Researchers at McMaster University have developed a new technique for irritating ancient DNA from the soil by extracting the genomes of hundreds of animals and thousands of plants ̵
The method for extracting DNA described in the journal Quaternary research, allows scientists to reconstruct the most advanced picture of environments that existed thousands of years ago.
The researchers analyzed samples of permafrost from four places in the Yukon, each representing different points in the Pleistocene-Halocene transition that occurred about 11,000 years ago.
The transition involves the extinction of large numbers of animal species such as mammoths, mastodons and terrestrial sloths, and the new process has provided surprising new information on how events are unfolding, the researchers said. They suggest, for example, that the woolly mammoth survived far longer than originally thought.
In the Yukon samples, they found genetic remains of a huge number of animals, including mammoths, horses, bison, reindeer and thousands of plant species, all from just 0.2 grams of sediment.
Scientists have found that woolly mammoths and horses may still be present in the Klondike area of the Yukon as early as 9,700 years ago, thousands of years later than previous studies using fossils suggest.
“The fact that a few grams of soil contains the DNA of giant extinct animals and plants from another time and place allows a new kind of detective work to uncover our frozen past,” said evolutionary geneticist Hendrik Poinar, lead author of the paper and director of ancient DNA. McMaster Center. “This study allows us to maximize DNA retention and refine our understanding of change over time, which includes climatic events and patterns of human migration without preserved remains.”
The technique solves a long-standing problem for scientists who have to separate DNA from other substances mixed with sediment. The process usually requires harsh treatment, which actually destroys much of the used DNA they are looking for. But using the new combination of extraction strategies, McMaster researchers have demonstrated that it is possible to preserve much more DNA than ever before.
“All the DNA from these animals and plants is bound together in small patches of dirt,” explains Tyler Murchi, MD. candidate in the Department of Anthropology and lead author of the study.
“Organisms constantly shed cells throughout their lives. Humans, for example, shed about half a billion skin cells every day. Much of this genetic material is rapidly degraded, but some small fractions are protected for millennia by sedimentary binding of minerals and go out there. We are waiting to recover and study it. Now we can do some remarkable research, recovering a huge variety of environmental DNA from very small amounts of sediment and in the complete absence of surviving biological tissues. ”
Mastodons often traveled north when the climate changed
Tyler J. Murchi et al., Optimizing the extraction and targeted capture of ancient DNA from the environment to recover past environments using the PalaeoChip Arctic-1.0 bait kit, Quaternary research (2020). DOI: 10.1017 / to.2020.59
Provided by McMaster University
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