A group of researchers extracted genetic information from a 1.77 million-year-old rhino tooth—the largest genetic data set this old to ever be confidently recorded. They identified an almost complete set of proteins, a proteome, in the dental enamel of the now-extinct rhino.
The findings mark a breakthrough in the field of ancient molecular studies and could solve some of the biggest mysteries of ancient animal and human biology by allowing scientists to accurately reconstruct evolution from further back in time than ever before.
The genetic information discovered is one million years older than the oldest DNA sequenced, which came 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 the journal 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 Professor Enrico Cappellini. “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.”
Human evolution that is tracked by DNA only covers the last 400,000 years. But the lineages that led to modern humans and to the chimpanzee branched apart around six to seven million years ago. This means scientists currently have no genetic information for more than 90% of the evolutionary path that led to modern humans.
Researchers also do not 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. As things stand, everything that is known is based almost exclusively on anatomical and not genetic information.
In this new study, the team used ancient protein sequencing – based on groundbreaking technology called mass spectrometry – to retrieve genetic information from the tooth. They took samples of dental enamel from the ancient fossil, which was discovered in Dmanisi, Georgia.
Mass spectrometry was used to sequence the ancient protein and retrieved genetic information previously unobtainable using DNA testing. Tooth enamel is the hardest material present in mammals, and the set of proteins it contains lasts longer than DNA and is more genetically informative than collagen, scientists 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 revolutionize the methods of investigating evolution based on molecular markers and it will open a completely new field of ancient biomolecular studies, said professor Eske Willerslev.
