Link: Evolutionary rate of viruses within our genomes

Carl Zimmer has a nice post today discussing the evolution of endogenous retroviruses in primates: “Our Inner Viruses: Forty Million Years In the Making”. Fragments of viruses make up more than five percent of our genome. Most of them are legacies of ancient primate evolution, but a few have been active during the last few million years. Zimmer describes a new study by Gkikas Magiorkinis and colleagues that estimates the times of activity of the major ERV types:

In the Old World monkeys–represented in the new study by baboons and macaques–the rate of new virus copies pretty much stayed the same over the past 30 million years. But the apes tell a different story. The rate dropped in every ape branch. The same shift occurred in parallel in the ancestors of humans, chimpanzees, gorillas, orangutans, and gibbons.

Zimmer discusses some reasons that may explain this slowdown, including larger body size and reduced transmission between individuals, but with no clear answers.