"A marvellous forgetfulness of the former destruction would appear to have come over them." -- Plato, philosopher, Laws: Book III, 360 B.C.
Science Daily: Mass Extinction: Why Did Half of N. America's Large Mammals Disappear 40,000 to 10,000 Years Ago?
ScienceDaily (Nov. 27, 2009) — Years of scientific debate over the extinction of ancient species in North America have yielded many theories. However, new findings from J. Tyler Faith, GW Ph.D. candidate in the hominid paleobiology doctoral program, and Todd Surovell, associate professor of anthropology at the University of Wyoming, reveal that a mass extinction occurred in a geological instant.A "geological instant" doesn't sound "slow and gradual" to me: Catastrophism 1-Uniformitarianism 0.
Here is the actual data which scientists deliberately choose to ignore because it contradicts their childish religions:
PNAS (Oct 07): Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.
A carbon-rich black layer, dating to ≈12.9 ka, has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka.New Scientist (May 07): Firestorm from space wiped out prehistoric Americans.
THE Clovis people of North America, flourishing some 13,000 years ago, had a mastery of stone weaponry that stood them in good stead against the constant threat of large carnivores, such as American lions and giant short-faced bears. It's unlikely, however, that they thought death would come from the sky.New Scientist (Dec 07): Ancient flood brought Gulf Stream to a halt .
According to results presented by a team of 25 researchers this week at the American Geophysical Union meeting in Acapulco, Mexico, that's where the Clovis people's doom came from. Citing several lines of evidence, the team suggests that a wayward comet hurtled into Earth's atmosphere around 12,900 years ago, fractured into pieces and exploded in giant fireballs. Debris seems to have settled as far afield as Europe.
Jim Kennett, an oceanographer at the University of California, Santa Barbara, and one of the team's three principal investigators, claims immense wildfires scorched North America in the aftermath, killing large populations of mammals
It was the biggest climate event of the last 10,000 years and caused the most dramatic change in the weather since humans began farming. And it may yet hold important lessons about climate change in the 21st century.Science (Jan 09): Nanodiamonds in the Younger Dryas Boundary Sediment Layer.
Just over 8000 years ago, a huge glacial lake in Canada burst, and an estimated 100,000 cubic kilometres of fresh water rushed into the North Atlantic. Researchers now say they know for sure that this catastrophic event shut down the Gulf Stream and cooled parts of the northern hemisphere by several degrees for more than a hundred years.
They say the findings show modelling studies are right to suggest that something similar could happen with equal abruptness
We report abundant nanodiamonds in sediments dating to 12.9 ± 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.National Geographic (Jan 09): Diamonds Link Comets to Killer Freeze 13,000 Years Ago.
Diamond dust found in 12,900-year-old sediments at six North American sites boosts evidence of Earth's impact with a swarm of comets at that time, researchers reported today.Washington Post (Jan 09): Gems Point to Comet as Answer to Ancient Riddle.
The discovery supports the theory that an impact with an extraterrestrial object may have contributed to the disappearance of large mammals and the Clovis culture of prehistoric humans, the scientists say.
Scientists proposed in 2007 that a cosmic impact, 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.
In today's issue of the journal Science, a team led by the University of Oregon's Douglas J. Kennett, a member of the 2007 research team, reports finding billions of microscopic-size diamonds in sediments in the six locations (see map below) during digs funded by the National Science Foundation.
"The nanodiamonds that we found at all six locations exist only in sediments associated with the Younger Dryas Boundary layers, not above it or below it," said Kennett, a University of Oregon archaeologist, in a university press release.
Kennett and colleagues say the only obvious explanation for the concentration of nanodiamonds (seen in the image on the left) is that they were created in the high-energy environment of an impact by a comet or other extraterrestrial object.
"These discoveries provide strong evidence for a cosmic impact event at approximately 12,900 years ago that would have had enormous environmental consequences for plants, animals and humans across North America."
Something dramatic happened about 12,900 years ago, and the continent of North America was never the same. A thriving culture of Paleo-Americans, known as the Clovis people, vanished seemingly overnight. Gone, too, were most of the largest animals: horses, camels, lions, mammoths, mastodons, saber-toothed cats, ground sloths and giant armadillos.
Scientists have long blamed climate change for the extinctions, for it was 12,900 years ago that the planet's emergence from the Ice Age came to a halt, reverting to glacial conditions for 1,500 years, an epoch known as the Younger Dryas.
In just the last few years, there has arisen a controversial scientific hypothesis to explain this chain of events, and it involves an extraterrestrial calamity: a comet, broken into fragments, turning the sky ablaze, sending a shock wave across the landscape and scorching forests, creatures, people and anything exposed to the heavenly fire.
Now the proponents of this apocalyptic scenario say they have found a new line of evidence: nanodiamonds. They say they have found these tiny structures across North America in sediments from 12,900 years ago, and they argue that the diamonds had to have been formed by a high-temperature, high-pressure event, such as a cometary impact.