Why didn’t we hatch from eggs? Thank viruses, says biologist

Whether you know it or not, you’ve already gone viral — hundreds of thousands of times, in fact. Viruses are part of who we are in a very concrete way. Fully 8 percent of our genetic code comes not from human ancestors, but from viruses, according to Harmit Malik. “Things we consider bonafide human genes and human biological processes actually owe their roots to something that came from a virus,” says Malik, a faculty member at the Fred Hutchinson Cancer Research Center. Malik is especially interested in a type of virus called a retrovirus — the virus that causes HIV is a famous one. A retrovirus enters a host cell, copies its own genetic material, and inserts that copy into the host’s DNA. If that host cell happens to form a sperm or egg, the viral-origin DNA gets passed on to the next generations. Multiply that a few hundred thousand times (at least — Malik...