January 02, 2009
More Evidence For Asteroid Clovis Extinction
A mere 12,900 years ago Clovis civilization in North America got brought down by an asteroid.
Abundant tiny particles of diamond dust exist in sediments dating to 12,900 years ago at six North American sites, adding strong evidence for Earth's impact with a rare swarm of carbon-and-water-rich comets or carbonaceous chondrites, reports a nine-member scientific team.
These nanodiamonds, which are produced under high-temperature, high-pressure conditions created by cosmic impacts and have been found in meteorites, are concentrated in similarly aged sediments at Murray Springs, Ariz., Bull Creek, Okla., Gainey, Mich., and Topper, S.C., as well as Lake Hind, Manitoba, and Chobot, Alberta, in Canada. Nanodiamonds can be produced on Earth, but only through high-explosive detonations or chemical vaporization.
Last year a 26-member team from 16 institutions proposed that a cosmic impact event, possibly by multiple airbursts of comets, set off a 1,300-year-long cold spell known as the Younger Dryas, fragmented the prehistoric Clovis culture and led to the extinction of a large range of animals, including mammoths, across North America. The team's paper was published in the Oct. 9, 2007, issue of the Proceedings of the National Academy of Sciences. (News release on the 2007 paper is available at: http://tinyurl.com/82988t, with link to a copy of that paper.)
We really should develop a much bigger asteroid detection and tracking system and an asteroid defense system. Really, I'm serious. This is more important than the manned space program and more important than probes that go to other planets. Heck, there's even a scientific angle because knowing a lot more about asteroids will provide insights into the solar system's development and even identify asteroids useful for terraforming Mars.
They're wrong, obviously so. The megafauna disappeared in South America at the same time. There is no way that a meteorite or meteror shower could blast two continents at once. There may well have been a meteorite, but it didn't cause the extinctions: paleoIndians did. The megafauna did _not_ disappear until much later in the Caribbean islands, Wrangel, and the Pribilofs - not until people showed up.
Look, megafauna disappeared when human showed up in Australia, the Americas, Madagascar, New Zealand, and miscellaneous islands. Different times, different climates - the shared factor is arrival of modern humans.
It's a hell of a lot more important than spending tens of trillions just in case global warming might be a serious problem.
knowing a lot more about asteroids will provide insights into the solar system's development and even identify asteroids useful for terraforming Mars.
Hey, if humoring Zubrin about terraforming will get us an assay of the nonterrestrial resource base, I'll even consider dissing O'Neill!
One project I like to improve asteroid detection is Orbit@home
It's still in beta, but work units have been sent out and it got some NASA funding. Worth bookmarking:
Did an asteroid cause the actual Clovis civilization collapse?
Has hunting of a food animal ever resulted in its extinction by an ancient people? Destruction of its habitant, sure but the complete annilation of a species, much less multiple species by hunting alone? Also wouldn't these large animals be rather difficult to kill. Yes, there is evidence that some animals were driven over cliffs but how often could this occur? The theory that anicent humans wiped out species seems to have a great deal of acceptance among folks who have never hunted.
The simultaneous loss of large animals in South America could be at least partially explained by the resulting drop in temperatures.
A collision with an extraterrestrial body seems to neatly explain the demise of the megafauna and the Clovis civilization. The collision would have reset the development of civilization in the Americas. Perhaps in an alternate Universe Columbus came from the west rather than the east.
We ought to have more robust asteroid monitoring and exploration program. But the money will go into Social Security and Medicare. Our granschildren if we have any will laugh at us.
The only reason needed for the collapse of a culture hunting big game is the disappearance of the big game.
"Has hunting of a food animal ever resulted in its extinction by an ancient people? " Yes: often. Look, we know that climatic changes are not the driver, because there have been other interglacial periods very similar to the one we're how that did not knock out many big animals. For example, the Eemian, about 125,000 years ago. Examples of such wipe outs: all the big animals in Australia, about 40,000 years ago. Which meant giant kangaroos, big flightless birds, 7-meters relatives of the Komodo dragons, a tortoise that weighted as much as Volkswagen Bug, a giant wombat (Diprotodon) the size of a hippo. etc. It happended in Madagascar starting about 2000 years ago, it happend in New Zealand about 800 years ago (no more moas).
Hunter-gatherers hunt for a living, not for fun. With brains and tools, they're better at it than any non-human predator has ever been. They went after big game because it paid off: per pound, catching and killing a giant sloth is a lot more profitable than chasing jackrabbits. Unfortunately, since those big animals have low rates of reproduction, it's also a lot more likely to wipe out the species.
Humans are far more likely to wipe out a prey species than other predators because they have a wider range of prey species and because they are omnivorous. A specialized predator will never wipe out its prey species: if the prey becomes rare, so must the predator. But when giant turtles or ground sloths became rare, Paleodindians switched to mammoths. Even when _all_ megafauna became rare, humans switched to plant foods and small game, but they were still around, still numerous (even if not quite as numerous as they had been when the megafauna was still abundant) and still happy to barbecue that last mammoth. In addition, humans showed up suddenly and acted too rapidly for the megafauna to evolve behavioral defenses - back in Africa, the human threat emerged slowly as humans gradually improved their cognitive skills and hunting prowess.
Temperature had been far lower _everywhere_ back at the glacial maximum: the Younger Dryas is a blip by comparison. No way climate did in the glyptodonts, gomphotheres, litopterns, toxodons, and sabertooths in South America: it was Injuns.
Asteroids are important - but they didn't wipe out the Pleistocene megafauna.
Probably the asteroids, alone, didn't it.
They could be the last straw that break the back of the camel.
Is there a time graph anywhere of estimated Paleoindian population, Amerindian population, megafauna population and climatic change?
There is oral and written history of major asteroid bombardments in North America starting at about 3,000 BCE.
GOING INTO THE WATER:
A SURVEY OF IMPACT EVENTS AND
THE COASTAL PEOPLES OF SOUTH-EAST NORTH AMERICA, THE CARIBBEAN, AND CENTRAL AMERICA
E.P. Grondine email@example.com
From the concluding text:
GOING INTO THE WATER
Well, there you have it: a worldview so absolutely different from our own that it has defied analysis for several hundred years by some of the best intellects available. It appears to me that the fundamental reason for this failure is that modern Europeans had not experienced impact events for a considerable period of time, and certainly nothing so devastating as the impacts the Maya experienced twice.
One of the most interesting aspects of this difference between peoples is their view of the afterlife. The Europeans retained but dim memories of the sky gods, and most peoples placed their afterlifes either in heaven, living comfortably with the sky gods, or in hell, consumed by the dimly remembered flames of a land impact. In contrast, the Maya had experienced a massive impact produced mega-tsunami, and they placed their afterworld under the sea, and described death as “going into the water”.
The differences are actually that great, and dealing with them has been exhausting. As for myself, this is simply as far as I am able to take this survey from hell for the indefinite future, a future in which I am looking forward to going into the water at some sandy beach. I plan to come back out of that water as well.
This is from the thread where I found the previous peice from:
POSSIBLE CHAIN OF METEORITE SCARS IN ARGENTINA
A string of linear depressions characterizes the Rio Cuarto crater field
In the January 16, 1992, issue of Nature, P.H. Schultz and R.E. Lianza describe a curious chain of grooves incised in the Argentine pampas near Rio Cuarto.
"During routine flights two years ago ..., one of us (R.E.L.) noticed an anomalous alignment of oblong rimmed depressions (4 km x 1 km) on the otherwise featureless farmland of the Pampas of Argentina. We argue here, from sample analysis and by analogy with laboratory experiments, that these structures resulted from lowangle impact and ricochet of a chondritic body originally 150-300 m in diameter."
There are ten gouges in all, strung out along 50 kilometers. The scars are young, perhaps only a few thousand years old, well within the time of human habitation. Schultz and Lianza also found pieces of meteoritic rock and glassy fragments of impact melt.
(Schultz, Peter H., and Lianza, Ruben E.; "Recent Grazing Impacts on the Earth Recorded in the Rio Cuarto Crater Field, Argentina," Nature, 355:234, 1992. Also: Monastersky, R.; "Meteorite Hopscotched across Argentina," Science News, 141:55, 1992.)
Comments. Note the similarities to the much more numerous Carolina Bays. See ETB1 in our catalog: Carolina Bays, Mima Mounds, Submarine Canyons.