Researchers of the Center for Palaeogenetics at Stockholm have sequenced world’s oldest DNA from the molars of million-year-old mammoths. A study was published on the same in ‘Nature’ journal.
The research included three samples, two of them were more than a million-year old while one was around 800,000 years old, providing perception about the adaptation of mammoths to cold climate in Siberia. It was revealed that Columbian mammoth was a hybrid between woolly mammoth and earlier existing unknown genetic lineage of mammoth.
The analysis of the genomes of these three ancient mammoths, used DNA from their molars that were buried some 0.7-1.2 million years ago in the Siberian permafrost. Geological data and molecular clock both helped in the determination of the ages of these mammoths.
It was quite challenging to extract the DNA from these remains. It was also found out that only tiny amounts of DNA remained in the specimen while the rest got degraded into small fragments.
A professor of evolutionary genetics at Center for Palaeogenetics at Stockholm and senior author of the study published in Nature, Love Dalen said, “This DNA is incredibly old. The samples are a thousand times older than Viking remains, and even predate the existence of humans and Neanderthals.”
The remains of the Siberian mammoths were discovered in 1970s and were kept in the Russian Academy of Sciences in Moscow. The samples were geologically determined by comparing them with remains of some small rodents that were discovered in the sediment layers.
This revealed that the two mammoths were millions of years old steppe mammoths. And as stated earlier, the youngest of the three samples was a woolly mammoth.
Earlier, world’s oldest sequenced DNA was found in a horse existing some 780,000 to 560,000 years ago.
Genetic information was also extracted from minute samples of mammoths’ powdered teeth, “essentially like a pinch of salt you would put on your dinner plate,” said Dalen.
Small degraded fragments were sequenced forming tens of millions of chemical base pairs (essential components of DNA strands) and their age was determined through this genetic information.
Revelations were also made regarding the ages of world’s oldest mammoth, the Krestovka some 1.65 million years old, the second oldest Adycha is 1.34 million years old and the youngest Chukochya is 870,000 years old.
Geological evidence proved that the age of world’s oldest mammoth was some 1.2 million years, which varied from the data revealed through the DNA dating process maybe due to an undersestimation, said Dalen. However, there is a possibility that the sample was older, providing it had defrosted from Siberian permafrost and deposited in a younger sediment layer.
Lead author of the Science for Life Laboratory at Uppasala University, Tom van der walk said, DNA fragments were quite puzzling with millions of tiny pieces, “way, way, way smaller than you would get from a modern high-quality DNA.”
Reconstruction of mammoth genomes was done with the aid of genomes of an African elephant (a modern relative of mammoths) which served as a blueprint for algorithm.
There was an unnoticed genetic lineage in the Krestovka mammoth that is evaluated to diverge some 2 million years ago from mammoth species. They are the ancestors of the mammoths that inhabited North America.
Many other gene variants had hairiness, fat deposits, thermoregulation and cold tolerance in the earlier samples. This indicated that ancestors of woolly mammoths had hairiness.
Ice Age Mammoths:
Siberia has witnessed Ice age and undergone changes during the dry and cold Ice age conditions and warm, wet time intervals.
The increasing temperatures are melting the permafrosts and newer samples are discovered, however, remains could be washed out by increased rainfall, said Dalen. He added that advancing technologies would further make it possible to sequence older DNAs some 2.6 millions years back, from the remains in Siberian permafrost.
Curiosity of scientists may drive them into further researches on the ancestral species of moose, wolves, muskoxs and lemmings.
Journal Nature published the views of a professor in the Department of Animal Sciences at the University of Illinois, Alfred Roca, “Genomics has been pushed into deep time by the Giants of the Ice Age. The wee animals that surrounded them might soon also have their day.”