviors. So instead of moving out of the region or going extinct, the early humans made major leaps in their behavior and culture.

The researchers noted, however, that the way the humans adapted to the extreme environment does not necessarily mean that we can endure the changes we are experiencing now.

"We have an astonishing capacity to adapt, biologically in our genes as well as culturally and socially," Potts said in the Smithsonian news release. "The question is, are we now creating through our own activities new sources of environmental disruption that will continue to challenge human adaptability?"

The study was published in Science Advances.