Researchers have found the oldest DNA ever found, dating back more than a million years. The achievement marks a turning point in DNA research and shows that scientists now have the tools to research even more into the past than was once thought possible.
The DNA comes from the molar of three mammoth samples from the early and middle Pleistocene from northeastern Siberia, according to a study published Wednesday in the journal Nature. The main goal of the research project was genome sequencing before and after the origin and evolution of the other two branches.family tree, woolly and Colombian mammoths.
Based on the location of the specimens, preserved in permafrost and discovered in the 1970s, they were named Krestovka, Adycha and Chukochya. The mammoth from Krestovka is approximately 1.65 million years old, and Adycha is about 1.34 million years old. Chukochya is believed to be about 0.87 million years old one of the earliest known, the scientists said.
So far, the oldest DNA ever found belonged to a horse, and dates from 780,000 to 560,000 years ago.
Mammoth DNA recovery was not easy. “This DNA is extremely broken down into very small pieces, so we had to sequence many billions of ultrashort DNA sequences to confuse these genomes,” study lead author Love Dalén of the Stockholm Center for Paleogenetics said during a news briefing on Tuesday. “And this takes a lot of effort.”
Based on new specimens, scientists have determined that there were two mammoth vines in the region during the early Pleistocene. Adycha and Chukochya come directly from the line that eventually led to the woolly mammoth, while Krestovka represents a previously unknown lineage that researchers claim originated from the Colombian mammoth, which inhabited North America during the last ice age.
A comparison of the genomes of animals, in addition to their offspring, shed new light on the evolution of the species over time. There were significant differences between the Adycha and Chukochy molars – and newer woolly mammoths – in terms of enamel thickness, number and density of enamelled plates, and crown height, but it is not yet clear to scientists what factors are responsible for the changes.
Researchers hypothesize that the Krestovka lineage separated from the others approximately 2.66 to 1.78 million years ago, only to eventually migrate and 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 immediate ancestral relationship between really old genomes to younger genomes, it has allowed us to track evolution over time, and we could also track when certain adaptations through the Arctic environment may have evolved,” co-author Tom van der Said Walk on briefing. “And what we’ve found is that many of the adaptations we know have woolly mammoths, like 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 track changes in vines in many modern species. They stressed the importance of studying permanently frozen environments in order to further discover the ancient genetic data of the Earth.
“Our findings show that genomic data can be recovered from early Pleistocene samples, which opens up the possibility of studying adaptive evolution during speciation events,” the researchers said. “The mammoth genomes presented here provide insight into this potential.”