Was Silverback Mountain to Blame for Lice in Your Nest?

ResearchBlogging.orgThere are two species of lice that infest humans: pubic lice, Pthirus pubis, and human head and body lice, Pediculus humanus.

Weiss points out that our evolutionary ancestors were uniformly hairy so why did two types of lice emerge.

“I was having difficulty envisioning a clear separation of habitats between the groin and other parts of our ancient common ancestor,” explains Weiss, “My eureka moment came, appropriately enough, in the shower: although naked apes have pubic hair, surely our hairy cousins don’t?”

In other words, as “naked” apes, we’re the only members of the family group with pubes!

Pthirus pubis, popularly known as crabs, evolved from the structurally similar gorilla louse, Pthirus gorillae.

Genetic analysis by David Reed of the University of Florida suggests that the lousy split happened 3.3 million years ago. But, humans diverged from a common ape-like ancestor much earlier; at least 7 million years ago. This suggests that early humans somehow caught pubic lice from their gorilla cousins, as Sciencebase reported previously.

Of course, this is not about some kind of romantic gorillas in the mist, silverback mountain moment in human history or about our hairy cousins inviting us back to their nests. Although that said, in the jungle a man’s gotta do what a gorilla’s gotta tell ‘im

No, according to Weiss, “Before one conjures up a mini King Kong scenario, it should be noted that predators can pick up parasites from their prey. The close contact involved in human ancestors butchering gorillas could have enabled Pthirus to jump hosts, rather as bushmeat slaughter practices allowed HIV to invade humans from chimpanzees in modern times.”

So, while head lice may be viewed as a `family heirloom’, inherited down the generations as humans have evolved, pubic lice may well be a recent and slightly unwelcome gift from the more hirsute branch of our evolutionary family.

The research is published in the BMC Journal of Biology

Robin A Weiss (2009). Apes, lice and prehistory Journal of Biology, 8 (2) DOI: 10.1186/jbiol114