Between 2.5 million and 700,000 years ago, a now-extinct group of rhinos known as Stephanorhinus stomped across northern Eurasia. Now, game-changing research has extracted genetic information from the 1.7-million-year-old tooth of one of these ancient beasts. Not only is it the oldest genetic data to ever be recorded, but it could also pave the way for research into how mammals, including us, have evolved over millions of years.
The genetic information was preserved in the enamel of the rhino’s tooth. Enamel can be a useful tool for palaeontologists as it's the hardest material found in the mammalian body and therefore highly durable. Before this study came along, the oldest genetic information sequenced from an animal came in the form of DNA from a 700,000-year-old horse. The new findings are reported in Nature.
"For 20 years ancient DNA has been used to address questions about the evolution of extinct species, adaptation and human migration but it has limitations,” said first author Enrico Cappellini, a professor at the University of Copenhagen, in a statement. “Now for the first time we have retrieved ancient genetic information which allows us to reconstruct molecular evolution way beyond the usual time limit of DNA preservation.
"This new analysis of ancient proteins from dental enamel will start an exciting new chapter in the study of molecular evolution."
The fossilized tooth was discovered in Dmanisi, Georgia, and analyzed using a technique called mass spectrometry. This allowed the researchers to obtain genetic information that would not be extractable using standard DNA tests. They identified an almost complete proteome, the set of proteins expressed by the tissue, and found it to be longer lasting than DNA and more genetically informative than collagen, the only other protein to be obtained from fossils dating back more than a million years.
“Mass spectrometry-based protein sequencing will enable us to retrieve reliable and rich genetic information from mammal fossils that are millions of years old, rather than just thousands of years old,” explained co-corresponding author Professor Jesper V. Olsen. “It is the only technology able to provide the robustness and accuracy needed to sequence tiny amounts of protein this old."
The ability to remove genetic information from fossils dating back millions of years could have exciting applications when it comes to understanding our own family tree. Right now, we’re lacking genetic information for over 90 percent of our evolutionary history; the DNA we do have only goes back 400,000 years, but we branched away from chimpanzees as long as 7 million years ago. Being able to sequence genetic information from our very ancient ancestors could fill in some gaps about how Homo sapiens eventually came to be.
"This research is a game-changer that opens up a lot of options for further evolutionary study in terms of humans as well as mammals,” said lead author Professor Eske Willerslev of the University of Cambridge. “It will revolutionise the methods of investigating evolution based on molecular markers and it will open a complete new field of ancient biomolecular studies."