Researchers have compiled the oldest known DNA in the world. Using material from the early and middle Pleistocene period, ancient DNA analysis breaks the record of the world’s oldest DNA in sequence. It comes from giant remains discovered in the Siberian permafrost, and it proves that ancient DNA under the right conditions can survived more than one million years.
But the analysis of that very old DNA depends on researchers also having the right technology. Fortunately, an international team led by researchers from the Center for Paleogenetics in Stockholm, Sweden, has advanced sequence technology and bioinformatics at their disposal. A Nature in the news report for the new newspaper, it is said that the researchers pushed the current technology almost to its extreme to extract old DNA strands from giant teeth preserved in the Siberian permafrost. Senior author of the Nature study, Love Dalén, a professor of evolutionary genetics at the Center for Paleogenetics, notes that the scientific team was happy and said:
‘It’s not as if everything in the permafrost always works. The vast majority of samples have shit DNA. ”
How the ancient mammoth DNA records
The discovery is really surprising, because after an organism dies, the chromosomes gradually get smaller, and in most cases, extremely old DNA strands are so small that they have lost all their information. But a new article published in the magazine Nature shows that the team managed to obtain 49 million base pairs of nuclear DNA from a 1.65 million year old tooth found near a town called Krestovka (the tooth was also called Krestovka). They also extracted 884 million base pairs of ancient DNA from a 1.3 million year old tooth they call Adycha and 3.7 billion base pairs of DNA from a 600,000 year old woolly tooth they named Chukochya. The three giant remains were discovered in the 1970s and form part of the collection of the Russian Academy of Sciences in Moscow.
Love Dalén and co-lead author Patrícia Pečnerová with a giant canine on Wrangel Island. (Credit: Gleb Danilov)
The Nature news report explains that the ancient mammoth DNA study did not discover the oldest biomolecular information from the fossil record – these are proteins that were followed in 2016 from 3.8 million year old ostrich eggshells from Tanzania. Second is a protein sequence from a 1.77 million-year-old rhino tooth from Georgia, which was analyzed in 2019. Although proteins are harder and can survive in very old fossils from places without permafrost, they are not as useful as DNA for researchers who want to study the ancestry of an organism.
This is just one of the reasons why the new mammoth DNA study is so important: it contains genetic information that was not available in the older protein samples.
A second reason why the study is making headlines is that it struck ancient DNA of a genome from a 560,000 to 780,000 year old horse’s bone found in the Yukon region of Canada for the oldest ancient DNA sequence. To put the age of mammoth monsters in context, Dalén said:
‘This DNA is incredibly old. The monsters are a thousand times older than the remains of Viking and even pre-date the existence of humans and Neanderthal people. ”
The first example of hybrid speciation in ancient DNA
The new study also increased the ability of researchers to track the evolutionary process of speciation – the formation of new and different species. A Nature press release states that this process usually takes place “over periods considered outside the bounds of DNA research.”
A tooth from a woolly mammoth discovered in 2017 in a creek bed on Wrangel Island. (Credit: Love Dalén)
Nevertheless, the scientists’ study of the mammoth DNA indicates that not one, but two different generations of mammoths were alive during the early Pleistocene in the area of what is now Eastern Siberia. Adycha and Chukochya are believed to be members of a species that produced the woolly mammoth, but Krestovka apparently comes from an unknown, and possibly completely new, mammoth lineage. Tom van der Valk, the lead author of the study and a bioinformatics scientist at Uppsala University in Sweden, explains the researchers’ shock at this discovery:
“It was a complete surprise for us. All previous studies indicated that at that time there was only one species of mammoth in Siberia, the steppe mammoth. But from our DNA analyzes it appears that there were two different genetic descendants, which we refer to here as the Adycha mammoth and the Krestovka mammoth. We can not yet say with certainty, but we think it may represent two different kinds. ”
In their study, the researchers suggest that the Krestovka genome deviated from the other mammoths between 2.66 and 1.78 million years ago. They also believe that this giant tribe ‘was from ancestors to the first mammoths that colonized North America’. It turns out that the North American Columbian mammoths ( Mammuthus columbi ) can trace half of their ancestry to woolly mammoths and half to the previously unknown Krestovka mammoth lineage.
The Nature news report states that this means that the new study also provided the first evidence for ‘hybrid speciation’ – a new species formed by mixing – found in ancient DNA. Study co-author Patrícia Pečnerová, an evolutionary biologist at the Swedish Museum of Natural History, says the team believes’ that the Columbia mammoth, one of the most iconic ice age species in North America, evolved by a hybridization of about 420 thousand. years ago. ”
How far can researchers go?
Finally, the ancient giant DNA study inspired Dalén to analyze more permafrost animals that are more than a million years old. Next on his list? Musk oxen, elk and lemmings. But the professor of evolutionary genetics knows that there is an age limit he will not be able to exceed if he analyzes the ancient DNA – 2.6 million years – ‘This is the limit of the permafrost. Before that it was too hot, ”he says.
Volumetric tusk emerging from permafrost on Central Wrangel Island in northeastern Siberia. (Credit: Love Dalén)
Top image: the illustration represents a reconstruction of the steppe mammoths that preceded the woolly mammoth, based on the genetic knowledge we now have of the Adycha mammoth. Source: Beth Zaiken / Center for Paleogenetics
By Alicia McDermott