Head lice have been constant, if unwanted, human companions. The blood-sucking parasites are rich sources of genetic information illuminating some of the biggest questions in the human story.

Head lice have been constant, if unwanted, human companions for as long as our species has been around. Evidence of this ancient connection includes a 10,000-year-old louse found on human remains at ...

In fact, head lice have been clinging to human hair for as long as there've been humans — and likely even before that to the hair of our hominid ancestors.

In fact, head lice have been clinging to human hair for as long as there've been humans — and likely even before that to the hair of our hominid ancestors.

Humans and lice have coevolved for thousands of years. The oldest human louse known to scientists is a 10,000 year-old specimen from Brazil. Getty Images ...

Head lice, scientifically known as Pediculus humanus capitis, are tiny parasitic insects that feed on blood from the human scalp; they most frequently affect kids.

Head lice have been constant, if unwanted, human companions for as long as our species has been around. Evidence of this ancient connection includes a 10,000-year-old louse found on human remains ...

Head lice are considered a nuisance — a pest to be evicted from the hair on your head or the head of a loved one with a special comb or shampoo. But there's more to lice than their elimination ...

Lice have irked humans for many centuries. In this 1497 woodcut printed in Strasburg, Germany, a man is de-loused. (Science & Society Picture Library via Getty Images) Head lice are considered a ...