Skip to comments.Comet theory false; doesn't explain Ice Age cold snap, Clovis changes, animal extinction
Posted on 05/17/2014 12:06:11 PM PDT by Renfield
Controversy over what sparked the Younger Dryas, a brief return to near glacial conditions at the end of the Ice Age, includes a theory that it was caused by a comet hitting the Earth.
As proof, proponents point to sediments containing deposits they believe could result only from a cosmic impact.
Now a new study disproves that theory, said archaeologist David Meltzer, Southern Methodist University, Dallas. Meltzer is lead author on the study and an expert in the Clovis culture, the peoples who lived in North America at the end of the Ice Age.
Meltzer's research team found that nearly all sediment layers purported to be from the Ice Age at 29 sites in North America and on three other continents are actually either much younger or much older.
Scientists agree that the brief episode at the end of the Ice Age officially known as the Younger Dryas for a flower that flourished at that time sparked widespread cooling of the Earth 12,800 years ago and that this cool period lasted for 1,000 years. But theories about the cause of this abrupt climate change are numerous. They range from changes in ocean circulation patterns caused by glacial meltwater entering the ocean to the cosmic-impact theory.
The cosmic-impact theory is said to be supported by the presence of geological indicators that are extraterrestrial in origin. However a review of the dating of the sediments at the 29 sites reported to have such indicators proves the cosmic-impact theory false, said Meltzer.
Meltzer and his co-authors found that only three of 29 sites commonly referenced to support the cosmic-impact theory actually date to the window of time for the Ice Age.
The findings, "Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago," were reported May 12, 2014, in the Proceedings of the National Academy of Sciences.
Co-authors were Vance T. Holliday and D. Shane Miller, both from the University of Arizona; and Michael D. Cannon, SWCA Environmental Consultants Inc., Salt Lake City, Utah.
"The supposed impact markers are undated or significantly older or younger than 12,800 years ago," report the authors. "Either there were many more impacts than supposed, including one as recently as 5 centuries ago, or, far more likely, these are not extraterrestrial impact markers."
Dating of purported Younger Dryas sites proves unreliable
The Younger Dryas Impact Hypothesis rests heavily on the claim that there is a Younger Dryas boundary layer at 29 sites in the Americas and elsewhere that contains deposits of supposed extraterrestrial origin that date to a 300-year span centered on 12,800 years ago.
The deposits include magnetic grains with iridium, magnetic microspherules, charcoal, soot, carbon spherules, glass-like carbon containing nanodiamonds, and fullerenes with extraterrestrial helium, all said to result from a comet or other cosmic event hitting the Earth.
Meltzer and his colleagues tested that hypothesis by investigating the existing stratigraphic and chronological data sets reported in the published scientific literature and accepted as proof by cosmic-impact proponents, to determine if these markers dated to the onset of the Younger Dryas.
They sorted the 29 sites by the availability of radiometric or numeric ages and then the type of age control, if available, and whether the age control is secure.
The researchers found that three sites lack absolute age control: at Chobot, Alberta, the three Clovis points found lack stratigraphic context, and the majority of other diagnostic artifacts are younger than Clovis by thousands of years; at Morley, Alberta, ridges are assumed without evidence to be chronologically correlated with Ice Age hills 2,600 kilometers away; and at Paw Paw Cove, Maryland, horizontal integrity of the Clovis artifacts found is compromised, according to that site's principal archaeologist.
The remaining 26 sites have radiometric or other potential numeric ages, but only three date to the Younger Dryas boundary layer.
At eight of those sites, the ages are unrelated to the supposed Younger Dryas boundary layer, as for example at Gainey, Michigan, where extensive stratigraphic mixing of artifacts found at the site makes it impossible to know their position to the supposed Younger Dryas boundary layer. Where direct dating did occur, it's sometime after the 16th century A.D.
At Wally's Beach, Alberta, a radiocarbon age of 10,980 purportedly dates extraterrestrial impact markers from sediment in the skull of an extinct horse. In actuality, the date is from an extinct musk ox, and the fossil yielding the supposed impact markers was not dated, nor is there evidence to suggest that the fossils from Wally's Beach are all of the same age or date to the Younger Dryas onset.
At nearly a dozen other sites, the authors report, the chronological results are neither reliable nor valid as a result of significant statistical flaws in the analysis, the omission of ages from the models, and the disregard of statistical uncertainty that accompanies all radiometric dates.
For example, at Lake Cuitzeo, Mexico, Meltzer and his team used the data of previous researchers and applied a fifth-order polynomial regression, but it returned a different equation that put the cosmic-impact markers at a depth well above that which would mark the Younger Dryas onset.
The authors go on to point out that inferences about the ages of supposed Younger Dryas boundary layers are unsupported by replication in more cases than not.
In North America, the Ice Age was marked by the mass extinction of several dozen genera of large mammals, including mammoths, mastodons, American horses, Western camels, two types of deer, ancient bison, giant beaver, giant bears, sabre-toothed cats, giant bears, American cheetahs, and many other animals, as well as plants.
This goes against the consensus, it must be wrong...
So, I guess under modern climatology standards, these renegade scientists would be called Comet Climate Change deniers.
Oh, heaven NO!!!!!
A global climate change event in recent human history both unexplained and unable to be attached to human activities.
OH THE HORROR!!
(the sun can’t possibly have anything to do with it, of course)
Ancient Astronaut Theorists believe......
I always thought the global warming was caused by Fred Flintstone and Barney Rubble and their friends.
“changes in ocean circulation patterns caused by glacial meltwater entering the ocean”
In view of the dramatic meltwater created Washington Scablands, and other rapid release of meltwater like Hudson Bay, I’ll stick with temporary ocean current disruption.
Controversy over what sparked the Younger Dryas, a brief return to near glacial conditions at the end of the Ice Age, includes a theory that it was caused by a comet hitting the Earth.Huh? Correct me if I'm wrong, but that's not in the book I read. Straw Man Alert!
The Cycle of Cosmic Catastrophes:
Flood, Fire, and Famine
in the History of Civilization
by Richard Firestone,
Allen West, and
[snip] The following ran in the Feb. 29, 2012, edition of the Washington Post. Anthropol[og]ist David Meltzer provided expertise for this story.
Radical theory of first Americans places Stone Age Europeans in Delmarva 20,000 years ago
March 9, 2012
By Brian Vastag
For quite a while the consensus theory was that this extinction was caused by human hunters.
I used to be quite resistant to this notion, as it just seem unlikely to me that human stone age hunters could exterminate so many animal across an entire continent in just a few centuries.
However, we have good the same thing happened in Australia, New Zealand, Madagascar and other islands. The mega-fauna disappeared within a couple of centuries of humans showing up.
So I'm a somewhat reluctant convert.
Why didn’t the mega fauna of Asia and Africa die out as well? I would have loved to see that huge armadillo cousin Glyptodont with its mace like tail walking near a stream during the last ice age.
The theory, which I don’t find entirely convincing, is that African, and to a lesser extent Asian, megafauna were around when humans evolved and had time to learn to adapt to them.
In the Americas, Oz and elsewhere the animals weren’t adapted to this uniquely effective predator and were wiped out by us.
Just curious, but how much have you actually looked into the distribution of massive accumulations of megafauna remains and other detritus deposited at or near the end of the last glaciation in North America and elsewhere?
In any case, for me, the "hunted to extinction" narrative has a "man made global warming" ring to it.
This is an excellent book. I was convinced by it, and remain convinced. The authors showed the debris impact radiating through the U.S. through the existence of ponds that look like a sunburst....as I recall, as far away as North Carolina.
I hear there are still Rodents Of Unusual Size (ROUS).
The “hunted to extinction” theory is actually one of those neat theories that causes cognitive dissonance in PC-people.
It’s PC because it means Man is Evil. Look at how We wiped out so many wonderful creatures! This is the echo of global warming you hear. (Which does not of itself mean it isn’t true.)
OTOH, it would mean the ancestors of today’s Native Americans are the ones who did the wiping out. Which is obviously very much non-PC. There is immense irony in this, if true, because the extinction of the horse (and other potentially domesticable animals) in the Americas was a major contributor to their inability to effectively resist European invasion.
So I enjoy the Progressive types trying to figure out which implication of the “wiped-out” theory should take precedence on the PC-scale.
There are some problems with this mass extinction. The notion that it was entirely non-human related is made a good deal less likely by the fact that many of these animals had survived other cycles of glaciation and ends of the glaciation. Why did this particular one cause the extinction of so many species?
OTOH, the “wipe them out” theory is made less likely because it’s based on the notion that humans first hit the Americas about 12,000 years ago. There is increasing, though not yet really conclusive, evidence that humans have been around here perhaps twice that long. Which would mean that humans lived alongside the megafauna without wiping them out for 10,000 or 12,000 years.
I also find the sheer mechanics of the wipe-out improbable. How many stone-age hunters would it take to cause an extermination across two entire continents? Seems to me it would take many millions, and there just really isn’t evidence of that massive a population being around.
Americans wiped out the buffalo in less than a decade, but we had breech-loading rifles accurate at hundreds of yards. How long would it have taken with spears or even bows?
OTOH, there is that “coincidence” of similar mass extinctions within a century or two of humans reaching multiple other landmasses.
So I think the theory of wipe out is possible, but not conclusively proven.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.