Researchers have discovered 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 tools even further back in history than they thought possible.
The DNA comes from the molecules of three raspberry samples from the Early and Middle Pleistocene period of northeastern Siberia, according to a study published Wednesday in the journal Nature. The main aim of the research effort was to classify genomes from before and after the origin and evolution of two other branches of the mammoth family tree, woolly mammals and Columbian.
Based on the locations of the samples, preserved in permafrost and discovered in the 1970s, they were named Krestovka, Adycha and Chukochya. Krestovka’s mammoth is about 1.65 million years old and Adycha is about 1.34 million years old. Chukochya, at the age of 0.87 million years, is believed to be one of the earliest known wool mammals, said the experts.
To date, the oldest DNA ever found belonged to a horse, dating from 780,000 to 560,000 years ago.
Mammal DNA was not easy to recover. “This DNA was greatly reduced in very small pieces, so we had to sequence a series of billions of ultra-short DNA sequences, to mimic these genomes together,” said the study’s lead author, Love Dalén of the Center for Palaeogenetics in Stockholm, said at a press conference Tuesday. “And he put a lot of effort into doing this.”
Beth Zaiken / Palaeogenetics Center
Based on the new samples, scientists have confirmed that there were two raspberry lines in the area during the Early Pleistocene. Adycha and Chukochya descend directly from the line that caused the last wool mamma, while Krestovka represents an previously unknown line suggested by researchers that produced the Columbian mammal. , who lived in North America during the last Ice Age.
By comparing the genomes of the animals, as well as their offspring, they have shed new light on the evolution of the species over time. Adycha’s molars and Chukochya’s – and more recent woolly mammals – differed widely in enamel thickness, number and density of enamel blades and crown height, but it is not yet clear to scientists what factors are present. depending on the changes.
Researchers consider the Krestovka line away from the others around 2.66 to 1.78 million years ago, eventually migrating to become the first North American mammoth. They concluded that the origin of the Columbian raspberry represents a “hybrid profiteering event” between woolly mammals and the Krestovka line.
Gleb Danilov
“Because we have this direct ancestral relationship between the old genomes to the younger genomes, this allowed us to trace evolution over time, and we were able to hold back traces where changes may occur. particular through the evolving Arctic environments, “co – author Tom van der Valk said at the meeting.” And what we found was that many of the changes that we know of that woolly mammals, such as thermoregulation, changes in their circadian rhythm, fat deposits and hair growth, are already present “in the million-year-old mammal.
The ability to extract ancient DNA from the Early Pleistocene now allows researchers to track changes in sequences across many modern species. They noted the importance of studying permanent frozen environments to find out the Earth ‘s ancient genetic record.
“Our findings show that genomic data can be retrieved from Early Pleistocene samples, which opens up the possibility of studying variable evolution across profiteering events,” researchers said. The mammoth genomes presented here give us an insight into this potential. ”