Groundbreaking research into incredibly ancient DNA that predates even the longest human timelines has set new records, unlocking the evolutionary secrets of the long-extinct mammoth. The DNA was taken from mammoth remains up to 1.2 million years old, allowing researchers to peer back through time to understand how climate adaptations took place and in the process identify what appears to be a new species.
DNA sequencing is relatively new, but some of the samples that scientists have analyzed have been around a very long time. Until now, the oldest DNA sample to be recovered and have its genome sequenced was from a horse that lived potentially 700,000 years ago. That was back in 2013.
Now, though, a team led by researchers at the Centre for Palaeogenetics at Stockholm University have looked at mammoth remains up to 1.2 million years go.
Love Dalén, a Professor of evolutionary genetics at the Centre, and senior author on the new study said, the samples are a thousand times older than Viking remains and even pre-date the existence of humans and Neanderthals.
The genomes of three ancient mammoths was analyzed from DNA extracted from teeth discovered buried in Siberian permafrost. Predating wooly and Columbian mammoths, each yet to evolve, they were from the period of the steppe mammoth which lived during the late Early and Middle Pleistocene, roughly 1.7 million-200,000 years ago. Known to have grown to around 13 feet to the shoulders, the males had spiral tusks that could grow up to 16 feet in length.
The oldest of the three specimens, however, unlocked a surprise. Unlike the others, it came from a different, distinct genetic lineage that’s now been named the Krestovka mammoth, after the location the tooth was found in. According to the genome analysis, it diverged from other Siberian mammoths in excess of two million years ago.
Tom van der Valk, lead author of the study said, this came as a complete surprise to us. All previous studies have indicated that there was only one species of mammoth in Siberia at that point in time, called the steppe mammoth. But our DNA analyses now show that there were two different genetic lineages, which we here refer to as the Adycha mammoth and the Krestovka mammoth. We can’t say for sure yet, but we think these may represent two different species.
While a new, extinct species is interesting enough, what makes the Krestovka mammoth particularly special is how it helps understand the colonization of North America by the animals. The new theory is that Krestovka lineage mammoths not only came to North America roughly 1.5 million years ago, but also contributed half of the genome later found in the Columbian mammoth. That Ice Age species had previously been thought to descend solely from the woolly mammoth.
In the process, it helps understand just how the Columbian mammoth survived in the extreme cold conditions. Survival factors like hair growth, thermoregulation, fat deposits, cold tolerance, and certain circadian rhythms were passed down from older mammoth lineages. That meant the rapid evolutionary explanation scientists had previously looked to in order to explain mammoth cold adaptations need not in fact be required.
Although the newly-sequenced genome sets a fresh record, scientists are still confident that much deeper trawls through historic DNA are possible though only up to a point.
Anders Götherström, a professor in molecular archaeology and joint research leader at the Centre for Palaeogenetics said, one of the big questions now is how far back in time we can go. We haven’t reached the limit yet. An educated guess would be that we could recover DNA that is two million years old, and possibly go even as far back as 2.6 million. Before that, there was no permafrost where ancient DNA could have been preserved.