Frozen for ages: Ancient DNA reveals a lost Ice Age world

There is something quite magical about the idea of the time capsule. We imagine metallic containers buried underground in school yards full of letters and old coins. However, nature itself seems to have an even more devious trick up its sleeve, one that makes any of mankind’s innovations pale in comparison. For millennia, the planet has been running one of the largest experiments involving natural deep freezing anywhere in the Siberian tundra or the icy expanses of Greenland. The secrets of which have now begun to be unravelled by researchers only recently.It extends beyond fossils to include another scientific Holy Grail, the stuff of DNA itself. Scientists once thought it impossible for DNA to last even several hundred thousand years before breaking down completely, until a series of shocking discoveries proved that, under the right conditions, it could actually hang on for much, much longer than anyone imagined. As long as you can keep it cold enough, history isn’t lost forever.The million-year mammoth molar mysteryIn the search for the oldest DNA ever, a group of scientists began analysing mammoth molars buried in the ice in northeast Siberia. Not just any molars, but the oldest of their kind, dating from an age when the planet was entering a great freeze. It was an immense undertaking because so many years have passed, leaving behind only billions of fragments of DNA.A landmark 2021 report titled Million-year-old mammoth genomes shatter record for oldest ancient DNA revealed the fruits of this labour. By using cutting-edge laboratory techniques, scientists were able to sequence the genome of a mammoth that lived roughly 1.2 to 1.6 million years ago. This was a massive leap forward, nearly doubling the previous record for the oldest sequenced DNA. It allowed researchers to see exactly how these woolly giants evolved and adapted to the brutal cold of the Early Pleistocene.What makes the finding so fascinating is that it relies on actual physical specimens, authentic mammoth teeth meant for the chewing of tundra grass over a million years ago. What helped preserve the teeth in such good shape was that the permafrost slowed down their chemical decomposition, thus preserving genetic material. However, the task is extremely tricky. According to the researchers, the recovered fragments were highly deteriorated, and the process of obtaining them resembled reconstructing an entire one-million-page book from tiny fragments of paper.A two-million-year-old finding hidden in the earthIn addition to the above findings, there were still older discoveries lying within the permafrost of Greenland. This research stretched the timeline back to two million years ago. Unlike other findings discussed earlier, these did not involve any fossilised bones or teeth but relied on another technique, namely, environmental DNA.This breakthrough was detailed in the Nature study, A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA. By sampling ancient permafrost, researchers were able to reconstruct an entire vanished world. They found traces of mastodons, reindeer, and even various types of trees and shrubs that no longer grow in that part of the world. It showed that two million years ago, northern Greenland was much warmer and supported a lush, boreal forest teeming with life.The move from looking at bones to investigating the soil has turned the tables on all that we know. We no longer need to have a perfect set of bones before finding out what lived at one point in time in a certain area. The frozen lands of the Arctic turn into a book that keeps all its secrets hidden until the right tools are available to reveal them.Not only is this the most ancient DNA, but it also shows that Earth never forgets anything. Stored away in the tooth of a mammoth or preserved in the ice of its grains, history will be exhumed for inspection. They become time capsules, allowing us a glimpse into what our ancestors once knew.