In a new study published in the journal eLife, scientists apply big-data analysis to reveal the full extent of viruses’ impact on the evolution of humans and other mammals. Their findings suggest 30% of all protein adaptations since humans’ divergence with chimpanzees have been driven by viruses.
When an environmental change occurs, species are able to adapt in response due to mutations in their DNA. Although these mutations occur randomly, by chance some of them make the organism better suited to their new environment. These are known as adaptive mutations.
In the past decade, scientists have discovered a large number of adaptive mutations in a wide variety of locations in the genome of humans and other mammals.
The fact that adaptive mutations are so pervasive is puzzling. What kind of environmental pressure could possibly drive so much adaptation in so many parts of the genome?
Viruses are ideal suspects since they are always present, ever-changing and interact with hundreds to thousands of proteins.
“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 lead author Dr. David Enard, of Stanford University.
“We knew that, but what really surprised us is the strength and clarity of the pattern we found.”
(...) “The discovery that this constant battle with viruses has shaped us in every aspect — not just the few proteins that fight infections, but everything — is profound.”
“All organisms have been living with viruses for billions of years; this work shows that those interactions have affected every part of the cell.”
Viruses hijack nearly every function of a host organism’s cells in order to replicate and spread, so it makes sense that they would drive the evolution of the cellular machinery to a greater extent than other evolutionary pressures such as predation or environmental conditions.