Recently, researchers used DNA capture-enrichment technology to present a 30,000-year sedaDNA record derived from preserved permafrost silts in Canada. They identified a lingering signal of the woolly mammoth persisting thousands of years after their supposed extinction from the fossil record.
The Pleistocene-Holocene transition took place around 11,000 years ago. It caused the extinction of many fauna species, including more than 100 genera of the Earth’s largest terrestrial animals at the time. One such example is the woolly mammoth (Mammuthus primigenius). This loss is thought to have restructured the terrestrial biosphere, impacting vegetation composition, biogeochemistry and climate feedback systems. There is speculation as to whether these shifts were because of the direct result of rapid climate change, or whether the dispersal of Homo sapiens, a new predator, was to blame.
Advances in the extraction and identification of ancient DNA, which has been shed into the environment and preserved for millennia in sediment, is now providing a way to explore these palaeontological queries. Sedimentary ancient DNA (sedaDNA) is increasingly being used to study past ecosystems. The advantage of using sedaDNA is that it is able to detect genetic signals of taxa that do and don’t fossilise. This means that, in theory, it is possible to go beyond standard environmental proxies and facilitate reconstruction of past ecosystems across the entire food web.
When did the woolly mammoth really go extinct?
Recently, researchers from McMaster University, the University of Alberta, the American Museum of Natural History and the Yukon government used DNA capture-enrichment technology to investigate the fluctuating animal and plant communities throughout the Pleistocene-Holocene transition. They presented a 30,000-year sedaDNA record derived from preserved permafrost silts in the Klondike region of Yukon, Canada, and published their results in Nature Communications.
The team observed a substantial turnover in ecosystem composition between 13,500-10,000 years ago, with the rise of woody shrubs and the disappearance of the steppe-tundra ecosystem. Previously, this biome covered wide areas of the northern part of the globe and thrived for approximately 100,000 years without major changes. Additionally, the researchers identified a lingering signal of the woolly mammoth at multiple sites persisting thousands of years after their supposed extinction from the fossil record.
How accurate is sedaDNA?
It’s certainly exciting that just a spoonful of soil pulled from the permafrost is able to open such vast windows into ancient life and potentially re-write previous beliefs about the extinction of such an iconic creature, like the woolly mammoth. But it’s difficult to say whether sedaDNA signal decay reflects an actual reduction in the regional abundance of animals or is reflective of other stochastic and unknown factors.
Hendrik Poinar, a lead author in the paper, said:
“The rich data provides a unique window into the population dynamics of megafuana and nuances the discussion around their extinction through more subtle reconstructions of past ecosystems.”
Image credit: ABC Columbia
