Oldest DNA discovery reveals new type of ancient animal
The new discovery is more than just the discovery of a long-missing family member: In one of three tusk samples discovered, scientists extracted the oldest DNA sample never found. It is estimated at 1.2 million years.
Why is this important – For researchers, this new discovery helps answer the question of how far can ancient DNA go before it degrades and is lost for history.
Since this DNA dates back 1.2 million years, researchers believe they could even find DNA as much as 2.6 million years in the future.
the research was published in the newspaper on Wednesday Nature.
“The samples are a a thousand times older than Viking remains, and even prior to the existence of humans and Neanderthals. “
Here is the background – Paleoarchaeologists and paleogeneticists are studying some of Earth’s oldest creatures, which means they are in a race against time when it comes to DNA degradation.
If it is not stored correctly, for example in ice permafrost, DNA will degrade over time. This means that genetic information may be insufficient to properly sequence some of Earth’s oldest fossils. Dinosaur DNA, for example, is usually lost in time.
Researchers have found these three mammoth molars buried under the permafrost in Siberia.
Prior to this study, the oldest DNA sequenced to date was discovered in 2013 and belonged to a ancient horse dating back to (a now picturesque) 560,000 to 780,000 years ago.
Among this oldest DNA sample, the researchers also discovered two other mammoth tusks that were over a million years old and around 700,000 years old, respectively.
What did they do – To analyze these three gigantic molars, the researchers used two different methods.
- They isolated short fragments of DNA that would have been better preserved by permafrost
- Use of a method called “biostratigraphy” to cross these faunal remains with faunal remains on sites with more absolute age data
- They used DNA dating from the mitochondria (known as the powerhouse of the cell) to estimate the age of the specimen
- They compared the ancient genomes of mammoths to those of modern Asian and African elephants to understand that different environmental adaptations may have evolved.
With all of this data combined, the researchers were able to construct a new sketch of the mammoth’s family tree.
What they discovered – A major discovery by the team was that the oldest specimen (nicknamed “Krestovka” for the site where it was found) represented a previously unknown mammoth line.
“All previous studies have indicated that there was only one species of mammoth in Siberia at that time, called the Steppe mammoth. But our DNA analyzes now show that there were two different genetic lines. We can’t say for sure yet, but we believe these may represent two different species. “
This new mammoth discovery also changes what scientists thought they knew about a subset of mammoths called the Colombian mammoth that roamed North America after the Ice Age. Instead of being a pure woolly mammoth, researchers are now speculating that the Colombian mammoth may in fact be a hybrid of the woolly lineage and Krestovka. (Critically, woolly mammoths are only a species of mammoth, although he is the most famous)
Through their analysis, the researchers also found that genetic adaptations associated with life in the Arctic (such as fat deposition, hair growth, and thermoregulation) were already present in the million-year-old mammoth. ‘years, long before woolly mammoths entered the scene.
And after – Researchers still don’t know much about this period in ancient history, but they are encouraged by these findings. The study suggests that the cut-off point for viable DNA analysis may be even further back than originally thought.
“One of the big questions now is how far back in time can we go?” Anders Götherström, professor of molecular archeology and co-director of research at the Center for Palaeogenetics, said in a statement.
“We haven’t hit the limit yet. An educated guess would be that we could recover DNA that is two million years old, and maybe even go back to 2.6 million.”
Abstract: Temporal genomic data have great potential for studying evolutionary processes such as speciation. However, sampling through speciation events would, in many cases, require genomic time series that go well back to the Lower Pleistocene sub-epoch. Although theoretical models suggest that DNA should survive this timescale, the oldest genomic data recovered to date comes from a horse specimen dated 780 to 560,000 years old. Here we report the recovery of genome-wide data from three mammoth specimens dating from the Lower and Middle Pleistocene sub-epochs, two of which are over one million years old. We find that two distinct lineages of mammoths were present in eastern Siberia during the Lower Pleistocene. One of these lines gave birth to the woolly mammoth and the other represents a hitherto unknown and ancestral line of the first mammoths to colonize North America. Our analyzes reveal that the Colombian mammoth from North America derives its ancestors from a Middle Pleistocene hybridization between these two lineages, with roughly equal mixing proportions. Finally, we show that the majority of protein coding changes associated with cold adaptation in woolly mammoths were already present a million years ago. These results highlight the potential of deep-time paleogenomics to expand our understanding of long-term speciation and adaptive evolution.