By analyzing and comparing genetic data from different species, a research team led by University of California, Santa Cruz (UCSC) scientists estimated that certain endogenous retroviruses (ERVs) entered the genome about 40 million years ago, and spread rapidly in primates about 25 million years ago.

The study offers an explanation for how regulatory networks of genes evolved and provided a mechanism to quickly establish a gene regulatory network (based on the p53 gene) in a very short evolutionary time frame.

These results raise new questions about the role of so-called “junk DNA,” the vast regions of the genome that don’t code for proteins. ERVs fall into that category. Many scientists once believed that such DNA served no purpose, but new data from the UCSC lab and other labs are challenging that view.