Researchers at McMaster University have developed a new technique to tease ancient DNA from soil, pulling the genomes of hundreds of animals and thousands of plants which many of them are long extinct.
The DNA extraction method, outlined in the journal Quarternary Research, allows scientists to reconstruct the most advanced picture ever of environments that existed thousands of years ago.
According to a report published by the University of McMaster, this technique retrieves the ancient DNA by using the cells constantly shed by organisms throughout their lives.
"Organisms are constantly shedding cells throughout their lives. Humans, for example, shed some half a billion skin cells every day. Much of this genetic material is quickly degraded, but some small fraction is safeguarded for millennia through sedimentary mineral-binding and is out there waiting for us to recover and study it. Now, we can conduct some remarkable research by recovering an immense diversity of environmental DNA from very small amounts of sediment, and in the total absence of any surviving biological tissues," explained evolutionary geneticist Hendrik Poinar, a lead author on the paper.
The researchers used their technique to analyze soil samples from four sites in the Yukon region, each representing different points in the Pleistocene-Halocene transition, which occurred approximately 11,000 years ago.
This transition featured the extinction of a large number of animal species such as mammoths, mastodons and ground sloths, and the new process has yielded some surprising new information about the way events unfolded.
"In the Yukon samples, we found the genetic remnants of a vast array of animals, including mammoths, horses, bison, reindeer and thousands of varieties of plants. The scientists determined that woolly mammoths and horses were likely still present in the Yukon's Klondike region as recently as 9,700 years ago, thousands of years later than previous research using fossilized remains had suggested," Poinar said.