Researchers identified an almost complete set of proteins, a proteome, in the dental enamel of the rhino and the genetic information discovered is one million years older than the oldest DNA sequenced from a 700,000-year-old horse.
The findings by scientists from the University of Copenhagen and St John’s College, University of Cambridge, are published in Nature. They mark a breakthrough in the field of ancient biomolecular studies and could solve some of the biggest mysteries of animal and human biology by allowing scientists to accurately reconstruct evolution from further back in time than ever before.
Professor Enrico Cappellini, a specialist in Palaeoproteomics at the Globe Institute, University of Copenhagen, and first author on the paper, said: “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. 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."
DNA data that genetically tracks human evolution only covers the last 400,000 years. But the lineages that led to modern humans and to the chimp – the living species genetically closest to humans – branched apart around six to seven million years ago which means scientists currently have no genetic information for more than 90 per cent of the evolutionary path that led to modern humans.
Scientists also don’t know what the genetic links are between us and extinct species such as Homo erectus – the oldest known species of human to have had modern human-like body proportions – because everything that is currently known is almost exclusively based on anatomical information, not genetic information.
Researchers have now used ancient protein sequencing – based on ground-breaking technology called mass spectrometry – to retrieve genetic information from the tooth of a 1.77 million year old Stephanorhinus – an extinct rhinoceros which lived in Eurasia during the Pleistocene. Researchers took samples of dental enamel from the ancient fossil which was discovered in Dmanisi, Georgia, and used mass spectrometry to sequence the ancient protein and retrieved genetic information previously unobtainable using DNA testing.
Tooth enamel is the hardest material present in mammals. In this study researchers discovered the set of proteins it contains lasts longer than DNA and is more genetically informative than collagen, the only other protein so far retrieved from fossils older than one million years.
Image: Stephanorhinus skull from Dmanisi
Credit: Mirian Kiladze, Georgian National Museum
Reproduced courtesy of the University of Cambridge