America’s first people survived a world in flux: 23,000-year-old footprints reveal how climate change reshaped their lives during the Ice Age

Over 20,000 years ago, when much of the Northern Hemisphere was suffering the effects of the last ice age, people were thriving in an environment that bore little resemblance to the modern American Southwest. In what is today known as White Sands National Park, in the state of New Mexico, a huge lake occupied the region, the surrounding mountains had conifer forests growing in them, and it was a few degrees cooler than today. Scientists have discovered new information about the environment in which these early Americans lived through the study of the famous human footprints at the park.

This information indicates that there were quite significant changes in the landscape in about 2,000 years, including warmer weather, changing vegetation and the drying up of the lake.

Also Read | Trump's shadow fleet loophole: Easing US sanctions on oil tankers may not lower fuel costs


This research follows previous research that has found the existence of human footprints at White Sands, which date back to about 23,000 years ago.

Such findings have contradicted previous theories about the timeline of how people populated America since this finding has shown that humans existed in this part of the world much earlier than previously known from archaeological studies.

The study, which was published in Science Advances, goes past the issue of the timing of when the people arrived. Instead, it studies the environmental changes taking place during their time.

A very different New Mexico during the last ice age

Approximately 24,200 years ago, Lake Otero was located in the White Sands area, which consisted of the surrounding landscapes that had conifer forests in nearby mountain ranges. As the researchers say, the temperature at that time was about 4°C cooler than the current one.

Such an ecosystem could hardly be compared with the dry environment typical for the region today. The lake and the vegetation represented a dynamic ecosystem that was constantly used by the first settlers.

Also Read | The US has $100 billion to break China’s rare-earth grip. Can it stop Beijing from holding America’s supply chain hostage?

In the next 2,000 years, there occurred a change in temperatures and landscape. The conifers disappeared, and their place was taken by oaks and sagebrush; the lake started to diminish, its salinity became higher, and the vegetation changed to a drier type.

These transformations are a sample of the environmental challenges that confronted the people who lived in the area.

While previously they had lived on a landscape that stayed unchanged throughout many generations, now they found themselves in a place where the availability of water, vegetation, and other natural resources might have shifted during one's lifespan.

According to Dr Sally Reynolds, an associate professor of hominin paleoecology at Bournemouth University and co-author of the paper, the findings allow the scientists to go further than just dating the footprints. They allow scientists to get some idea about the world in which these footprints were created.

However, it doesn’t mean that all changes required people to move or transform their lifestyles. It only suggests that the environment in which the early Americans lived was transforming.

Ancient pollen and chemical traces reveal a changing climate

To restore the landscape, the researchers studied the sediments of the White Sands area, which were rich in fossilised pollen indicating information about vegetation in that area throughout the time period in question.

The organic compounds found in the sediments were also analysed. Those compounds consisted of leaf wax and archaeal/bacterial membrane lipids. Such analysis enabled scientists to study precipitation and temperature, as well as aridity in the area.

Also Read | Can a private company switch off a country’s battlefield communications? The Starlink-Ukraine crisis exposes a new vulnerability in modern warfare

Therefore, it is through such an approach that scientists have been able to understand the changes taking place in the environment that are not evident from the footprints.

While the footprints are informative in showing the specific moments when people used to walk there, the sediments will reveal more information regarding the general environment.

Kathleen Springer, research geologist for the US Geological Survey and co-author of the study, stated that the research has been able to meet one of the many goals set by researchers in White Sands, which was to expand on the original footprint site and gather environmental evidence to understand the conditions at the Last Glacial Maximum.

It is important to mention that reconstructing past environments could be helpful in understanding ancient findings.

At the same time, the research cannot tell the story of individual responses to these changes. Environmental evidence shows that change occurred, but the response of individuals remains unknown.

Did a shrinking lake attract early Americans?

One possibility offered by the researchers is that the changes in the environment may have been the reason for people continuing to use the White Sands area.

With the decrease in the lake, the concentration of animals and plants might have increased in certain spots, which could have made this particular area attractive for obtaining food.

It is important to remember that this is only a hypothesis and not the definite answer to the reasons for human actions. It is clear that people inhabited the area during all the environmental changes, but it is impossible to determine precisely what kind of food they obtained, where they moved, or how they adapted to the changes.

In the case of the oldest evidence of human presence in the Americas, it is vital to keep in mind the difference between the footprints left by the people.

Reynolds studied the footprints as if they were still pictures as opposed to moving images.

They provide a snapshot in time of when humans, mud, water, and chance came together in one place. In combination with the environmental data, this allows scientists to reconstruct a richer image of the environment in which the early Americans thrived.

Previous work by Reynolds, Matthew Bennett and others at the US Geological Survey, however, had also been analysing the evidence for early human transport technology among the residents of White Sands.

None of this previous work, nor this new environmental analysis, is capable of revealing all of the details of how people moved about in their environment.

The findings, then, put new information into the context of what is already a very important archaeological site.