Study casts doubt on mammoth-killing cosmic impact

Study casts doubt on mammoth-killing cosmic impact
The Younger Dryas, the period being studied by UC Davis and other earth scientists, coincided with the extinction of mammoths and other great beasts and the disappearance of the Paleo-Indian Clovis people. Credit: Thinkstock

Rock soil droplets formed by heating most likely came from Stone Age house fires and not from a disastrous cosmic impact 12,900 years ago, according to new research from the University of California, Davis. The study, of soil from Syria, is the latest to discredit the controversial theory that a cosmic impact triggered the Younger Dryas cold period.

The Younger Dryas lasted a thousand years and coincided with the extinction of mammoths and other great beasts and the disappearance of the Paleo-Indian Clovis people. In the 1980s, some researchers put forward the idea that the cool period, which fell between two major glaciations, began when a comet or meteorite struck North America.

In the new study, published online in the Journal of Archaeological Science, scientists analyzed siliceous scoria —porous granules associated with melting—from four sites in northern Syria dating back 10,000 to 13,000 years ago. They compared them to similar scoria droplets previously suggested to be the result of a cosmic impact at the onset of the Younger Dryas.

"For the Syria side, the impact theory is out," said lead author Peter Thy, a project scientist in the UC Davis Department of Earth and Planetary Sciences. "There's no way that can be done."

The findings supporting that conclusion include:

  • The composition of the scoria droplets was related to the local , not to soil from other continents, as one would expect from an intercontinental impact.
  • The texture of the droplets, thermodynamic modeling and other analyses showed the droplets were formed by short-lived heating events of modest temperatures, and not by the intense, high temperatures expected from a large impact event.
  • And in a key finding, the samples collected from archaeological sites spanned 3,000 years. "If there was one cosmic impact," Thy said, "they should be connected by one date and not a period of 3,000 years."

So if not resulting from a , where did the scoria droplets come from? House fires. The study area of Syria was associated with early agricultural settlements along the Euphrates River. Most of the locations include mud-brick structures, some of which show signs of intense fire and melting. The study concludes that the scoria formed when fires ripped through buildings made of a mix of local soil and straw.

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More information: Journal of Archaeological Science, … ii/S0305440314004403
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Jan 06, 2015
This 'impact' idea is still out and get clobbered when it meets reality (more careful researchers). But it is a new year, and we can expect the 'impact' researchers try their bad science again. Sigh.

"And in a key finding, the samples collected from archaeological sites spanned 3,000 years."

Ouch! Speak of getting their pants pulled down.

How could the impacteers even miss that/fantasize that it was a small enough span?

Jan 06, 2015
Milankovich cycles. The last Ice Age corresponded with a time when the North Pole was tilted away from the sun at aphelion, resulting in VERY cold winters and heavy ice accumulations and increased albedo - enough to make the ice last all summer.

Jan 06, 2015
I'm still toying with a thought of massive methane release and ignition...

Jan 06, 2015
I've not looked into this whole controversy beyond what findings have been published here on physorg, but, it seems to me that the claims of an impact event where based upon the presence of supposedly impact-generated nanodiamonds.

So, it would appear that these scoria droplets don't meet the standard necessary to invalidate the impact hypothesis.

A couple other things to take into account would be the fact that Syria is at a considerably lower lattitide than those in which this impact was supposed to have occurred, not to mention upon a different continent.

Also, it escapes me just how these scoria droplets could be meaningfully separated from those produced by entirely natural means(wildfires) or from even more distant sites of human activity

I don't mean to say that I support the impact theory --it's just that I don't quite see how this can be said to shut the door...definitively or no.

Jan 07, 2015
@Caliban: It is a fringe idea, that is futilely but embarrassingly pursued. Paleonthologists, geologists et cetera are getting tired about having to show how these guys mess up.

"According to the researchers, the Younger Dryas impact event evidence "fails the critical chronological test of an isochronous event at the YD onset, which, coupled with the many published concerns about the extraterrestrial origin of the purported impact markers, renders the YDIH unsupported. There is no reason or compelling evidence to accept the claim that a cosmic impact occurred ∼12,800 y ago and caused the Younger Dryas."[48]"

[ http://en.wikiped...pothesis ]

It isn't a case of closing a door, it is a case of a pseudoscience group that can't open a door. Presumably because it doesn't exist, but after all this ruckus who cares? It is bullshit.

Jan 07, 2015
That's an interesting comment Torbjorn_Larsson_OM, and it seems to me we started a very similar discussion on another article in at PO that was discussing findings that supported the impact theory.

You're pretty big on disparaging the scientists who are working on that theory, and I have yet to see much beyond rhetoric from you on the subject. Do you recall this article?

You never did respond to my comments. It would seem now that you suport some other mechanism besides impact as the cause of the YD event. So, what theory do you feel has more support? And why?

Jan 09, 2015
Something happened 12,000 years ago which caused a sharp cooling of climate for a 1000 years. Contemporaneously, in the northern hemisphere most of the megafauna died off--including whoever made the clovis points We call this period the younger dryas. Why did the sharp counter trend in temperature occur? Did this result in a cascade of events that caused the megafauna to die? Mere cold would not have done it--since the megafauna had experienced many 1000's of years of cold before without going extinct.

Currently there are a lot of theories as to why this happened. The most popular are human hunters killing the megafauna and the comet strike or some combination of the two. All of them sound plausible. None are proved.

Jan 09, 2015
@ hopper - there are a number of other theories that have some traction. The most popular one is the sudden emptying of glacial Lake Aggassiz, resulting is a rapid desalination of the Arctic ocean and a corresponding loss of, or sharply reduced, ocean circulation. Other theories suggest a less dramatic freshening of the ocean, a change in atmospheric circulation, especially the polar jet stream, a sudden reduction in solar energy, or even a large solar flare event.

The two theories which seem to have the most support are the impact theory and the sudden draining of Agassiz. Those are often combined with the idea that the die off may have been hastened or pushed over the edge by human hunting.

It is an interesting subject, and both sides have some compelling arguments.

Jan 13, 2015
I came across a blog article written by Steven Novella discussing this very debate. I find it compelling because I think it sets out the differing aspects of the two main competing theories quite well. For anyone interested, his comments are here:

This, in my mind, describes accurately the difference between scientific debate and the dogmatic adherence to a position. See what I am driving at Torbjorn?

Jan 17, 2015
I would like to throw out the pathogen theory as well right here, right now. If you proposed this theory at a conference with a virologist or any serious microbiologist in the audience he would double up with laughter and so would I. Just the idea that all the megafauna are suddenly stricken with a mystery illness that affects a broad base of diverse species within the megafauna category on both continents yet sparing most if not all the smaller fauna including man during the late Pleistocene is well beyond credulity and common sense. There has never been any pathogen identified that would be capable of causing such an extinction event. NO EVIDENCE

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