Scientists have sequenced the oldest known genome in a 700,000-year-old horse, they came up with a shockingly detailed picture of the prehistoric creature's DNA.
The horse had been frozen for thousands of years in the permafrost of Yukon, Canada, according to a University of Copenhagen press release. The researchers tracked the genomic changes by sequencing short strands of DNA from the ancient horse to get a clear idea of the animal's DNA. Scientists have used this method to map the DNA of some ancient hominids, but none have been as old.
The team compared the genome with samples from a 43,000-year-old horse, six modern horse breeds, and a donkey. They were able to determine how "fast mutations accumulate through time and calibrate a genome-wide mutation rate."
Taking cues from the new information, they concluded the oldest common horse ancestor walked the Earth about 4.5 million years ago, which is twice as long ago as was originally thought. The findings also help to explain the distinct physical differences, and mysterious extra chromosomes, differentiating the modern Przewalski's Horse from other breeds.
The team was able to pinpoint the genetic mutations which caused the unique horse to isolate from its common lineage 500,000 years ago. The scientists found DNA in the ancient horse's blood proteins, a substance rarely found in fossils.
A technique called Helicos true Single DNA Molecule Sequencing was used to find molecular preservation niches in the bone, which allowed the team to create a full genome.
"Because [of] 700,000 years of evolution and damage, it is not something that does come without any modification to the DNA sequence itself. We had to improve our ability to identify modified and divergent ancient horse sequences by aligning them to the genome of present day horses." said Dr. Ludovic Orlando, who was a leader of the study. "Quite a computational challenge, especially when the level of DNA modification outcompasses that seen in any other Arctic horses from the Late Pleistocene."
The study gives hope for finding out even more about our ancient ancestor's DNA and could allow us to look even further into the past.
"The results of the studies and the applied techniques open up new doors for the exploration of prehistoric living creatures. Now with genomics and proteomics, we can reach ten times further back in time compared to before," said Professor Eske Willerslev, who also led the study. "And new knowledge about the horse's evolutionary history has been added - a history which is considered as a classical example in evolutionary biology and a topic which is taught in high schools and universities."
