Footprints in the Sand, the sequel

But there are footprints in real life too, less terrifying but they tell stories nonetheless. A few years ago, I wrote about sloth footprints here at White Sands National Monument in New Mexico, US (bit.ly/3F54Vbz). You and me and anyone else, I think, might have been mildly intrigued – it’s not every day that I run into either sloths or their footprints – but not anymore. But these prints attracted the interest of a team of scientists. Why? Because they were 11,000 years old. But that was not the only thing. Inside a large dull footprint was the imprint of a tiny foot—and it was human. There were many more, human prints inside sloth prints.

In fact, the researchers concluded that all those years ago, some tiny human—a child, most likely—”was deliberately running within the sloth track. I hope the sight of a playful baby caught you like it did. Caught me. There was a lot more they had extracted from the sloth print. Specifically, about that long encounter between sloths and humans; about the possibility that humans caused that sloth species to go extinct. helped.

In addition, these special human footprints supported the generally accepted theory of when humans appeared in the Americas. Various tools found in the city of Clovis, also in New Mexico, date back about 13,000 years, and are the oldest such tools found on the continent. As far as theory went, this made sense, as the last ice age had almost ended long ago. The glaciers then began to retreat, returning to the far northern latitudes. This allowed humans who had crossed from Siberia into Alaska to move further south-north and eventually into South America.

Like I said, this is a generally accepted theory, and most of the evidence found so far supports it. Unless… some of those same scientists pointed out that those human footprints in White Sands are not 11,000, but 23,000 years old (bit.ly/3maQydk). That is, humans were already south of those glaciers long before the retreat. how did this happen? But before answering that question, let’s look at two angles related to this story.

First, the Clovis theory has been challenged in recent years. Up and down the Americas, archaeologists have found other sites that suggest a human presence there earlier than 13,000 years ago. There is a site in Washington state where the rib of an ancient mastodon appears to have the tip of a spear. That bone was found to be 14,000 years old. Looks like a campsite in far-southern Chile. Carbon-dating of the wood showed that it was 14,600 years old. Both of these discoveries were written about in the late 1970s. However, keeping them in considerable shade, there is a site in Southern California. Archaeologists studying it reported in 2017 that “the hammer and stone anvil are in spatio-temporal association with the fragmentary remains of a single mastodon”. And the “radiometric analysis of several bone samples” from the site threw up a truly incredible age: 130,000 years.

Nevertheless, even these discoveries have been heavily skeptical. Scattered tools for an example- were they really strange shaped rocks or pieces of bone? Marks on bones, for another – were they done naturally, or perhaps even by modern archaeologists? Can we be sure that mastodons were actually killed by humans?

Second, while the footprints are remarkable, almost tangible evidence of human presence, their age is also difficult to determine. In fact, they are just part of the rock layers in the White Sands, and Matthew Bennett, lead author of this paper told Nature magazine, “Dating [rock layers] is a nightmare.” Yet, two years ago, his co-author David Bustos found that a set of these footprints seemed to be “right in the layers of rock-hard sediment”—and that this particular location gave an indication of its age. Introduced another way of estimating .

Scattered in the rock, in addition to the footprints, were preserved seeds of a weed called spiral dichgrass. It is an aquatic plant, and large clusters of it may have once grown here on the shores of an ancient lake that has long since dried up. But a large number of seeds were left behind and preserved in sediments over millennia. Bustos and his colleagues collected a lot of them, because organic material is relatively easy to carbon-date.

When they discovered the age of the seeds, the scientists were shocked. Because they predate the last ice age. Knowing that this result would attract scrutiny and criticism, as the Chile, California and Washington sites have done, he worked to deduce the age more precisely and with certainty. They dug a ditch at the site, leaving layers of rocks several feet down. Six of those layers had footprints. The deepest of them – thus the oldest – lies under a layer of seed they dated 22,800 years ago.

Thus the footprints are at least 22,800 years old. Almost the same analysis showed that the youngest of the footprints is about 21,000 years old. Overall, much older than Clovis’ tools; Long before the retreat of the continent-wide expansion of glaciers at the end of the Ice Age.

So if this finding holds up, the immediate question is, how did these ancient humans get to New Mexico? Their ancestors most likely crossed into Alaska on a “land bridge” that later submerged as the ice sheets melted. If you look at a map, you can see the wreckage of this bridge: a chain of small islands stretching between Siberia and Alaska, today separated by long stretches of the Bering Sea. But after all those millennia ago, ancient humans were confined to Alaska by the glaciers that covered the rest of North America, and did not melt for many more years. millennium. It is hardly possible that they walked thousands of miles of ice to New Mexico. So how did they get there?

One theory is that they traveled south in small boats, along the Pacific coast of North America. At some point, perhaps in California today, the snow cover ceased. There, more than likely sick of sailing, these ancestors of ours came ashore, abandoned their boats, and went inland. stable inland. There is probably white sand a thousand miles east. When they got there, they saw a lake with moat grass and other plants on the shore, wandering sloths and other potential prey. Pleasant location, no doubt about it. So maybe they decided to stay for a while. His children gambled like children do, chasing down the slothful or at any rate following in his footsteps.

And they left tracks in the sand. 23,000 years later, some curious archaeologists discovered the tracks and learned about these early humans.

Dilip D’Souza, once a computer scientist, now lives in Mumbai and writes for his dinner. His Twitter handle is @DeathEndsFun