From UC-Davis:
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 droplets — 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 soil, 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 cosmic impact, 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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http://www.sciencedirect.com/science/article/pii/003358947790031X
I think the Gothenburg Magnetic Excursion in conjunction with very weak solar conditions could explain the Younger Dryas.
the Gothenburg Magnetic Excursion could also be evidence of an impact, affecting the relative rotation between the earth and the core, and thus the magnetic field.
Our grandchildren, if not ourselves, may very well get to document all the chaos a magnetic polar flip causes in detail. Perhaps things will be as drastic as they were at the beginning of the Younger Dryas. Already earth quakes and volcano eruptions seem to be on the increase, along with the acceleration of the movement of the poles.
There is veritable impact on science in this report.
This article is interesting and all, but, they total failed to replicate the original studies. The “scoriae” they investigate is not the same materials cited as evidence of an impact event by Firestone and crew. As I personally have reservations about an impact triggering the Y-D, I find the “critical” studies like this one very irritating. They fail to investigate the actual kinds of evidence that were cited by either the original “impact” paper or the follow ups. That is, the presence of nanodiamonds, the presence of carbon microspherules, iron droplets and other materials that would indicate an actual impact. Instead, they are looking at debris from cultural layers, where they know they will find soot and other by-products of household fires, and then report that they did not find evidence of an impact. Worse they look at material that they know spans several millennia where evidence of the “event” would be constrained physically to a very specific stratum. Bad science is not constrained to climate science.
Bad science is not constrained to climate science.
and neither are bad skeptical tactics.
Duster –
Amen.
It goes deeper than that. The supposed building fires at 13,000 years ago are a full 1,000 years before the beginning of agriculture and 14000 years before the first settlements (according to Nat Geo). So the authors did not even check to see if houses or buildings even EXISTED. (They did not.)
Good catch on the switcheroo of the materials. Surovell in 2009 pulled the same switcheroo by sampling very thick stratum and sampling in different spots on the site. Then he concluded that he, also, could find no evidence of spikes in the materials. He couldn’t follow sampling protocols, and he blamed the YD impact people for being wrong – when in fact he would have failed junior high chemistry for such failures to follow lab methodology.
We have no idea of what caused this or that epic climate event in the planet’s history.
“…I’ll never worry
Why should I?
Its all gonna fade…
Still
crazyclueless after all these years”(apologies to Paul Simon)
Although this article is of interest, it is only focussing on one small part of the planet. There are so many other indicators from other parts of the world of what was very likely a huge cosmic encounter. This signalled the beginning of the Younger Dryas approximately 13,000 BP. See also the book “Sudden Cold an Examination of the Younger Dryas Cold Reversal.
There are no valid indicators of a cosmic impact at that time.
You are welcome to your opinion.
Copernicus’ skeptics said there were no valid indicators that the Sun moved around the Earth.
Wegener’s skeptics said there were no valid indicators that continents move.
Until about 1810, scientists swore up and down that there were no valid indicators that rocks fall from the sky.
Harping back to my earlier post about the BBC’s Horizon science programme, they also did one around 15-20 years ago, (when it was a real science show) about cosmic impacts from asteroids & the like. The show suggested that there are 100s of potential collision bodies around the Earth. Once scientists had detected the remnants of an old crater, they seemed to have discovered many impact craters all around the Earth, & those were just the land based ones!
The count of potential collision bodies is up to over 1400. And their scan of the skies is only about 10% done.
The guys over at The Cosmic Tusk will not be amused.
Oh, dude, I was so amused I didn’t know where to start ripping this apart. See below…
But first, see Duster’s comment above at January 7, 2015 at 11:12 am. He is not a CosmicTusk guy. And he has reservations, as he says, about such an impact. But he nails this paper to the wall.
Samplinging the wrong materials from the wrong microlocations means that all further discussion about those materials is a moot point. The YDIH skeptics have pulled this one before.
As Steve McIntyre often says, “You have to keep your eye on the pea.”
MY main thing is that I know how old agriculture and civilization are. They are not as old as 12,800 years ago. So discussions of “building earth” are absolutely ludicrous and ill-informed. Buildings didn’t exist 12,800 years ago, so building fires could not have occurred. You can’t burn what doesn’t exist yet.
The oldest buildings on Earth are at Gobekli Tepe, which is 12,000 years old. And what was Gobekli Tepe’s temple built of? Stone. BIG 1-piece stone columns (not totally unlike at Stonehenge) and stone in-filled walls.
Try burning a stone building sometime. It is KIND OF hard to get the fire going.
Try burning down Stonehenge.
A possible mechanism for rapid warming out of the last ice-age then small rebound to cooler temperatures goes as follows. Arctic and Antarctic glaciers slowly grow out over open ocean. This crimps annual sea-ice build inhibiting deep water upwelling closer to the equator leading to less low cloud formation resulting in quite rapid warming. Eventually one or more major overhanging glaciers suffers catastrophic fracture opening a much greater area for annual ice build leading to a small period of cooling. What drives the initial warming is likely orbital parameters plus the fact that the earths received solar wind increases as the earths orbital inclination increases
Just wondering… If there was a major comet/asteroid impact that hit a glacial ice mass a mile or two thick how deep into the underlying earth might the penetration be and how much evidence as mentioned in the article would there actually be? Also, it seems like the heat energy from such an event would release a tremendous amount of moisture likely supersaturating the atmosphere of the whole planet. After this it rains, a LOT. Flood legends, 40 days and 40 nights of rain, quick frozen mammoth carcasses with green grass in their digestive tracts (far north snow instead of rain, LOTS of snow) all indicate something very big and unusual happened. Ancient myths and legends likely have some (if not a lot) of basis in actual events that have been distorted but not totally lost as the generations passed. Humans from 15,000 +/- years ago were just as capable as humans born today.
hi Milodonharlani: With due respect, there are many indicators of what many believe was a cosmic encounter with a comet (pieces of) 13,000 BP. They include carbon 14, beryllium 10, nitrates, ammonium, and the much touted nanodiamonds; still from a number of locations around the world. And many intriguing other features such as: extremely rapid onset of severe (almost glacial cold) in most of the world, (perhaps aside from Antarctica). And all of this fits well with what a number of astronomers including: Dr. William Napier, Dr. Victor Clube and Dr. Duncan Steel have postulated for years. Rod Chilton.
None of those alleged indicators is valid. The long awaited nanodiamond isotopic analysis late last year showed no difference, although work continues. Also last year it was discovered that ET lonsdaleite is just a disordered form of ordinary diamond. At every turn the skeptics have been shown correct. But it seems that nothing stops the true believers & careerists, who just reformulate their hypothesis anew or attack the bearers of bad scientific news.
Both studies may be found here, although you,ll need to search for them:
http://cosmic.lifeform.org/
Extraterrestrial Lonsdaleite is Structurally Defective Diamond
Atom-Probe Tomography and Nanodiamond Isotope Analysis
The nanodiamonds were not formed from ET material but from terrestrial material subjected to very high temperature and pressure induced by the impact, so the isotopic analysis is aimed at a strawman.
“None of those alleged indicators is valid.”
And yours is the only opinion that counts. You must have 97% consensus on that, I assume.
Thanks for informing us.
So what finished off the mammoths, then? Or are they still around somewhere?
RoHa:
The mammoths weren´t killed off by the YD. They survived until 3600 years ago. What wiped out the last isolated survivors is subject to debate.
Mysteryseeker:
There are no valid indicators. All have been thoroughly debunked in detail, but the YDIH adherents just keep moving the goalposts.
Last year two more nails in the coffin were added, but the zombie hypothesis still staggers on. Lonsdaleite was found to be a disordered form of ordinary diamond. The eagerly awaited nanodiamond isotopic analysis preliminarily showed no difference in terrestrial & ET ratios, although work continues.
There is no reason to suppose that an impact caused the YD. It´s no different from other such climatic swings & the extinctions supposedly owing to it weren´t.
“the zombie hypothesis still staggers on.”
Zombie mammoths? We’re doomed!
Holy crap, all I want to do is de-fund the windmills.
Now you try to bury me in muck, mire and science.
It almost seems like you think our elected officials will listen 🙂
“Dense concentrations of mammoth bones, tusks, and teeth are also
found on remote Arctic islands. Obviously, today’s water barriers
were not always there.”
Or mammoths were excellent swimmers.
Mods – the length limit of posts needs to be much shorter. We’re drowning in mammoth crap.
Folks reading with mobile phones especially iPhones could start sue-ing WordPress for RSI of the thumb.
Should that be Alan Dershowitz or Paul Cassell?
Or maybe Amanda’s implant?!
The thing that is being over looked is is the Younger Dryas is not a one time event. There were many abrupt dramatic swings 20000 to 10000 years ago probably due to the fact that the initial state of the climate was very close to glacial versus inter- glacial thresholds during that time .
The Oldest and Older Dryas were also periods of rapid climate change and there is no way all these climate changes were cosmic in origin.
A valid argument. One that is often given. The big swings actually goes back to nearly 50,000 years ago. So the YD advocates must explain those, also, in order for their lab results to be valid, right? With the silly skeptics papers like this one out there, no progress will be made toward looking past the forensics until those forensics are widely accepted. No work at all can be done yet to rectify the seeming discrepancy you point out. They can only jump one hurdle at a time. To address that one is to put the cart before the horse.
I myself can see ways around it. Are my ways valid? No, but they are reasonable/plausible, if even only to me right now.
Seriously, be aware of this:
If the YDIH is ever accepted widely – making a new paradigm in essence – many things will have to be re-interpreted – data, papers, evidence, ice cores, Bond events, Dansgaard-Oeschger events, climate change, extinctions of animals, and even uniformitarianism itself may be modified. That is not a full list.
As to those very rapid climate changes, let’s throw this at you:
[Wiki – Dansgaard-Oeschger events] “The processes behind the timing and amplitude of these events (as recorded in ice cores) are still unclear. The pattern in the Southern Hemisphere is different, with slow warming and much smaller temperature fluctuations. Indeed, the Vostok ice core was drilled before the Greenland cores, and the existence of Dansgaard–Oeschger events was not widely recognised until the Greenland (GRIP/GISP2) cores were done; after which there was some reexamination of the Vostok core to see if these events had somehow been “missed”.[verification needed]
A closeup near 40 kyr BP, showing reproducibility between cores.
The events appear to reflect changes in the North Atlantic ocean circulation, perhaps triggered by an influx of fresh water.”…
…”The ice core’s signals now recognised as Dansgaard–Oeschger events are, in retrospect, visible in the original GISP core, as well as the Camp Century Greenland core.[15] But at the time the ice cores were made, their significance was noted but not widely appreciated. Dansgaard et al. (AGU geophysical monograph 33, 1985) note their existence in the GRIP core as “violent oscillations” in the δ18O signal, and that they appear to correlate to events in the previous Camp Century core 1 400 km away, thus providing evidence for their corresponding to widespread climatic anomalies (with only the Camp Century core, they could have been local fluctuations). Dansgaard et al. speculate that these may be related to quasi-stationary modes of the atmosphere-ocean system.”
The YD is the only one of those “violent oscillations” that has been seen to actually make consequential changes to the climate. The “Dryas” part applies to the change in climate in Sweden that was illustrated by the dryas plant, a tundra plant. It wasn’t there and then it was. Twice – in the older Drays and then again in the Younger Dras.
Our evidence IS mostly the ice cores, for the violent nature of the swings – but how big were they, really? All of them?
And are multiple meteor strikes within that 50,000 years out of the question? Not according to some astronomers. Ever heard of the 8.2Kya event? It’s in Wiki. Was it an impact of a lesser nature? How about the 536 AD event? Were there more? Ever heard of the Taurids? (Tungska seesm to perhaps have been one.) Encke’s comet?
Why are Bond events so regular? As were D-O events? And the same length of spacing – one in the Pleistocene and one in the Holocene. Nothing on Earth has been identified as having a 1470-year cycle. Could it be meteors?
Whatever your answer, are you SURE?
I am not. I don’t know the answers. But at least I am looking and encouraging others to look.
Nice picture though!
http://wattsupwiththat.com/2013/06/02/multiple-intense-abrupt-late-pleisitocene-warming-and-cooling-implications-for-understanding-the-cause-of-global-climate-change/
As one can see the Younger Dryas event was not an isolated climatic event.
There’s only one theory that I know of that explains the mammoth findings — the one put forward by Immanuel Velikovsky. Remember, there have been findings of mammoth with “fresh” meat, and individuals preserved well enough to determine that they fed on tropical flowers.
For this to happen, the climate needs to change from being temperate to being frozen quickly enough that the stomach contents of these large animals do not complete their digestion. And then they need to remain frozen into the present day.
I wish to stress that the onset of the Younger Dryas was likely as rapid as one year or two (there are references ) and the severity of the Younger Dryas though interrupted at times throughout the 1300 year long interval, was extremely cold, up to 15 degrees Celsius in Greenland and almost as much in Western Europe. This was much more extreme than either the Older or Oldest Dryas. I am not certain that Dr. Richard Firestone would be a quick to give up the nanodiamond proxy.
That would require him to give up on a long career or crusade.
The YD was also more pronounced than the following 8.2K event but not than many of the similar cold snaps in the previous geologic record. There is no need for special pleading in its case. To the extent that it was more pronounced, ice melt conditions adequately explain its observed character.
“That would require him to give up on a long career or crusade.”
You are amazingly ill-informed. Firestone has almost completely dropped off them map on the YDIH. There is no indication that he has done a paper on it since about 2009.
Not much of a crusade – 2 papers and a book…
There were events greater then the Younger Dryas according to the data I just sent.
Actually, dude, if you are talking about that WUWT post link, if you look at the GISP temperature graph (Figure 2), you are mistaken.
The start of the YD shows a 9°C drop in temps – the largest drop on the graph, as well as the most sudden. If you are talking about the entire YD stadial, that is not what the YD impact Hypothesis is addressing. It only addresses the onset. The end of the Younger Dryas or the end of the Older Dryas are other issues altogether.
Confusing the two as one issue is like confusing a gas pedal and a brake, and arguing that what one does is tied to the other, and that the explanation of one is necessarily tied to the explanation of the other.
Hi again Mildonharlani and also Salvatore Del Parte: It just so happens that the 8,200 BP interval though mostly less severe than the YD, did have an even more severe drought in Africa for instance. Also, I would ask of Salvatore, what other intervals had more a more severe climate in the last 15,000 years or so? I do not believe there were any.. Finally, what would you both suggest was the cause of the Younger Dryas and the 8200 BP intervals? Surely not the outmoded slowing of the North Atlantic Ocean Circulation. Rod Chilton.
Rod,
The entire, thousands of years long Last Glacial Maximum was colder than the YD, as were Heinrich Events, which have similar traits & probably causes to the rapid cooling events during transitions from glacial to interglacial phases.
I don´t know what you suppose is outdated about the well supported explanation for the YD & similar events, but the effect of fresh meltwater on thermohaline circulation is still the leading hypothesis, with abundant good reason:
http://www.ncdc.noaa.gov/paleo/abrupt/data4.html
So what if there were warmere or colder periods than the YD stadial? The issue isn’t max or min. The issue is the suddenness and the degree of drop – and what possibly could have caused such a sudden and severe change.
Look, dude, Firestone didn’t invent the Younger Dryas. The biologists did. And he wasn’t looking to solve it. He is an isotopes guy at Lawrence Berkeley. Lots of other people got involved, and now Firestone is hardly a blip on the map anymore.
If you think the climate was the cause, why do you think there are other people out there suggesting other solutions? Because the climate thing by itself doesn’t do it. They are all smart dudes, the climate guys and the impact guys. But none of them has won the day yet. So it is still an open question.
Why does only the impact idea get slammed in the popular science press? Ask that one some time.
Exactly, on the 8.2 kya event. Good get.
Hi Milodonharlani: I agree that the LGM was colder as were similar Glacial periods prior to the last one, and yes there were considerably longer as well. However, the Heinrich event were not as cold nor as widespread as the YD. Oh and I think the subject of the North Atlantic should be well and truly dead. If you wish to see what an expert, oceanographer, Dr. Carl Wunsch states about this check his website out. Rod Chilton..
Heinrich events were colder. as they occurred during the glacial phase, including at both ends of the LGM. Most of the roughly 100K years of the last glaciation were colder than the YD, as of course too were prior glaciations. The YD was nothing special at all & needs no special explanation. It´s just another ordinary fluctuation in climatic cycles.
http://en.wikipedia.org/wiki/Heinrich_event#mediaviewer/File:Heinrich-events.png
Dunno what part of Wunsch{s work you have in mind. Maybe his thoughts on D-O cycles or his modeling of deep ocean circulation? Both predate my NOAA link. Please be more specific. Thanks.
“The YD was nothing special at all & needs no special explanation.”
Once again, it wasn’t any impact people who started the buzz about the Younger Dryas. It was the biologists. Then the climatologists. THOSE are the people who say this statement is wrong. They know something weird and big and unexplained happened.
“It´s just another ordinary fluctuation in climatic cycles.”
If you base that on solely the Greenland ice cores, don’t. The southern record shows much smaller ups and down. What was the overall Younger Dryas effect? We can’t go by 3 ice roes in Greenland and extrapolate the whole globe off them, not without some other sources that agree on both the timing and the magnitude. And those don’t exist at present, so you can’t say what you said and expect it to be true.
One issue which is not discussed that much is that, when the glaciers started melting, the water outflow expanded lakes by 100s of kms and made every major river flowing south/west/east to the sea, about 100 times bigger.
Any species that did not have a boat (all of them that is except us and maybe the polar bears) could NOT (and NOT is 100% true in this case) ford the Mississippi River started about 13,000 years ago and ending about 7,000 years ago. If a Mammoth herd decided to try to cross the Mississippi at 11,900 years ago, they were all doomed.
All the large animals that migrated to some extent, faced this dillemma from 13,000 years ago to 7,000 years ago. Do we go back or do we attempt to swim for it. The Lake is still rising and we are stuck on this island. Do we make a swim for it. Our herd has always crossed this river in June but now it looks twice as fast. Do we swim for it. These decisions were faced at least every week. Entire herds of every large migrating animal were wiped out on a regular basis by just trying to swim for it.
The reproductive capacity of large animals is not high enough to compensate for these “doomed swim for it” deaths.
In addition, most of the large animals were, in fact, large herbivores living on grass. As the ice ages ended, the extent of grassland reduced by something like 2000%. The large animals needed to migrate more to find what they were looking for. Some of them, like the Mastodon, were small brush leaf eaters but they needed an extensive expanse of small bushy plants to sustain themselves and as larger trees recovered during the ice age melting, they disappeared.
Now throw in human hunters with atlatls and cliff jumps, whereby whole herds could be killed off so that hunter gatherers could obtain 1/10th of the herd’s meat to keep them well-stocked for a few months (note that a hunter-gatherer society is consistently experiencing periods when they are going to sleep without eating ANYTHING in the day and they would not really care if they killed off 10 times more animals than they needed to in order to eliminate that night-time hunger for a few weeks – I dare you to not eat anything tomorrow), well, that helped lead to extinction of all the large animals.
Glaciers melting, water everywhere, human cliff jumps, hunter-gatherers deciding that over-kill is better than hungry nights, that is all that is needed to wipe out several dozen species of large animals.
The human hunters are what made the Holocene different from prior interglacial transitions.
Early Holocene humans were spread very thin across the North American landscape. The picture of their somehow prodigious food-consumption driving an extinction crisis is hard to bring into focus.
Mammoth and mastodon hunt-remains are disproportionally in bogs, which are a great danger for very large beasts. Local humans ‘improved’ their local wetlands, and ‘managed’ trails around them. When a beast was found in their area, they would drive it along ‘fenced’ trails, and onto the soft ground that was camouflaged. Their weight then doomed them; just wait a few days.
To ‘track down’, chase & spear or shoot an elephant with arrows is a very dicey proposition … and I propose that it was uncommon and abnormal, until eg after domestication of the horse. Dogs are not effective against elephants. Sharp sticks are too puny … elephants are quite fast, and display awe-inspiring fury. They’ll kill human tormentors very dead, out on open ground.
How come elephants are not extinct in Africa or Asian?
What could one do with an elephant-carcass, a long ways from their living site? Very, very little. Even a modern deer-hunter knows to resist that good-looking buck … way down the hill in a deep draw, or at the end of long, brushy hike from her vehicle.
No … mammoths and other large, mobile beasts are unlikely to have been unduly pressured by early Holocene humans. Something else undercut them.
Paleo-Americans didn´t use arrows but atlatl darts tipped with Clovis points.
Human predation was sufficient to wipe out large species over time when they were already subject to the sorts of pressuress described so well by Bill. It doesn´t take much, as witnessed by extinctions elsewhere when humans invade continents or islands with naive prey populations.
Humans and elephants evolved together in Africa. Mammoths (and mastodons, which aren´t technically elephants) in North America were not used to human predation so fell as easy prey.
Species subject to predation do not have to evolve with particular predator-species to recognize predation-behavior by them, and exhibit the typical stimulus-response (prey avoids, flees from anything that acts predatory).
North American game-species did not recognize humans as predators when they first showed up, but they recognized predation-behavior by them, instantly, and adjusted their perceptions of humans, promptly.
North American deer did not evolve with firearms, but today they recognize ‘hunting season’ with the first fall rifle-shots in the woods. They then become very much more difficult to locate. Many game-populations are ‘introduced’ to firearms, unawares & naive … but every populations of every species ‘figures out’ what guns mean and how to respond to them, promptly.
No, the first Americans got exactly one free shot at the naive big-game, and then they wised up in a hurry. ALL of these animals were heavily predated, continuously, and they all reacted to the behavior, not the species.
Adult mammoths were not subject to predation. Saber tooth cats &npossibly lions & short faced bears may have preyed upon babies, but only at great risk.
Mammoths were not used to the hunting practices of people, such as stampeding them into bogs or off cliffs. Humans killed off the cows & calves, then moved on to new areas with still naive populations.
Deer, elk & even pheasants, whose lives are short, soon learn to gang up & find relative safety from hunters with fire arms, but deer were not wiped out by the Clovis people- Less adaptable bigger game with longer gestation periods. for whom hiding cover is harder or impossible to find´& more specific feeding needs however were.
The evidence of oceanic islands, Australia & New Zealand show what human predation can do, ie cause extinction of large prey species.
Adult mammoths were not subject to predation. Saber tooth cats &npossibly lions & short faced bears may have preyed upon babies, but only at great risk. [emph. added]
It would be no less risky for humans to mess with mammoths, than it was for carnivores. They will wheel & turn on a threat, from any species. “Panic & run into the bog, my hind foot! I’ll trample you to a grease-spot, instead!” Paraphrasing.
Predators as a rule do try to pick on the young, weak and old. That this would also be the case with mammoths, wouldn’t materially qualify their status as prey.
‘Traditionally’, saber-tooths were presumed to live high on the megafaunal hog, including (if not ‘especially’) mammoths. Lately, another interpretation aims to make the case that hyper-canines are (perhaps counter-intuitively) not about hyper-big prey. Instead, this adaptation expresses & supports a fundamentally divergent hunting-technique (kill-method), which was applied to normal-sized prey. This newer take on the saber-functionality would (if true) free megafauna from a ‘dedicated’ predator (and promote the ‘not subject to predation‘ position).
Exaggerated canines have been repeatedly revisited, across evolution. Eocene-Pleistocene sabers are sported by a large variety of animals, presumably occupying a comparable variety of niches.
However, if saber-tooths were able to get along fine on common prey, their own subsequent extinction then becomes harder to explain. Average-size prey-species are the ones that made it through the extinction-event. Normally, saber tooth tigers are said to have died out, because the megafauna they were specialized for & dependent upon, die out.
Ultimately, extinction, like climate change, is a pervasive fact of Nature … and nailing down either general or specific causes looks like a work in progress.
Damn, Ted, I can’t believe it, but for once I agree with you. Those have been my arguments since the first time I heard the Overkill theory. How DUMB s it to kill an elephant or mammoth when you can’t eat it all nor take it all back with you. Better to hunt stuff you CAN take back.
Also, if you look at the distribution of Clovis sites around N AMerica, you quickly see what they don’t tell you with the Beringia idea, (whether right or wrong about that). What do you see? The vast majority of Clovis sites are in the US Southeast, south of the Ohio River and east of the Mississippi.
There are also only 11 Clovis sites that are also demonstrated mammoth or mastodon kill sites. NONE of those are in the US Southeast.
What does it mean? Nothing conclusive, except that the Overkill Theory may need some considerable reworking.
Yeah, though the original concept had that piquancy and free-thinking irreverence we like so well (wut? Indians not eco-geniuses? oh no!), once it gets suited-up and enters the octagon of real hypothesis-competition, it comes up a rookie.
It’s an eye-roller, every time someone trots out the ‘buffalo jump’ as instrumental in continent-wide extinctions. Such jumps are notable & memorable, owing in large part to their scarcity. And what will an isolated 11-person hunter-gatherer group do with 100 tons of rotting buffalo? How does such a spectacle increase their fitness?
Bogs; same kinds of limitations-issues, particularly in the temperate zone. Many parts of the country lacked bogs. In some big regions that had them, the terrain & vegetation-cover worked against using the soft ground as a trap. Bog-traps need favorable & cooperative surroundings; by no means will just any ol’ muck-hole do.
Getting a decently-situated bog to actually work, virtually always takes a lot of work, improvements. There is recurring, twice-a-year upkeep, and there is material preparation to be done. Fire (smoke) would be the most efficient & effective driver, and this requires cached fuel, known & prepared fire-sets, and intimate knowledge of the routes between all the action-points & support-resources.
Yes … in fact it does not take much of a pit-fall to gravely injure an elephant. Just a couple yards tumble, and we’re talking a megafauna critter in big trouble. The ‘pit’ does not have to ‘contain’ the (mega-)animal – ‘the damage is done’, just by the fall. Even an unexpected drop of only 2 or 3 feet can easily mean a lame or crippled beast. Horse riders live in fear of mere gopher-holes.
And local bogs, once ‘tuned up’, give evidence of having been recurring game-getters.
===
Whenever & wherever there is a persistent “mystery”, there is the chronic temptation to step into the vacuum and offer a resolution … and (er, because) there is always an audience for such efforts. Extinction is a huge mystery … and a huge fact of Life.
There is an archaeological trend, toward greater status for, more widespread use of, and earlier occurrence of the ‘landscape game-fence’. Usually, these are not impervious barriers, but are erected as ‘suggestions’ to ‘prompt’ path-selection by (usually) migratory animals. Such fences sometimes ran for impressive distances, and incorporated very clever landscape-integration devices. While these fences would reduce the outlay involved in harvesting animals, they also plainly point to major investment & commitment which then tied groups & cultures to their particular locale.
In order to have exterminated many species of megafauna, aboriginals would have had to journey deep into the refugia of such types of wildlife, making it their priority to seek scarce sorts of game, even while ignoring easier solutions to their grocery-needs. Growing signs of increasingly important fences, at earlier dates, suggests that the Paleoindians of America settled more quickly & comfortably into homebody-mode than formerly assumed, and were thus not the type to press deep into unfamiliar habitat, ‘on some wild-elephant-chase’.
(Reposted from an earlier nano diamond thread):
phlogiston on August 30, 2014 at 5:32 am
The Bolling-Allerod (Northern hemisphere warming at 14,600 yrs ago) and Younger Dryas (subsequent 1000 yr cold interval) were parts of the last deglaciation which were driven by oceanographic processes. There is no need for an atmospheric deus ex machina. Over the deglaciation starting as early as 22yrs ago the general picture is steady changes in Antarctica contrasting with unstable fluctuations in the NH driven by the Atlantic Meridional Overturning Circulation (AMOC). The root cause of this is an instability in the AMOC arising from a positive feedback which it possesses.
Cold water formation and downwelling in the Norwegian sea drives the gulf stream – reactive flow of Carribean warm and – critically – saline water across the Atlantic to north west Europe. This gulf stream water has high salinity, and this makes the cold water formed in the Norwegian sea even more dense than would result from its temperature alone. So this cold and saline water sinks all the way to the Atlantic floor and is one of the principal drivers of the global thermo haline circulation (THC). Now more of this “deep water formation” at the Norwegian sea actually speeds up the gulf stream – something has to replace all that sinking cold super-salty water so this is supplied by the gulf stream. Thus the positive feedback – more gulf stream leads to more cold supersaline Norwegian sea downwelling leading to more gulf stream etc.. Where you have a positive feedback in the system you have the conditions for nonlinear oscillation. This is directly analogous to the ENSO in the Pacific, the positive feedback of the Bjerknes mechanism (cold upwelling strengthens trade winds strengthening cole upwelling etc.) giving rise to the ENSO nonlinear oscillator, although the AMOC operates over much longer – century and millenial – timescales than ENSO (decadal).
So a basic oceanographic feature comparing the NH with the SH in the palaeo record is more fluctuation and instability in the NH and more stable, gradual changes in the SH. The nonlinear instability of the AMOC is the root of this. Also, there is a clear signature of interhemispheric bipolar seesawing, whereby when the NH moves in one direction, the SH moves in another. This is not universal however – sometimes at the moments of biggest transition, NH and SH move together.
About 22 kYa (thousand years ago) Antarctica started warming. The NH at the same time slightly cooled. However at about 14 kYa the “Bolling-Allerod” (BA) happened, i.e. the NH abruptly warmed, as evidenced by Greenland cores. This caused a reciprocal pause and slight reversal in the (already long established) gradual Antarctic warming – the bipolar seesaw again. At the time of the BA there was a sharp rise in global sea level – 20 meters in 500 years. Weaver et al 2003 (link below) show that this was caused by a collapse of the gradually warming Antarctic ice sheet. The pulse of fresh meltwater from Antarctica had the effect of speeding up the AMOC and the gulf stream in the NH, bringing rapid warming to the NH and the BA.
The bipolar seesaw continued – as the NH became sharply warmer, there followed in the SH the “Antrctic reversal” where temperatures went slightly into decline. However down in the deep ocean, interactions between cold bottom water formed in the Antarctic and Arctic caused – about a thousand years later – an abrupt stoppage of the AMOC and the gulf stream. In fact the cuplrit was Antarctic Intermediate water (AAIW) – see again Weaver et al. With the interruption of the gulf stream the NH went cold again – the Younger Dryas. In response – by now you get the picture – the Antarctic turned to gradual warming. After about 1000 years of NH cold with no gulf stream, the effect of the Antarctic collapse subsided allowing the AMOC and the gulf stream to resume. Now followed an exception to the bipolar seesaw – both NH and SH warmed together, around 12 kYa. This marked the final end of the last glacial and the Beginning of the Holocene.
http://rockbox.rutgers.edu/~jdwright/GlobalChange/Weaveretal_Science_2007.pdf
http://epic.awi.de/15280/1/Lam2004a.pdf
I have been wondering for awhile what the affects of the changing sea level had on the thermal haline?
Not surprising
Like Global Warming, the Asteroid Dino hypothesis gained popularity not through evidence (there’s very little) but due to politics. Basically it’s message was “Nuclear Winter Killed the Dinos so Just Think What Will Happen to Your Children So We Must Stop Reagan!!”
After the cold war ended it stayed around because of it’s Hollywood coolness factor, the Dinos are near & dear to our hearts and going out in a bang seems like a fitting end.
Now they go for comets wiping out the Ice age mammals because it fits with the Liberal Noble Savage Myth. It hurts the Liberals sensibilities that “Noble and pure” ancient man drove all those animals extinct. So they invented Comets & Asteroids to do the trick instead.
Some Hypothesizes have 5 or 6 different comets hitting to explain all the extinctions, which is just the same as more & more epicycles
An Asteroid killed the Dinosaurs and later one killed the Mammoth Scientists are almost as bad as the alarmist.
Here’s as extreme example
This study found that Iridium is missing from the Chicxulub crater itself!!!!!
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1811.pdf
So the question is how can an Asteroid or whatever that caused the Chicxulub crater produce a iridium spike around the world when it didn’t contain iridium?
The findings in that report clearly show that whatever happened at Chicxulub has nothing to do with the K-T yet the scientist(s) refuses to even consider the possibility, They even say so in the paper, Quote from the conclusion “If we exclude the extremely implausible assumption that the K/T boundary is not related to the Chicxulub impact event”. That is just poor science and sounds like the alarmist, You can’t just exclude evidence you don’t like.
The nuclear winter scientivist scam came after the K-T impact hypothesis, not before it.
The authors of the study you cite plainly do not agree with your conclusion. Evidence in favor of the impact hypothesis for that mass extinction event is overwhelming. OTOH, there is no valid evidence in support of a YD impact, not even a crater.
Nanodiamonds and the Younger Dryas extinction, Aug. 28,2014:
http://www.news.ucsb.edu/2014/014368/nanodiamonds-are-forever
It’s worth reading some of the russian discoveries of mamoths. Some have been found with food still in their stomachs and more recently, recoverable blood.
Then think how cold it would have to be to stop internal decomposition almost instantly.
It doesn’t have to happen instantly. Normal subarctic cold will do the trick fine.
The wetlands and boglands and swamplands of the high north are vast, and they are also by far the richest grazing and browsing habitat. But mammoths cannot venture onto such soft & ‘bottomless’ conditions, until winter has frozen them rather deep.
There was always pressure to return to the winter feeding-grounds, as early as possible, and this itself claimed many, many hairy elephants. Some bogs & pools are warmed by decomposition, and will be froze-over only thinly, compared to surrounding sites. Deeper snowfalls, which are not the norm in these arid regions, would make it very treacherous for the big animals, being then unable to properly assess ground-conditions by sight, before stepping on it.
Even moose, caribou, buffalo and elk have these problems. In the USA, we’ve had a herd of 21 elk drown after breaking through the ice, in Colorado, just in the last couple weeks.
That’s how mammoths are ‘frozen in their tracks’, with undigested food in them.
Thank you. That is the best explanation for the frozen-food-in-stomach aspect of the Mammoths that I’ve heard.
Thanks for the nice words! Yeah, there’s a bunch of oddities grown up around ‘instantly-frozen’ mammoths. They are found standing, even running, ‘frozen in place’, because they were trapped, struggling in ‘quicksand’. Even a small mammal, even dipped in liquid air, would collapse and thrash some, before it froze completely stiff … won’t appear ‘life-like’, but will ‘look dead’.
Air itself will rain & snow out before it can get cold enough do what they showed in Day After Tomorrow (people frozen rigid in mid-movement) … and still couldn’t do it that fast.
Cold doesn’t ‘go in’, heat has to ‘come out’; move, flow. Fourier made his mark with The Analytic Theory of Heat neigh 200 years ago, and we name the Fourier Series and Fourier Transform in recognition of his breakthroughs on the movement of heat.
Salad will last quite a few days in an ordinary fridge, still presentable. There’s no problem with food in a mammoth’s mouth or stomach not rotting away in the subarctic chill. We can even accurately identify Ice Man’s last meal, in the Temperate Alps.
Yer local home-construction contractor (who has to meet insulation standards & regs) has more heat-transfer acumen under her little fingernail, than these guys using mammoth ice-statues to argue eg for preternatural pole-flipping effects, etc. 😉
The problem facing climate science is ,
Climate sensitivity to various forcings is exponentially dependent on the mean state of the climate and earth dynamics (state of the earth ) which results in so many climatic outcomes and correlations breaking down over periods of time.
Phlogiston point 4 does not support your theory which you presented above.
What can we learn from all of this?
(1) The ice core isotope data were hugely significant because they showed that the Younger Dryas, as well as the other late Pleistocene warming and cooling events, could not possibly be caused by human emissions of CO2 because they occurred thousands of years before such emissions had any effect on atmospheric CO2.
(2) The magnitude and intensity of multiple climatic fluctuations has been up to 20 times larger than warming during the past century.
(3) Single events, i.e., volcanic activity or cosmic impacts, cannot have caused the abrupt Dansgaard/Oerscher warming and cooling events because of the multiplicity of warm/cold events over periods of thousands of years.
(4) The absence of a time lag between the N and S Hemisphere glacial fluctuations precludes an oceanic cause and is not consistent with the North Atlantic Deep Ocean Water hypothesis for the cause of the Younger Dryas.
(5) The abruptness of the climate changes and their multiplicity could not have been caused by slow, Croll-Milankovitch orbital forcing