A new study analyzing soil samples and DNA from Canada's permafrost has found evidence that woolly mammoths and Yukon wild horses may have survived thousands of years longer than previously thought.
The paper, published in the , compiled a 30,000-year DNA record of past environments, based on cored permafrost sediments taken from the Klondike region of central Yukon.
The researchers, who hail from McMaster University in Hamilton, Ont., the University of Alberta, the American Museum of Natural History and the Yukon government, say in a news release that their analysis reveals mammoths and horses were already in steep decline prior to the climatic instability of the Pleistocene-Holocene transition between 11,000 and 14,000 years ago, during which a number of large species such as mammoths, mastodons and sabre-toothed cats disappeared.
However, the researchers say mammoths and horses didn't immediately disappear as a result of overhunting by humans as previously believed.
Instead, they say the DNA evidence shows both the woolly mammoth and North American horse were around until as recently as 5,000 years ago during the mid-Holocene 鈥� the epoch humans currently live in, which began about 11,000 years ago.
The study builds on , who in 2020 reported that woolly mammoths and the North American horse were likely in the Yukon about 9,700 years ago.
"The rich data provides a unique window into the population dynamics of megafauna and nuances the discussion around their extinction through more subtle reconstructions of past ecosystems," said Hendrik Poinar, an evolutionary geneticist and lead author on the paper, who also serves as director of the McMaster Ancient DNA Centre.
Using tiny soil samples containing billions of microscopic genomic sequences from animal and plant species, as well as DNA capture-enrichment technology developed at McMaster, the researchers were able to reconstruct ancient ecosystems at different points in time during the Pleistocene-Holocene transition.
The researchers say the Yukon environment continued to experience massive change throughout the early Holocene, with formerly rich grasslands known as the "Mammoth Steppe" becoming overrun by shrubs and mosses.
Due in part to a lack of megafaunal "ecological engineers" such as large grazing herds of mammoths, horses and bison, grasslands no longer prosper in northern North America, according to a news release on the study.
"Now that we have these technologies, we realize how much life-history information is stored in permafrost," said Tyler Murchie, a postdoctoral researcher in McMaster's department of anthropology and a lead author of the study.
"The amount of genetic data in permafrost is quite enormous and really allows for a scale of ecosystem and evolutionary reconstruction that is unparalleled with other methods to date."
Co-author Ross MacPhee of the American Museum of Natural History added that while "mammoths are gone forever, horses are not."
"The horse that lived in the Yukon 5,000 years ago is directly related to the horse species we have today, Equus caballus. Biologically, this makes the horse a native North American mammal, and it should be treated as such."
Meanwhile, the researchers caution that permafrost is at risk of being lost forever as the Arctic warms, stressing the need to gather and archive more samples.
