About 12,800 years ago, the last Ice Age was coming to an end, the planet was warming up. Then, inexplicably, the planet plunged into a deep freeze, returning to near-glacial temperatures for more than a millennium before getting warm again. The mammoths disappeared at about the same time, as did some Native American cultures that thrived on hunting them. That climatic event is known as The Younger Dryas.
Many explanations for the event point to the impact of a comet or an asteroid, but now there is a new study suggests the driver/trigger was all from terrestrial based events.”
According to the article in Science Magazine, they find no evidence for an impact:
The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.”
The notion was popularized in television documentaries and other coverage on the National Geographic Channel, History Channel, and the PBS program NOVA.
…
Now comes what some researchers consider the strongest attack yet on the Younger Dryas impact hypothesis. In a paper published online this week in the Proceedings of the National Academy of Sciences, a team led by David Meltzer, an archaeologist at Southern Methodist University, Dallas, in Texas, looks at the dating of 29 different sites in the Americas, Europe, and the Middle East in which impact advocates have reported evidence for a cosmic collision.
Only three of the 29 sites actually fall within the time frame of the Younger Dryas onset
http://news.sciencemag.org/archaeology/2014/05/what-caused-1300-year-deep-freeze
From the publication:
A key element underpinning the controversial hypothesis of a widely destructive extraterrestrial impact at the onset of the Younger Dryas is the claim that 29 sites across four continents yield impact indicators all dated to 12,800 ± 150 years ago. This claim can be rejected: only three of those sites are dated to this window of time. At the remainder, the supposed impact markers are undated or significantly older or younger than 12,800 years ago. 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.
Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago
David J. Meltzer, doi: 10.1073/pnas.1401150111
David J. Meltzera, Vance T. Holliday, Michael D. Cannon, and D. Shane Miller
Abstract
According to the Younger Dryas Impact Hypothesis (YDIH), ∼12,800 calendar years before present, North America experienced an extraterrestrial impact that triggered the Younger Dryas and devastated human populations and biotic communities on this continent and elsewhere. This supposed event is reportedly marked by multiple impact indicators, but critics have challenged this evidence, and considerable controversy now surrounds the YDIH. Proponents of the YDIH state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the Younger Dryas onset. They are not. We have examined the age basis of the supposed Younger Dryas boundary layer at the 29 sites and regions in North and South America, Europe, and the Middle East in which proponents report its occurrence. Several of the sites lack any age control, others have radiometric ages that are chronologically irrelevant, nearly a dozen have ages inferred by statistically and chronologically flawed age–depth interpolations, and in several the ages directly on the supposed impact layer are older or younger than ∼12,800 calendar years ago. Only 3 of the 29 sites fall within the temporal window of the YD onset as defined by YDIH proponents. The YDIH 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.
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@Em SMkith –
“The idea that humans hunted ALL the megafauna of North America to extinction at exactly the same time is simply stupid. There just were not enough humans to do that.”
DUH.
You might be interested in my Sunday blog post at http://feet2thefire.wordpress.com/2014/05/10/mapping-clovis-man-vs-mammoths-just-asking/
Discussing the fact that most Clovis points are NOT found out west. The VAST majority are in the EAST. And the highest concentrations are where NO mammoths have ever been found. Obviously the Clovis people were eating something THERE other than mammoths.
It Boggles my mind that anyone could think such a stupid thing – that Clovis would hunt a 5,000 lb mammoth, which has about 3,000 lbs of meat AS THEIR MAIN SOURCE OF MEAT. HOW in the wworld could they keep it from spoiling? Drying racks? Do they have any IDEA how many drying racks it would take? And how could they haul that much meat back to their families? And WHY? When there are many kinds of smaller game to hunt, that are much less dangerous and do not take a factory-sized effort to cure and then pack up and haul?
Add to that that the great number od Clovis people were east of the MIssissippi, and what are we talking here – hunting expeditions 1,000 to 2,000 miles away? And hauling that much meat back THAT far?
Whatever those arkies and paleos are smoking, I don’t want any of it. Let them Bogart that joint, my friend.
One site has over 12 mammoth skeletons. That is about 40,000 lbs of meat. At 1/2 lb of meat per serving, that is 80,000 meals.
mikewaite says:
May 13, 2014 at 12:42 pm
Gone with onset of CACA grant money.
Many consider it no accident that the Dark Ages folk migrations, aka barbarian invasions, coincide with the deterioration of climate from the Roman Warm Period to colder prevailing conditions. Then during the Medieval Warm Period, the barbarians settled down, becoming Christian farmers rather than pagan pirates & raiders.
During the High Middle Ages, population grew, horses were bred larger thanks to abundant fodder & armor got heavier on both knights & their mounts. Then from around AD 1250, things started deteriorating again, but worsened in the early 1300s. Then from the 1340s came famine, war & pestilence, carrying off perhaps 60% of Europe’s population. Maybe more. The Little Ice Age bottomed out around 1700, but persisted in reduced form until about 1850.
@Hell_Is_Like_Newark at 5:10 am:
“Some things that happened during the Younger-Dryas:
1. It got colder yet sea level continued to rise dramatically.
2. Melt-water from the Laurentide ice sheet switched from flowing South into the Gulf of Mexico suddenly shifted to dumping into the North Atlantic.
3. The Clovis culture and large land mammals pretty much disappeared in the fossil record. There is a mysterious black mat above which mega-fauna and the Clovis no longer exist.”
1. Yes, correct.
3. Yes, correct.
As to 2. No. Yes, the outflow to the Gulf of Mexico changed. NO, to the shift to the Atlantic. The originator of that idea, Wally Broeker, even gave up on that idea. The timing of the retreat of the Laurentide simply was too late. The serachd for outlet for the ice dam failure on Lake Agassiz had to be aborted. The timing killed the idea, and Wally accepts that.
Since that became patently clear, the idea floundered, but then the proponents have shifted to an outlet via the Mackenzie River north, across the Yukon, to the western Arctic – about as FAR away from the Atlantic as you can get in Canada – like 4,000 miles away, and past many islands, including the big one, Greenland. On a DUMBEST IDEA OF THE 21st CENTURY scale, that one is about a 12 on a 10-point scale. But they are running with it.
Seriously stupid idea. Why not have it flow WEST, over the Rockies? It is just about that dumb. Or through some imaginary underground river to come up right by Iceland?
In any event, the St Lawrence outlet for Lake Agassiz failed. Oh, it might have succeeded if it didn’t have to be right THEN. (But no Scablands-like scour has ever been found south of Lake Agassiz, so no, it still fails.)
Steve Garcia says:
May 13, 2014 at 12:57 pm
There were mammoths in the US SE (such as Florida) & indeed Mexico. North America was home to other mammoths besides woollies, like the giant Imperial & Columbian species or subspecies. Plus of course North & South American mastodons & gomphotheres, proboscideans not members of the elephant family.
http://news.discovery.com/human/evolution/early-man-florida-120509.htm
But the Overkill Hypothesis doesn’t argue that Clovis hunters killed only mammoths. Quite the contrary. And surely a lot of meat was wasted. That’s sort of the point.
I keep telling the CAGWers that if they really want to worry about something climate-related, they should focus on the overdue transition out of the current interglacial, which is far more likely to end human civilization than any putative future warming.
But you can’t blame the evils of modern industry, so no go.
@John Slayton at 6:35 am:
“Could someone with access, bring back the names of those three sites?”
How about this:
From Wiki:
“The San Pedro River Valley is rich in discovered Clovis culture sites. Within a 50-mile radius are nearly a dozen Clovis sites including the Lehrner Mammoth Kill Site, the Naco Mammoth Kill Site, the Escapule Clovis Site and the Leikem Clovis Site.”
“If I remember correctly, the Murray Springs black mat layer (with alleged nano-diamonds) was correlated with other sites some distance away–like thousands of miles. One suggestion was that there may have never been an actual impact, only a disintegration causing huge damage along the object’s trajectory. Seems to this layman that 3 well-dated sites that far apart showing (if true) identical geological anomalies, is significant evidence for impact, even if all the others are irrelevant.”
Exactly.
As I’ve pointed out here (and elsewhere), there is a small cadre of YDB skeptics that I call “The Daulton Gang” – mainstreamers all, which means they have invested their careers in other mammoth extinction hypotheses, and have a vested interest in poking holes in the evidence you have read about. That cadre does NOT do any original work – no field work, no sampling, no NOTHING. All they do is write up “Op-Ed” pieces that the journals keep on publishing. Because the journals themselves are fully vested in a non-catastrophic naturla history of Earth.
Actually, one of them DID go out to get samples (Surovell 2009). But he was out of his element and he screwed it up – totally did not sample correctly. He mixed in samples of FAR too wide a time range, which resulted in watered-down samples. HE didn’t follow the sampling protocol. And he also didn’t even ask someone else what to do, so he did it wrong. THEN he published. And THEN the pro-YDB folks ripped him a new anus. He hasn’t been back to either rebut or to do new sampling. He didn’t even DEFEND his work.
BTW, the pro-impact evidence now extends to FOUR continents.
Re the Overkill hypothesis — this has way too much explanatory power to be dismissed on those grounds. It’s entirely possible for bands of early humans to hunt everything in an area to extinction within months of their arrival — that’s why you don’t see settlement remains in the fossil record next to large animal extinctions, they never had a chance to settle!
It Boggles my mind that anyone could think such a stupid thing – that Clovis would hunt a 5,000 lb mammoth, which has about 3,000 lbs of meat AS THEIR MAIN SOURCE OF MEAT.HOW in the wworld could they keep it from spoiling?
Clovis Hunter 1: “Hey, look at that thing. It has so much meat on it, we have no idea how to preserve it!”
Clovis Hunter 2: “Yeah, good point. Let’s continue to nearly starve instead.”
And WHY? When there are many kinds of smaller game to hunt, that are much less dangerous and do not take a factory-sized effort to cure and then pack up and haul?
Could not be more wrong. Humans can set gravity traps for large prey. Big dumb animals have a much better reward/effort ratio than little clever animals.
talldave2 says:
May 13, 2014 at 1:24 pm
End of the Holocene isn’t overdue, although temperature trend has been down for at least 3000 years. The Eemian lasted about 5000 years longer than the Holocene has to date, while MIS 11 lasted tens of thousands of years longer. Interglacials vary a lot in duration.
Depending upon which orbital parameter dominates, the Holocene could last a lot longer. Or not. Interglacials are all different in details, but there does appear to be a ~400,000 year pattern, ie a super interglacial every fourth glacial/interglacial cycle.
The issue of when the Holocene might end & whether its demise is overdue has been discussed a lot on this blog.
http://www.clim-past.net/8/1473/2012/cp-8-1473-2012.html
Forgive the authors’ mention of CO2, which in this case is a proxy for temperature, since higher T means higher T, not necessarily the other way around.
talldave2 says:
May 13, 2014 at 1:28 pm
You’re right, IMO. Humans have repeatedly been shown capable of hunting naive species to extinction, even on continental scales, not just islands.
The Overkill Hypothesis isn’t mutually exclusive with an impact hypothesis, however, IMO. But fluctuations in deglaciation similar to the Dryas Events have been observed in previous Pleistocene glacial/interglacial transitions. Maybe Earth enters cometary or asteroidal debris zones periodically, but IMO there are better explanations. However if convincing physical evidence emerges for a YD impact or series of hits, then I’m willing to entertain that possibility.
I thought the prevailing theory for the Younger Dryas was the opening of the outlet from the Great Lakes to the North Atlantic releasing a lot of dammed up meltwater barely above freezing disrupting the Gulf Stream.
milodonharlani says:
May 13, 2014 at 10:45 am
………..
Thanks, I was speaking in more general terms, I am aware of the periodic variability in the Ice ages cycles. I suspect there may be more to the Milankovic cycles than just the earth’s axis inclination.
Milankovic cycles may have something with the SSN, the Arctic tectonics and the N. Atlantic temperatures. My limited collection of integrated tectonics data for the region, compares ‘well’ with the sunspot cycles, considering what two sets of data represent.
When I chop the data and compare to the NA SST (AMO), an even ‘better’ agreement is reached.
http://www.vukcevic.talktalk.net/SNAt.htm
pseudo-science at its best (or its worst according to Dr. S); perhaps more next time.
The Monster (@SumErgoMonstro) says:
May 13, 2014 at 1:52 pm
That is the prevailing theory, but geological evidence for it is weak. I find it plausible, however alternative hypotheses, besides the impact theory, compete with it.
One suggests that the jet stream shifted northward in response to the changing topography of a melting Laurentide Ice Sheet, bringing more rain to the North Atlantic, freshening the ocean surface enough to slow thermohaline circulation.
Some evidence also exists that a solar flare might have caused or contributed to extinction of the megafauna, although this can’t explain apparent variability in the extinctions among continents.
The freshwater lid from glacial melting hypothesis is IMO supported by similar observations in at least the prior deglaciation, if not previous ones.
Dennis Cox, [May 13, 2014 at 8:52 am]
First of all, I thoroughly enjoyed reading your ideas (A Different Kind of Climate Catastrophe [2011/04/06]) usefully linked to above by hell_is_like_newark, for which, both of you: thank you very much indeed. It would thrill me no end to have it established that you are on the right track.
By the way, I subsequently discovered that you have what seems to be another (updated/revised?) version which I haven’t had time to look at yet: A Different Kind of Climate Catastrophe (2) [2011/04/27]. Could you briefly outline its status, please?
I’m a complete layman as far as geology is concerned but the way you put all that together looked eminently convincing to me. Your openness shone through too — you score big brownie points on that one. 🙂
Could you kindly outline the subsequent reception of your ideas? You alluded to upcoming or in-progress studies by others. Have these seen fruit yet? Your paper is now three years old, so I’m hoping some progress has been made.
I like your style very much. 🙂
Best wishes,
John Archer
P.S. I’m posting this before having read all the comments here—of which there are quite a few—so I may have missed some relevant responses. Put it down to my ungovernable urge for immediate gratification. 🙂
talldave2 says:
May 13, 2014 at 1:34 pm
Could not be more wrong. Humans can set gravity traps for large prey. Big dumb animals have a much better reward/effort ratio than little clever animals.
==========================================================
20 hunters carrying 100 lbs each back to camp to smoke and make jerky. The left behinds wouldn’t matter. If camp was close by, they go back and get it. As Yuka looked, the hunter(s) took the choice cuts and let the wolves have the rest. Smaller hunting bands would leave more, but no big deal; go kill another one. I doubt the Plains Indians had a preset limit on how many Bison they took.
The bipolar seesaw – reciprocal interhemispheric temperature oscillation mediated by deep ocean circulation and heat piracy, caused the Bolling-Allerod and Younger Dryas:
http://onlinelibrary.wiley.com/doi/10.1029/97PA03707/pdf
http://www.researchgate.net/publication/227653604_Atlantic_ocean_heat_piracy_and_the_bipolar_climate_seesaw_during_Heinrich_and_DansgaardOeschger_events/file/3deec5256d0f01a679.pdf
http://onlinelibrary.wiley.com/doi/10.1029/2003PA000920/pdf
http://onlinelibrary.wiley.com/doi/10.1029/97GL02658/pdf
etc…
James the Elder says:
May 13, 2014 at 3:36 pm
Archaic (or possibly Paleo-Indian, who might not have been “Indians”) people, possibly ancestors of some present American Indian groups, stampeded Bison antiquus over cliffs c. 8000 BC, as historical Plains Indians did with Bison bison.
jim2 says:
May 13, 2014 at 9:31 am
Maybe it could have been the Vela supernova, a relatively close explosion at 800 lightyears.
The resulting cosmic rays could have enhanced clouds and cooled the Earth.
Vela Supernova Remnant.jpg Vela Supernova 11th–9th millennium BCE ? 800 ? Vela Supernova Remnant
http://en.wikipedia.org/wiki/List_of_supernova_remnants
————————————————————————–
My thoughts too..a nova wave..
http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.html
The graph above looks like the foreshock wave was dense cloud, main shockwave piece hot and the aftershock wave dense cloud.
vukcevic says:
May 13, 2014 at 2:10 pm
Of course Milankovitch cycles have to do with more than just the earth’s axial tilt, which is of lesser importance than some other orbital mechanical variations.
The parameters studied by Milankovitch included obliquity (axial tilt) & the precession index (which two factors control the seasonal cycle of insolation), plus eccentricity & longitude of perihelion.
vukcevic says:
May 13, 2014 at 2:10 pm
Good discussion on implications of Milankovitch cycles for possible fate of the Holocene:
http://wattsupwiththat.com/2012/03/16/the-end-holocene-or-how-to-make-out-like-a-madoff-climate-change-insurer/
No one can say if the Holocene will last half a precession cycle, a full one or more.
Or..
maybe it was the transition period to or entry into the S1 magnetic shell. Turbulence in the interstellar regions.
Figure 1 of,
“Time-variability in the Interstellar Boundary Conditions of the Heliosphere:
Effect of the Solar Journey on the Galactic Cosmic Ray Flux at Earth”
Priscilla C. Frisch · Hans-Reinhard Mueller
2011
http://arxiv.org/pdf/1010.4507.pdf
[/sarchasm That gaping whole between reality and the CAGW religion .. Mod]
Why would woo want wots of ws? You don’t know your arm from a hole in the gwowd.
@Sandi
“A bit annoying when reading a study raises more questions than it answers.”
Not at all! Without those questions, how would you apply for more grants?
@John Whitman 6:56 am:
“The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.” “
– – – – – – – – – –
Science in very blunt self-correction mode with that assessment of “conjured up “out of thin air” “.
Hardly, John. This small group of self-appointed guardians of the sacred trust (meaning their academic careers) has done NO work on this subjecct othre than to snipe at things that are mostly incosequential and trying to convince people through “Science by news release” that their opponents are wrong. But this group does NO original work, NO field sampling that isn’t done wrong, and rankly they got NUTTIN’.
The “conjured up out of thin air” is a snarc-y ad hoc attack on the pro-impact people. They have nothing else but snide comments. DO you see any professional respect in that? I don’t.
Snarc-y doesn’t make it self-correction.
Trust me: Meltzer is 100% invested in the Clovis Overkill hypothesis – the current mainstream consensus, which has holes in it big enough to drive a Mac truck through. If you think the CO2 CAGW hypothesis is weak, you should look into that one. But Meltzer If the impact hypothesis wins the day, Meltzer’s entire career is mammoth poop. Holliday does nothing but kibitz on the impact hypothesis. He is out of his league, but his career is caca, too if it flies. And the man hasn’t done ONE bit of science on this – just Op-Eds masked as science. It is all behind the desk pontificating.
The VAST bulk of the pro-impact scientists is forensics – samples, lab tests in about 12 different ways, quantified and collated. Holliday lets them do the work and then sits back and says, “But you forgot to put in that semi-colon! It’s bad science! And you are 10 years too early!” yep, like the C14 dating is that precise that anyone would know…
As Firestone says about their picayune points: ““Radiocarbon dating is a perilous process.”
@Bill Illis at 7:27 am:
“Speaking of 2 km high glaciers melting in a short few thousand years, can you imagine how big the floods were and how wide the rivers flowing south got in the summer melt season. The Mississippi would have been impossible to ford unless your species could build good boats.”
Bill – The 2km was not an average, nor was it 2km at the edges, as many people believe. The 2km was at the highest point,which was east of Hudson Bay – 600 km from the edge in Michigan. You can basically blame all the science writers who’ve ever written on this, for not clarifying it for the public. I had to go look high and low to find it out. At the southern edges the ice was “only” 1-3 hundred meters, though no one knows for sure. It might have actually been only a 20-30 feet high right at the edge in many places.
Remember, for the ice to retreat, it had to melt back at the edges. Glaciers today in Greenland are kms thick far from their bottom ends, but look at most of them at the leading edges and they are usually not 100 meters. The southern zone of the ice sheets was partially exposed to the warmth south of the edge, so it would have logically lost ice thickness the closer you got to the edge. As the ice sheets retreated, this thinning at the southern edge would have probably continued, until at one point all of the ice sheet was gone.
Your last sentence doesn’t really make sense. To ford a river is to WALK across it.