The Origin, and the Sickening, of Our Species: “If one of your hominoid ancestors hadn’t gotten a viral infection millions of years ago, you might look really, really different today.

In the beginning, before the first landlubbers crawled out of the murky ocean depths, viruses were everywhere. These parasites infected our earliest ancestors, and today, many millions of years later, bits of their genes live on in our genes.

For three decades, scientists have wondered whether the viral DNA within us is more than merely a vestige of our lowly origins. Could these infectious organisms have assisted in driving our evolution-by helping, say, to turn a foraging ape into a more cerebral toolmaker?” Popular Science