A study shows how extensively viruses from as far back as the dinosaur era still thrive in our genetic material.
The scientists investigated the genomes of 38 mammals including humans, mice, rats, elephants and dolphins.
One of the viruses was found to have invaded the genome of a common ancestor around 100 million years ago with its remnants discovered in almost every mammal in the study.
Another infected an early primate with the result that it was found in apes, humans and other primates as well.
The work established that many of these viruses lost the ability to transfer from one cell to another.
Instead they evolved to stay within their host cell where they have profilerated very effectively — spending their entire life cycle within the cell.
There are other reports of similar finding. For example:
8 Percent of Human Genome Was Inserted By Virus, and May Cause Schizophrenia
Bornaviruses, a type of RNA virus that causes disease in horses and sheep, first inserted their genetic material into ancestral human DNA at least 40 million years ago