Ancient Footprints Push Back Date of Human Arrival in the Americas
Human footprints found in New Mexico are about 23,000 years old, a study reported, suggesting that people may have arrived long before the Ice Age’s glaciers melted.
By Carl ZimmerSept. 23, 2021Updated 2:22 p.m. ETSign up for Science Times Get stories that capture the wonders of nature, the cosmos and the human body. Get it sent to your inbox.
Ancient human footprints preserved in the ground across the White Sands National Park in New Mexico are astonishingly old, scientists reported on Thursday, dating back about 23,000 years to the Ice Age.
The results, if they hold up to scrutiny, would rejuvenate the scientific debate about how humans first spread across the Americas, implying that they did so at a time when massive glaciers covered much of their path.
Researchers who have argued for such an early arrival hailed the new study as firm proof.
“I think this is probably the biggest discovery about the peopling of America in a hundred years,” said Ciprian Ardelean, an archaeologist at Autonomous University of Zacatecas in Mexico who was not involved in the work. “I don’t know what gods they prayed to, but this is a dream find.”
For decades, many archaeologists have maintained that humans spread across North and South America only at the end of the last ice age. They pointed to the oldest known tools, including spear tips, scrapers and needles, dating back about 13,000 years. The technology was known as Clovis, named for the town of Clovis, N.M., where some of these first instruments came to light.
The age of the Clovis tools lined up neatly with the retreat of the glaciers. That alignment bolstered a scenario in which Siberian hunter-gatherers moved into Alaska during the Ice Age, where they lived for generations until ice-free corridors opened and allowed them to expand southward.
But starting in the 1970s, some archaeologists began publishing older evidence of humanity’s presence in North America. Last year, Dr. Ardelean and his colleagues published a report of stone tools in a mountain cave in Mexico dating back 26,000 years.
Other experts have been skeptical of such ancient finds. Ben Potter, an archaeologist at the Arctic Studies Center at Liaocheng University in China, said that some of these supposed tools might actually be oddly shaped rocks. Dr. Potter also questioned some of the dates scientists have assigned to their finds. If a tool sinks into underlying sediment, for example, it may appear to be older than it really is.
“There are unresolved issues with every single one of them,” Dr. Potter said of the older purported sites. “None of them are unequivocal.”
The study at White Sands now adds a new line of evidence for an early arrival: Instead of tools, the researchers have found footprints.
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The footprints were first discovered in 2009 by David Bustos, the park’s resource program manager. Over the years, he has brought in an international team of scientists to help make sense of the finds.
Together, they have found thousands of human footprints across 80,000 acres of the park. One path was made by someone walking in a straight line for a mile and a half. Another shows a mother setting her baby down on the ground. Other tracks were made by children.
“The children tend to be more energetic,” said Sally Reynolds, a paleontologist at Bournemouth University in England and a co-author of the new study. “They’re a lot more playful, jumping up and down.”
Mathew Stewart, a zooarchaeologist at the Max Planck Institute for Chemical Ecology in Jena, Germany, who was not involved in the study, said that the evidence that humans had left the footprints was “unequivocal.”
The footprints were formed when people strode over damp, sandy ground on the margin of a lake. Later, sediments gently filled in the prints, and the ground hardened. But subsequent erosion resurfaced the prints. In some cases, the impressions are only visible when the ground is unusually wet or dry — otherwise they are invisible to the naked eye. But ground-penetrating radar can reveal their three-dimensional structure, including the heels and toes.
Mammoths, dire wolves, camels and other animals left footprints as well. One set of prints showed a giant sloth avoiding a group of people, demonstrating that they were in close company.
“What is fascinating about the study of footprints is that they present snapshots in time,” Dr. Stewart said.
The work of determining the age of the prints fell to Jeffrey Pigati and Kathleen Springer, two research geologists at the United States Geological Survey.
In 2019, they went to White Sands to get a feel for the site. Walking around some of the footprints, the researchers sometimes came across ancient seeds of ditch grass that had grown by the lake. In some spots, the abundant seeds formed thick blankets.
The researchers brought some of the seeds back to their lab and measured the carbon in them to determine their age. The results came as a shock: The ditch grass had grown thousands of years before the end of the last ice age.
Dr. Pigati and Ms. Springer knew those numbers would be controversial. So they embarked on a far more ambitious study. “The darts are going to start flying, so we better be ready for them,” Dr. Pigati recalled.
The scientists dug a trench near one cluster of human and animal footprints to get a tighter estimate of their age. On the side of the trench, they could see layer after layer of sediment. Carefully mapping the surrounding ground, they were able to trace the footprints of humans and animals to six layers in the trench, interspersed with eleven seed beds.
The researchers collected ditch grass seeds from each bed and measured their carbon. These measurements confirmed the initial results: The oldest footprints at the site — left by an adult human and a mammoth — were located below a seed bed dating back about 22,800 years.
In other words, the people who left the footprints walked around White Sands about 10,000 years before the Clovis people. The youngest footprints, the researchers estimated, dated to about 21,130 years ago. That meant that people lived or regularly visited the lake for about 2,000 years.
“This is a bombshell,” said Ruth Gruhn, an archaeologist at the University of Alberta who was not involved in the study. “On the face of it, it’s very hard to disprove.”
Dr. Potter praised the White Sands team for their care in the new study, saying that it is the strongest case yet made for people in the Americas before 16,000 years ago. But he would feel more confident in the extraordinary age of the prints, he said, if there were other lines of evidence beyond the ditch grass seeds. The seeds could have absorbed older carbon from the lake water, making them seem older than they really are.
“I’d like to see stronger data, and I don’t know if it’s possible to get stronger data from this particular site,” he said. “If it’s true, then it really has some profound implications.”
If humans were well established in New Mexico 23,000 years ago, they must have started spreading down from Alaska long before that. “That starts to wind back the clock,” said Dr. Reynolds of Bournemouth University.
Some researchers have argued that people could have spread through the Americas even when the glaciers were at their peak. Instead of traveling down the mainland, they could have moved along the coast. Alternatively, Dr. Ardelean and his colleagues have proposed that people traveled inland more than 32,000 years ago, before Ice Age glaciers reached their maximum extent and blocked off that route.
Dr. Gruhn argued that both scenarios remained possible in light of the new evidence from White Sands. It would take more work to find earlier sites that favored one of them over the other. “We’ve got a lot to do,” she said.
Mr. Bustos and his colleagues have more investigations planned at White Sands. They want to learn about the behavior of the people who left their footprints there. Did they hunt the animals around them? Did they live permanently at the lake or just pay it visits?
They must work quickly. The erosion that has revealed the footprints will erase them from the landscape in a matter of months or years. Countless footprints are disappearing before the scientists even lay eyes on them.
“It’s kind of heartbreaking,” Mr. Bustos said. “We’re racing to try to document what we can.”
Posted in Origins and tagged ancient humans, archeology, history, human migration, research by Charles Sheldon with no comments yet.
During the last, say 150 years there has been unrelenting and consistent technological change in nearly all areas – medicine, communications, travel, energy, the list is seemingly endless. It is almost unbelievable, actually. Somehow there seems to have been a parallel assumption that we humans have also changed greatly, maybe because we think we must have changed to bring forth all these marvels, and maybe, even more, many of us think that with all these new wonderful tools the measure of people, their character and behavior, must be changing rapidly as well. There has been, for at least six or seven generations, a steady belief in inevitable progress in all areas, including the character and behavior of humans.
This is a huge, huge mistake, in my opinion, because human nature hasn’t changed despite all these technological breakthroughs. The evidence of our own eyes and memories, for those of us who have been around for eight or nine decades, is exactly the opposite, as is the historical record – we humans have been bad to each other, always and forever.
Go way back, way way back, before farming, before towns and cities, the time of great ice and terrible animals, and humans barely hanging on in remote safe places. When a group invaded another group’s territory, back then, it seems they captured the women and children but killed off all the men, all of them, so there would not be retribution. Surely humans then, and in the years since, and today, are selfish, vengeful, hateful, lustful, cruel, possessive acquisitive, tyrants, murderers, just as humans are loving, caring, friendly, empathetic, self sacrificing, and noble.
Look over the last 150 years – many huge wars, hundreds of millions dead, maybe 70 million in the two World Wars alone. Millions more killed with famine, whether in China, Russia, India, Asia, or elsewhere. Millions more lost to disease. Remember that a century ago only smallpox had been defeated, there remained the scourge of measles, mumps, whooping cough, scarlet fever, polio, rickets, cholera, not to mention millions more lost to raw poverty. Yes, it is true that today millions of people are living far better than their forebears, but does this mean human nature has changed? That the legacy of grim news that has underpinned all the technological triumphs will somehow miraculously end?
I think not. Somewhere in the rush to greatness, and the ability to build and invent great things, we seem to have entirely lost awareness that we are both good and evil, flawed and noble, and any excess – ANY – promises difficulty, death, destruction. Nowadays we may look back and consider earlier people cautious, conservative in behavior, keeping their heads down, but maybe the truth of the matter was they were raised humble, cautious, well aware of their own dark side, and the dark sides of others. Throughout all of history the battles have remained the same – on the one had wresting survival from a hostile world, which we humans successfully did such that the world seems now to be ours, but on the other hand always, since the beginning, struggling with the much larger danger – ourselves, our conflicts and fights, and these days our narrative driven views that only we are right and all others not only flawed but even evil.
In ancient times, when we were not the apex predator, the world was above us, more powerful, and we were careful, humble, cautious, because we had to be. Now we rule the world, but it has not been the world that has brought evil, it is ourselves, plain as day, brought forth in the urgency of ideology and zealotry and certain-ness, and further complicated because the public megaphones respond to only anger, rage, froth. My sense is the greater mass of us are sick of all of it, and want to just get on with our lives, as best we can, and all of us know that only through humility will come the wisdom to regain some kind of balance.
Posted in Blog Posts, Humility and tagged history, human nature, humility, philosophy, struggle by Charles Sheldon with 1 comment.
This doesn’t look like much but it is astounding. This is a piece of bone found about 40 years ago in Sequim, Washington – a mastodon skeleton was discovered when Mr. Manis was digging out a pond on his field on the Olympic Peninsula. A mastodon is sort of like an elephant but a little smaller. The little lighter thing in the middle is actually a spear point, stuck in the bone, also of mastodon bone. There is a sweet but tiny exhibit in Sequim that displays the bones and this point and I took the picture when I visited few weeks ago. Here’s the thing. This bone, and spear point in it, have been dated to 13,800 years old. It is one of the oldest, if not THE oldest, proven evidence of early humans in North America, right here on the Olympic Peninsula in the shadow of Olympic National Park. People used to think the great ice covered this area that long ago, but apparently not. Apparently parts of the peninsula were a refuge from the ice, and maybe the hunters who took this animal lived there.
Posted in Origins and tagged Animals, history, ice age, olympics by Charles Sheldon with no comments yet.