Scientists have discovered the DNA of some 2,100 kinds of plants and 180 animals — including American horses and woolly mammoths – dating to thousands of years after their supposed extinction.
One of the most popular theories for the extinction of the wholly mammoth and other so-called ‘megafauna’ that was roaming during the Pleistocene is the claim that rapid global warming at the end of the last Ice Age killed off these giant species.
The idea that global warming rather ‘overkill’ by human hunters was chiefly responsible for the disappearance of the mammoth has gained in popularity in conjunction with claims that humans today are facing the same fate due to the same catastrophe.
Paleontologists have been arguing for decades what may have caused these species to vanish. For much of the second half of the 20th century the ‘overkill hypothesis’ dominated the scientific debate, claiming that the post-glacial expansion of human populations into their habitats led to the overhunting and gradual destruction of these species.
With the rise of climate catastrophism, a growing number of studies attempted to show that global warming rather than humans were primarily responsible for the disappearance of these Pleistocene species.
Now, a team of paleogeneticists have discovered DNA of “about 2,100 kinds of plants and 180 animals—including American horses and woolly mammoths, in samples from soil dated to thousands of years after their supposed extinction.”
Once this new discovery can be confirmed, the whole idea of an abrupt climate catastrophe wiping out the wholly mammoth and other Pleistocene species in one fell swoop is likely to go the way of the Dodo.
Ancient DNA preserved in soil may rewrite what we thought about the Ice Age
Based on bone and tooth records, the Yukon’s last mammoths were thought to have gone extinct about 12,000 years ago. But a new genetic sampling technique suggests the great beasts may have stuck around a lot longer, plodding through the Arctic tundra with bison and elk for thousands of years more. The story is in the soil.
Bones are rich sources of prehistoric genetic information, but not the only ones; items ranging from shed Ice Age skin cells to pine needles can contribute to the genetic record stored in dirt. Paleogeneticists have been extracting and analyzing “environmental DNA” from soil for a long time, but getting rid of non-DNA material without destroying these fragile clues is daunting.
“Environmental samples contain a huge range of other chemical substances that are challenging to separate from the DNA we’re interested in,” says McMaster University geneticist Tyler Murchie. “We can’t afford to lose whatever we can get.” In Quaternary Reports, Murchie and his colleagues describe gentler techniques that recover up to 59 times as much genetic material as other methods.
In the new approach, soil samples are extracted with a sterilized chisel and then broken into smaller portions, stirred and run through a “cold spin method” to separate as much DNA as possible. The DNA is then compared against an existing genetic library to detect species matches.
“Not only do these techniques get more DNA, but they get more diverse DNA,” says East Tennessee State University paleontologist Chris Widga, who was not involved in the new study. “It’s becoming more nuanced, and it looks like there is actually the potential to document larger slices of the ecosystem.”
This big picture comes from smaller samples, Murchie explains: “With a combination of our novel extraction and enrichment techniques, we can pull out entire genomes of multiple extinct organisms simultaneously from less than a gram of sediment.”
The methodology is limited because researchers using it need to know what DNA to look for. If a saber-toothed cat species is not already in the genetic library, for example, the analysis cannot detect that animal. For known species, however, the process may yield exciting information. In their study, the researchers detected about 2,100 kinds of plants and 180 animals—including American horses and woolly mammoths, in samples from soil dated to thousands of years after their supposed extinction.
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January 19, 2021 at 07:34AM
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