An international team of scientists led by researchers from the Stockholm Center for Paleogenetics (Sweden) has sequenced DNA recovered from mammoth remains (from three specimens) that are up to 1.2 million years old. It is the oldest DNA in the world.
Results from analysis of genetic material from ancient mammoth molars found in Siberia in the 1970s show that two distinct mammoth lineages were present in eastern Siberia during the early Pleistocene ; one of these lineages gave rise to the woolly mammoth ( Mammuthus primigenius ) and the other represents a previously unknown lineage that was ancestral to the first mammoths that colonized North America; the Columbian mammoth ( Mammuthus columbi ) traces its ancestry to a Middle Pleistocene hybridization between these two lineages.
The genetic material from ancient mammoth molars far exceeds the previous record set by 700,000-year-old DNA from a frozen, fossilized horse found in the Yukon permafrost.
“This DNA is incredibly old,” comments evolutionary geneticist Love Dalén of the Center for Paleogenetics in Sweden. “The samples are a thousand times older than Viking remains, and even predate the existence of humans and Neanderthals.”
According to the findings of the study, reported in the journal Nature , some mammoth gene fragments suggest that ancient mammoths already had the traits that allowed them to withstand cold temperatures during the last ice ages. The results also indicate that genetic variants associated with life in the Arctic, such as hair growth, thermoregulation, fat deposits, cold tolerance, and circadian rhythms, were already present in the million-year-old mammoth. , long before the origin of the woolly mammoth. Most of the adaptations in the mammoth lineage occurred slowly and gradually over time .
And it is that around a million years ago, a period in which many species expanded throughout the world, not even woolly mammoths still existed. It was also a period of great changes in climate and sea levels, as well as the last time the Earth’s magnetic poles changed places. And these beasts didn’t begin to emerge until about 800,000 years ago and became extinct about 4,000 years ago.
Thus, the oldest specimen belongs to a previously unknown mammoth genetic lineage, dubbed the Krestovka mammoth . Although researchers estimate that the oldest mammoth is 1.2 million years old (because of the age of the geologic section in which it was discovered), it could be even older, as mitochondrial genome data indicate that the specimen it could be up to 1.65 million years old; the second mammoth, named Adycha , could be 1.34 million years old and the last one, named Chukochya , 700,000 years old.
All previous studies have indicated that there was only one species of mammoth in Siberia at that time, called the steppe mammoth. But it is clear that we did not have all the information. “We can’t say for sure yet, but we think they may represent two different species ,” say the scientists.
“Being able to trace genetic changes through a speciation event is unique,” said Dr. David Díez-del-Molino, a researcher at the Swedish Museum of Natural History at Stockholm University and the Center for Paleogenetics. “Our analyzes show that most cold adaptations were already present in the woolly mammoth ancestor, and we found no evidence that natural selection was faster during the speciation process.”
Referencia: T. van der Valk et al. Million-year-old DNA sheds light on the genomic history of mammoths. Nature, published online February 17, 2021; doi: 10.1038/s41586-021-03224-9
