An article published in the journal “Nature” reports the sequencing of DNA fragments of some mammoth specimens even older than one million years. A team of researchers used advanced paleogenetic techniques to extract DNA from three teeth discovered in the 1970s, one from an early woolly mammoth and two assigned to the species it descended from, known as the steppe mammoth. These are the oldest genomes sequenced so far, and indicate among other things that the mammoth that inhabited North America during the last ice age was a hybrid between the woolly mammoth and mammoths belonging to a hitherto unknown genetic line. These findings offer new insights into the evolution of mammoths and their adaptation to cold climates.
The woolly mammoth (Mammuthus primigenius) is the most famous species of mammoth thanks to the fact that specimens arrived to us in an exceptional state of conservation because they were found frozen in Siberia. However, the history of mammoths is long and complex, also because it’s linked to the history of elephants, with which in some cases they interbred. The steppe mammoth (Mammuthus trogontherii) is considered the ancestor of the woolly mammoth and the first species of mammoth to have adapted to steppes and tundra to expand also in the American continent, also giving rise to the Colombian mammoth (Mammuthus columbi).
Dating techniques of the analyzed teeth indicate that their age varies between 700,000 and 1.2 million years, older than that of the bones from which it was possible to recover DNA fragments so far. However, in recent years, advances in sequencing techniques led to significant growth in the field of paleogenetics, the discipline that studies the DNA of extinct species. In this case, these are teeth that were very well preserved before being discovered by the Russian paleontologist Andrei Sher in the 1970s.
The result of this genetic analysis led to the sequencing of 49 million bases of DNA from the oldest tooth discovered near the village of Krestovka, 884 million bases of DNA from the tooth discovered in the Adycha River area, and 3,7 billion bases of DNA from the youngest tooth, that of a woolly mammoth discovered in the area of the city of Chukochya.
The analysis of the recovered DNA gave really interesting results regarding the history of these animals. The two oldest teeth were attributed to the steppe mammoth but show several genetic differences. The Adycha tooth indicates that the specimen belonged to the genetic line that gave rise to the woolly mammoth. The Krestovka tooth indicates that the specimen had some characteristics in common with the Colombian mammoth but also others belonging to a hitherto unknown genetic line of mammoths. This tooth could be as much as 1.6 million years old according to a genomic analysis.
The story that emerges from these teeth is fragmentary but sufficient to show that there were genetically different populations of mammoths that in some cases interbred. In places that have been very cold for a long time such as Siberia, it’s possible to discover very old bones and teeth where there are still pieces of DNA that can be sequenced. This study shows that even a tooth can offer valuable information on the history of an entire group of animals.