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Mikhail Polyakov

Footprints at White Sands, New Mexico: what pollen reveals about the climate in which people walked 21,000 to 23,000 years ago

Level: BeginnerReading time: 4 min

Topics: History, Science

A line of shallow footprints filled with water on a white sandy plain, with a shallow lake and conifer-covered mountains behind at dawn

Short answer: researchers studied ancient pollen in the rocks of White Sands National Park in New Mexico, where there are human footprints that the same scientists previously estimated to be about 21,000 to 23,000 years old. The pollen showed that over roughly two thousand years the lake shrank and conifer forests gave way to oaks and sagebrush. The authors conclude from this that people stayed in these places while nature around them changed quickly. But the age of the footprints themselves is debated, and little is known about the people's behaviour from them. Below: what is established and what remains an assumption.

What was studied

There is one source: a Live Science article about a study published on Wednesday, 14 October, in the journal Science Advances. I have not read the scientific paper itself.

  • Where. White Sands National Park in New Mexico. It is home to an archaeological site regarded as the place of the oldest human footprints in the Americas.
  • Age of the footprints. The same researchers previously dated the footprints to about 21,000 to 23,000 years. According to the text, the age remains a subject of scientific debate because it is significantly older than other Indigenous sites in the Americas.
  • What was taken for analysis. Ancient pollen from the park's rocks, as well as plant leaf waxes, bacterial membrane lipids and other organic molecules. They were used to judge the environment of the time.
  • Period. The coldest era of the last ice age, the so-called Last Glacial Maximum, roughly 26,500 to 19,000 years ago.

What the analysis showed

According to the text, about 24,200 years ago White Sands had a large lake, and the surrounding mountains were covered with conifers (pine, fir and spruce). Over the next two thousand years temperatures rose, the lake shrank, and the conifers were replaced by oaks and sagebrush.

Co-author Kathleen Springer of the US Geological Survey said that early people in this area were witnesses to rapid changes in the environment, noticeable on the scale of a human lifetime. Co-author Sally Reynolds of Bournemouth University (UK) added that the layers containing the footprints show how the environment changed significantly within the lifetimes of individual people, while people kept coming to and living in this area.

What remains an assumption

  • Why they returned. The researchers suggest that people might have come at different times because of the changing climate: a shrinking lake could have gathered more animals and plants in one place. This is only a guess.
  • What the footprints do not show. Reynolds noted that the footprints give a snapshot of people who lived there more than 20,000 years ago, but they are "not a continuous movie, but individual frames": moments when people, mud, water and chance came together. Little is known about people's behaviour from the footprints.
  • Age. The dating of the footprints is disputed. Some scientists object to the methods, but, as the text says, evidence is accumulating that they are about 23,000 years old.

Why this matters

If the footprints really are that old, they indicate that people came from Asia to the Americas via the region of the Bering Strait noticeably earlier than researchers previously thought. Previously the prevailing assumption was that people appeared on the continent about 13,000 years ago. At White Sands, later footprints have also been found, for example those of an adult and a small child about 10,000 years old, as well as drag marks next to the footprints. According to the text, they point to a travois: a wooden frame of two bound poles on which people probably transported goods. Among the animals of that era the text names mammoths and giant ground sloths.

What is a finding here, and what is a conclusion

This is my own arrangement, not words from the source.

  1. Measurement. Pollen and organic molecules from the rocks: there was a lake, then it shrank, and forests changed.
  2. Joining two things. The dating of the footprints and the climate from pollen are put together: at this age of the footprints, people saw these changes. This is a conclusion, and it depends on the age of the footprints, which is disputed.
  3. A guess. People may have returned because of the shrinking lake and plentiful game.

How to read such news. Ask what a conclusion rests on: a measurement (pollen, molecules) or a link between two measurements (climate and the age of the footprints). The second is weaker than the first and depends on the most disputed number.

Summary

Pollen and other organic traces from White Sands show that during the two thousand years after about 24,200 years ago the lake shrank and conifer forests were replaced by oaks and sagebrush. If the footprints there really date to 21,000 to 23,000 years ago, as the authors believe, then people lived through these changes. The dating is disputed, and the reasons people returned remain a guess.

See also another piece in this section: How many people lived in the Americas before Columbus.

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