Viruses may have played a significant role in human evolution, rather than just giving us infections and diseases, a new study has found.
The constant battle between pathogens and their hosts has long been recognised as a key driver of evolution, but until now scientists have not had the tools to look at these patterns globally across species and genomes.
In a new study, researchers apply big-data analysis to reveal the full extent of viruses' impact on the evolution of humans and other mammals.
The findings suggest an astonishing 30 per cent of all protein adaptations since humans' divergence with chimpanzees have been driven by viruses.
"When you have a pandemic or an epidemic at some point in evolution, the population that is targeted by the virus either adapts, or goes extinct," said David Enard, a postdoctoral fellow at Stanford University.
"We knew that, but what really surprised us is the strength and clarity of the pattern we found," said Enard.
"This is the first time that viruses have been shown to have such a strong impact on adaptation," he said.
Proteins perform a vast array of functions that keep our cells ticking. By unveiling how small tweaks in protein shape and composition have helped humans and other mammals respond to viruses, the study could help researchers find new therapeutic leads against today's viral threats.
"We're learning which parts of the cell have been used to fight viruses in the past, presumably without detrimental effects on the organism," said Dmitri Petrov, professor at Stanford.
Previous research on the interactions between viruses and proteins has focused almost exclusively on individual proteins that are directly involved in the immune response - the most logical place you would expect to find adaptations driven by viruses.
This is the first study to take a global look at all types of proteins.
"It's not only very specialised immune proteins that adapt against viruses. Any type of protein that comes into contact with viruses can participate in the adaptation against viruses," said Enard.
"It turns out that there is at least as much adaptation outside of the immune response as within it," he added.
The team's first step was to identify all the proteins that are known to physically interact with viruses.
After reviewing tens of thousands of scientific abstracts, Enard culled the list to about 1,300 proteins of interest.
He then built big-data algorithms to scour genomic databases and compare the evolution of virus-interacting proteins to that of other proteins.
The results showed that adaptations have occurred three times as frequently in virus-interacting proteins compared with other proteins.
The study was published in the journal eLife.
