Researchers recover the oldest DNA ever found, from a mammoth more than 1 million years old

Researchers have recovered the oldest DNA ever found, dating back more than a million years. The achievement marks a milestone in DNA research and shows that scientists now have the tools to investigate even further back in history than was ever thought possible.

The DNA comes from the molars of three mammoth specimens from the early and middle Pleistocene period from northeastern Siberia, according to a study published Wednesday in the journal Nature. The main objective of the research effort was to sequence genomes before and after the origin and evolution of two other branches of the mammoth genealogical tree, woolly and Colombian mammoths.

Based on the location of the samples, preserved in permafrost and discovered in the 1970s, they have been named Krestovka, Adycha, and Chukochya. The Krestovka mammoth is approximately 1.65 million years old and Adycha is approximately 1.34 million years old. Chukochya, approximately 0.87 million years old, is believed to be one of the earliest known woolly mammothsthe scientists said.

Until now, the oldest DNA ever recovered belonged to a horse, dating from 780,000 to 560,000 years ago.

Retrieving DNA from mammoths was not easy. “This DNA was extremely degraded into very small pieces, so we had to sequence many billions of ultrashort DNA sequences to be able to decipher these genomes,” said lead study author Love Dalén of the Stockholm Center for Paleogenetics. he said during a press conference on Tuesday. “And it took a lot of effort to do this.”

Based on the new specimens, scientists have determined that there were two mammoth lineages in the region during the early Pleistocene. Adycha and Chukochya come directly from the line that ultimately led to the woolly mammoth, while Krestovka represents a previously unknown lineage that researchers say gave rise to the Columbian mammoth, which inhabited North America during the last Ice Age.

Comparing the genomes of animals, as well as their descendants, has shed new light on the evolution of the species over time. There were substantial differences between the Adycha and Chukochya molars, and the more recent woolly mammoths, in terms of enamel thickness, number and density of enamel plates, and crown heights, but scientists are still unclear which factors are responsible. of the changes.

Researchers hypothesize that the Krestovka lineage split from the others between 2.66 and 1.78 million years ago, eventually migrating to become the first North American mammoth. They concluded that the origin of the Colombian mammoth represents a “hybrid speciation event” between woolly mammoths and the Krestovka lineage.

“Because we have this direct ancestral relationship between the really old genomes and the younger genomes, this allowed us to track evolution over time, and we could track when certain adaptations across Arctic environments have possibly evolved,” co-author Tom van der. Valk said at the briefing. “And what we found is that many of the adaptations that we know woolly mammoths have, such as thermoregulation, changes in their circadian rhythm, fat deposits and hair growth, were already present” in the million-year-old mammoth.

The ability to extract ancient DNA from the early Pleistocene will now allow researchers to trace changes in the lineages of many modern species. They pointed out the importance of studying permanent frozen environments to further uncover Earth’s ancient genetic record.

“Our findings demonstrate that genomic data can be recovered from specimens from the early Pleistocene, opening the possibility of studying adaptive evolution through speciation events,” the researchers said. “The mammoth genomes presented here offer some insight into this potential.”