By analyzing ancient DNA found in sediment, scientists can reconstruct past floras and explore long-standing historical questions, such as finding out where temperate trees survived during glacial stages. But despite the rapid progress in this field, scientists still face challenges when it comes to ancient DNA extraction, such as how to tackle inhibitors that may be present in the sediment and impede DNA sequencing.

Recently, a group of researchers in Canada developed a new cold spin inhibitor removal technique to extract ancient DNA from four permafrost samples from the Klondlike — a region in the Yukon territory in northwest Canada. This research was published in the Quaternary Research journal in September 2020.

Using this new technique, the researchers were able to overcome inhibitors present in sediment, allowing for a higher recovery of ancient DNA. 

The researchers also identified several animals and plants in their four permafrost samples, from as little as 0.2 grams of sediment, leading them to conclude that the samples belonged to different time points in the Pleistocene-Halocene transition, which occurred approximately 11,000 years ago. 

However, there were a few interesting anomalies. 

The researchers found genetic evidence suggesting that the woolly mammoth (Mammuthus primigenius) and horse (Equus sp.) may have survived longer than expected in the Klondike region, almost a thousand years later than previously thought. This adds to the conflicting evidence present. For example, while previous radiocarbon dating indicates that horses disappeared from North America relatively early (i.e. ~13,000 years ago), a 2009 study published in PNAS found ancient DNA evidence to suggest that woolly mammoths and horses persisted in interior Alaska until at least 10,500 years ago. 

While the mystery of the woolly mammoth and horse will need further investigation, this new study provides an alternative technique for scientists working with ancient DNA, rather than relying on the harsher treatments that destroy the very limited ancient DNA present in sediment.