Even before modern climate records were available, ancient pollen found in rocks was silently recording a major change in the New Mexico landscape — a change which early humans might have seen during their own lives.
A study of ancient pollen and organic remains from White Sands National Park reveals that humans living in the area more than 20,000 years ago experienced significant environmental shifts, including rising temperatures, a shrinking lake, and vegetation changing from conifer forests to oak trees and sagebrush. This provides context for the park’s famous ancient footprints, dated to roughly 21,000-23,000 years ago.
The footprints and pollen records together suggest humans continuously inhabited the region despite dramatic ecological changes occurring within individual lifetimes. While footprints capture brief moments of human activity, pollen data reconstructs broader environmental conditions. These findings contribute to ongoing debates about when humans first arrived in the Americas, challenging the previously accepted 13,000-year timeline, though dating methods remain under scientific scrutiny.
A recent study of pollen and other microscopic remains of ancient life at White Sands National Park indicates that humans who lived in the area more than 20,000 years ago went through considerable environmental changes as temperatures increased, the large lake retreated, and the surrounding vegetation changed from conifer forests to oak trees and sagebrush.
The results provide a rare insight into the world lived in by some of the first people in North America, since their footprints, preserved in the sediments of the park, are at the heart of the current debate concerning the first arrival of humans in the Americas.
“It’s remarkable that early humans in the region were real-time witnesses to a rapidly changing environment discernible within a human lifetime — that is really food for thought,” said study co-author Kathleen Springer, a research geologist at the U.S. Geological Survey, in a statement.
The study introduces an environmental aspect to the archaeological findings at White Sands, the ancient footprints there having been dated to about 21,000 to 23,000 years ago. Should these dates prove accurate, the footprints indicate that humans were in the area some thousands of years before the previously accepted figure of around 13,000 years ago for when people first arrived in the Americas.
Scientists are still discussing the age of the footprints, even though further evidence has made it more likely that the occupation dates from about 23,000 years ago.
A record of a changing world
In order to reconstruct the landscape, the researchers looked at ancient pollen that had become trapped in rock and sediment samples from White Sands.
Pollen gives hints as to the plants which used to grow in a particular area; scientists are able to reconstruct changes in the vegetation by identifying the various types that have been preserved over time and thus deduce how environmental conditions changed.
The samples also included leaf waxes, bacterial membrane lipids and other organic molecules which enabled the researchers to study the region’s past conditions.
Their analysis showed that the landscape had undergone significant changes over a relatively short period.
About 24,200 years ago there was a big lake at White Sands and the adjacent mountains were wooded with conifer trees such as pines (Pinus), firs (Abies) and spruces (Picea).
For the next 2,000 years the temperature increased and the lake started to shrink; the coniferous vegetation was replaced by oak trees (Quercus) and sagebrush, the researchers found.
The fact that the transition shows that the environment in the region was not static even during the coldest phase of the last ice age, but rather the landscape was reacting to changing climatic conditions while people kept on going to and living in the area.
For the original inhabitants, the changes could have influenced the amount and spread of water, plants and animals. It is not possible for the pollen record to exactly show how each person experienced the transformation or how they adjusted to it.
Footprints capture moments in human history
White Sands is famous for having an exceptional assortment of prehistoric footprints which record various moments in the lives of both people and animals that once walked across the area.
The tracks consist of footprints assigned to humans who walked beside Ice Age animals such as mammoths and giant ground sloths; other findings provide insight into human relationships and everyday activities, such as footprints thought to have been made by a caregiver who was looking after a toddler about 10,000 years ago.
Sled-like drag marks have also been found beside the ancient human footprints. They could be evidence of a travois — that is, a simple transport frame consisting of two poles tied together — which people might have used to carry their belongings over the landscape.
The fact that these discoveries have been made indicates that White Sands was not just a place which people briefly visited; rather, it was a landscape that humans used over thousands of years, providing them with access to resources and the opportunity to move around the area.
The additional information provided by the new pollen analysis shows the way in which the surrounding environment had changed during the period when the early humans were there.
“Throughout these periods of change, the people continued to visit and live in this area,” said study co-author Sally Reynolds, a paleoanthropologist at Bournemouth University in the United Kingdom.
“The sediments containing their footprints show us their environment changed significantly within individual human lifetimes,” she said.
A shrinking lake
The researchers proposed that individuals might have gone to White Sands at different times in order to make the most of the changing environmental conditions.
When the lake decreased in size, animals and plants could have become concentrated around the remaining water supplies and appropriate habitats, which might have made certain resources easier to locate.
The fact that this possibility exists provides one explanation for the continued visits by humans as the landscape changed. Yet it is still only a hypothesis and not a confirmed account of how people made their decisions or obtained their food.
It is possible to tell that people were at a certain place and time from footprints, but they tell us very little about their motives, their diets, their social structure or the way they reacted to environmental pressures.
“The footprints give us a snapshot of the people who lived there over 20,000 years ago,” Reynolds said.
“But they are not a continuous movie of their lives. They are individual frames — showing moments when humans, mud, water and chance came together.”
That point is important since the tracks record only brief interactions between people and their environment, whereas pollen and other biological remains are useful for reconstructing the wider environmental changes taking place around them.
No single record is sufficient on its own to show how the early inhabitants lived; but together they do enable researchers to set human activity within the changing ecological landscape.
Implications for the peopling of the Americas
The findings also play a part in the wider scientific debate concerning the first time when humans arrived in North America.
For many decades the prevailing theory was that humans had reached the continent some 13,000 years ago, this being connected with the emergence of particular archaeological evidence associated with the Clovis culture.
The evidence obtained at White Sands contradicts that timeline by showing that humans had already been in the area which is now New Mexico by several thousand years.
The suggested dates have come under scrutiny since they are much earlier than many other well-known archaeological sites in the Americas, and questions regarding the dating methods have meant that the White Sands findings are still the subject of scientific debate.
The study alone doesn’t establish when or how the first Americans arrived; rather, it aids in reconstructing the environmental conditions in which people lived, assuming the early dates are correct.
The growing picture shows that the landscape is experiencing major changes, with human activity still visible together with evidence of evolving plant communities and altered water conditions.
The pollen from ancient times cannot give a full account of the people’s lives. But it can show what the world was like.
