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Why 1.7 million-year-old rhino tooth will prompt evolution revolution after Cambridge and Copenhagen study

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Scientists have extracted the oldest genetic data recorded so far - from a 1.77 million-year-old rhino tooth.

The findings by scientists at St John’s College, Cambridge, and the University of Copenhagen, and the technique they used, are predicted to kick-start an evolution revolution.

They identified an almost complete set of proteins - a proteome - in the dental enamel of the rhino.

Stephanorhinus skull from Dmanisi. Picture: Mirian Kiladze, Georgian National Museum (16702724)
Stephanorhinus skull from Dmanisi. Picture: Mirian Kiladze, Georgian National Museum (16702724)

The genetic information discovered is a million years older than the oldest DNA sequenced to date, which came from a 700,000-year-old horse.

Published in Nature, the study marks a breakthrough in the field of ancient biomolecular studies. By allowing scientists to reconstruct evolution from further back in time, it could solve some of the mysteries of animal and human biology.

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.”

The lineages that led to modern humans and our closest living relatives, the chimp, branched apart around six to seven million years ago.

But DNA data tracking human evolution only covers the last 400,000 year, meaning we currently have no genetic information for more than 90 per cent of the evolutionary path leading to the modern human.

The genetic links between us and extinct species such as Homo erectus – the oldest known species of human with body proportions like ours - are unknown, with is almost all our evidence based exclusively on anatomical details only.

But now researchers have used ancient protein sequencing, using mass spectrometry technology, to retrieve the genetic information from the tooth of a Stephanorhinus, an extinct rhinoceros that lived in Eurasia during the Pleistocene.

The ancient fossil was discovered in Dmanisi, Georgia, and researchers took from it samples of dental enamel - the hardest material present in mammals - before applying mass spectrometry to sequence the ancient protein. This retrieved the genetic information previously unobtainable using DNA testing.

Left lower Stephanorhinus molar from Dmanisi. Picture: Natural History Museum of Denmark (16702726)
Left lower Stephanorhinus molar from Dmanisi. Picture: Natural History Museum of Denmark (16702726)

The study showed the set of proteins the enamel contains lasts longer than DNA and is more genetically informative than collagen, which is the only other protein retrieved from fossils more than one million years old.

Professor Jesper V Olsen, head of the mass spectrometry for quantitative proteomics group at the Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, and co-corresponding author on the paper, said: “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.

“It is the only technology able to provide the robustness and accuracy needed to sequence tiny amounts of protein this old.”

Lead author Professor Eske Willerslev, who holds positions at St John’s College, University of Cambridge, and is director of The Lundbeck Foundation Centre for GeoGenetics, Globe Institute, Faculty of Health and Medical Sciences, at the University of Copenhagen, said: “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. It will revolutionise the methods of investigating evolution based on molecular markers and it will open a complete new field of ancient biomolecular studies.”

Professor Cappellini added: “Dental enamel is extremely abundant and it is incredibly durable, which is why a high proportion of fossil records are teeth.

“We have been able to find a way to retrieve genetic information that is more informative and older than any other source before, and it’s from a source that is abundant in the fossil records so the potential of the application of this approach is extensive.”

The researchers believe identifying changes in numerous extinct mammals and humans could lead to major shifts in our understanding of the way the world has evolved.

By collecting the genetic data of ancient fossils, scientists could build a more accurate picture of the evolution of hundreds of species, including our own.

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