Mexican cave relics suggest humans were populating the Americas up to 17,000 years earlier than thought Humans are likely to have occupied the Americas from 30,000 years ago, which is much earlier than previously thought. Stone tool found above the Last Glacial Maximum (LGM) layer, within Stratigraphic Component B. This particular piece was made from a greenish crystallized limestone. Credit: Ciprian Ardelean. Stone tool found …
I was under the impression that the Overkill theory was losing ground to the Younger Dryas Impact theory which blames a series of airburst meteors over the Americas around the 10,900 BP mark that put paid to much of the Mega Fauna so the appearance of these folk as many as 16,000 years earlier is hardly a case of overkill, unless they were having a population explosion after several milennia.
There are a number of ideas about the causes of the last extinction's causes. One of the rather poorly considered aspects of the extinction is that it was not sudden at all. Cave bears in Europe for instance pretty much were gone by the glacial maximum. Other extinctions waited until the Holocene was well underway. Some ecological communities such as the mammoth steppe completely vanished - that is an entire habitat type that no longer exists. The best explanation is that a number of circumstances came together in a perfect storm of events. One of the aspects of the Y-D period is that it marks the end of Clovis, so any list of extinctions correlated with the Y-D should include Clovis as an extinction. I think that there were demonstrably several "suboptimal" conditions. One is that as the last glacial developed, primary productivity declined globally. There was both cold-associated drought and a seriously low level of CO2, very close to levels where primary production just shuts down. There was the abrupt climatic shift as the glacial ended, mark a period of very rapid warming and quickly shifting environmental communities. Then there was the Y-D, part way through the warming that complete reversed climate trends for around a millennium. At the same time something extraterrestrial happen as well. There is a problem with radio carbon dating that seems to collapse the Y-D into a span much shorter than it was in reality. That suggests an influx of cosmic rays adequate to significantly enrich C-14 in the atmosphere. For the Americas, the end of the Pliestocene also marks the end of geographic isolation and that may very well have lead to the epidemic spread of disease among many genera including possibly, paleoindians.
I don't get all the downvotes. It's always been confusing to me why evidence of settlements predating Clovis were so fiercely disregarded or invalidated. It comes across as dogma. I associate it with a white male approach to archaeology. Especially the disbelief that people could have arrived prehistorically by sea instead of land.
People don’t like to be wrong. When you have published a slew of papers, books, given public talks, taught a couple of generations of students to be told it was all wrong is hard to take. It’s the sunk cost fallacy us humans are very prone to. Us scientists are humans with careers and reputations and too often that trumps the science.
But the data will continue to come. They tried to get dna from the bones and layers but failed. But there will be a cave out there in the Americas with pre Clovis dna in it I’’m sure.
Considering Australia was reached 50-60kya the much later date for the Americas is curious. We know people made dugout canoes, maybe lashed them together to make catamaran paddled rafts. That gets you around the coasts in Beringia and you follow it down until there’s enough ice free land you can walk inland.
There may have been founder effects with genetic isolation. We’re a very inbred species to start with. Doesn’t take long for the recessive genes to start to come out. Maybe they died out, maybe Clovis supplanted them with better tech. Or maybe the disease burden of Clovis did for them.
Trading up the Amazon killed the great jungle civilisations when Europeans were only on the coasts. By the time Europeans got into the interior the jungle had grown over the cities. It took Lidar and ground penetrating radar to reveal the cities and the remains of the field systems.
Obsidian which can be fingerprinted to individual volcanoes has been used to prove long range inter island trade in the Pacific. For several generations after settlement the people of Aotearoa were trading with the homeland (Tahitii, Mangareva, Tuamotus). Us humans will trade.
One fun little details is that you can draw a line of longitude around the earth, up the coast of chile and the eastern united states, over the arctic and down across china to australia, and find devastation and megafuna extinctions everywhere you look in a broad swathe either side of it. Australia is scarred by impact sits similar to the elongated cratering and soot layer that marks the boundary of the clovis artefacts, but it doesn't really appear elsewhere in the world. Megafauna in the Americas - particular South America - was driven to extinction, as was megafuna in east asia and australasia, whilst megafauna in central and southern asia, africa and - to a lesser extent - europe were left intact.
There's no generally accepted hypothesis for why this would be so, but it's an interesting detail.
Australian aboriginal myths tell of a day of great devastation, of fire from the sky and great floods, that could possibly be associated with known tsunami and unusual crater-like formations on Australia's south coast.
It might be possible that some impactor sung around the earth at close to 90 degrees to the equator, broke up as it did so, and dropped a bunch of meteorites along that path.
Maybe.
Not necessarily, and frankly the fact that there were older human populations there also doesnt kill the human based megafauna extinction option. Just consider different groups had different hunting/gathering methods.
As a good example, the very first Australian Aborigines lived alongside Australian megafauna (think massive Wombats and kangaroos!), but at some point the Aborigines discovered the hunting technique of setting an area on fire and using that to drive the animals to their hunting areas. The fires affected what grew in Australia, leaving only fire hardened trees and plants, and thus removing the vital ecosystem that supported the Megafauna.
It's not necessary to physically kill off every last creature, affecting the environment to such an extent will have the same effect. Who knows, maybe those pre-Clovis civilisations had a minimal effect on their local environment and so lived alongside the American megafauna, whereas the Clovis changed things and brought about the end of the Megafauna.
As always, more great science like the research in this article will help us understand our history... :)
Definitely, the Younger Dryas impact (probably in Greenland) looks like it may have removed not only the mega fauna but also virtually all the evidence of human occupation in North America, washing most of it away. When you look at the genetics of humans today it seems quite possible that humans have been floating around the world for at least 100,000 years - something that western culture denies could of happened because there's no (white) evidence of it; but genetics suggests that humans were not just isolated in little groups throughout history.
Of course it's all just guesswork, there are no posts on Facebook, Instagram or Twitter back then, all we have is pictures on cave walls.
... but it's becoming less guesswork with each artifact that is unearthed and dated. Nice to see science at work.
And, BTW, it's not "accelerated mass spectrometry", but accellerator mass spectrometry. The carbon atoms are accelerated through a thin foil to strip all their electrons -- so the nuclear mass can be reliably measured. It's a famously tedious experiment to perform because you need to count a few 14-C atoms amongst trillions of other carbon atoms. You really can't accelerate that, you have to bring some patience and continue counting for a while.
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