News: Gorillas Gave Pubic Lice to Humans

Gorillas Gave Pubic Lice to Humans, DNA Study Reveals
http://news.nationalgeographic.com/news/2007/03/070316-gorilla-lice.html?source=rss

Scott Norris for National Geographic News
March 16, 2007

What exactly went on between gorillas and early humans? No one knows
for sure, but scientists say one thing, at least, seems certain: The
big apes gave us pubic lice.

Researchers made the uncomfortable discovery during a DNA study
reconstructing the evolutionary history of lice in humans and our
primate relatives.

The transfer occurred about 3.3 million years ago, said study leader
David Reed, of the University of Florida in Gainesville. That's when
the gorilla louse and the human pubic louse separated into distinct
species, the research revealed.

Modern humans (Homo sapiens) weren't around at the time. So the first
to be infested by the new lice species were probably Australopithecus,
a group of human ancestors that include the famous "Lucy" fossil.

Prior to the transfer our ancestors were troubled by only one species
of body louse, as chimpanzees and gorillas are today. Why humans can
harbor two species?head lice and pubic lice?has been a mystery until
now.

The discovery raises the same vexing question faced by anyone who has
contracted pubic lice: How exactly did this happen?

Pubic lice are spread most commonly through sexual contact, but that's
not necessarily how our ancestors acquired the parasite from gorillas.

"Unfortunately, we'll never know for sure," Reed said. "Given that the
[gorilla louse] species occurs primarily in the pubic region, it is
quite possible that the lice were transmitted sexually."

A more likely scenario, though, is that early humans picked up the
parasites simply by living in close proximity to gorillas, perhaps
using the animals' sleeping sites or scavenging gorilla remains, he
said.

The study appears in a recent edition of the journal BMC Biology.

Good Night, Gorilla

Reed's team studied changes in primate and lice genes to determine
when different louse species originated.

Human head lice share a common ancestor with chimpanzee lice. The new
data showed that the two emerged as separate species at the same time
that humans and chimps parted evolutionary ways, about six million
years ago.

Such co-speciation is typical of lice and other parasites, which can
often evolve in tandem with their animal hosts.

Our pubic lice, by contrast, are most closely related to the gorilla
louse. But gorilla and human lineages diverged seven million years
ago, so co-speciation couldn't explain the origin of the pubic louse.

Instead, the parasite must have spread from one primate to the other
long after they had evolved into separate species.

Even discounting the possibility of sexual transmission, the discovery
gives anthropologists intriguing new information about the lifestyle
and behavior of early human ancestors.

"These results may suggest that [our ancestors] lived or partially
dwelt in forests and perhaps even slept in nests of foliage built by
gorillas," said Mark Pagel, of the University of Reading in England.

Our Bodies, Our Habitats

Understanding where human lice came from still doesn't fully explain
our unusual capacity to harbor two distinct varieties of the
bloodsucking parasite.

For lice, each host species is, in effect, a unique "island" of
habitat, study leader Reed noted. The parasites become adapted to
local conditions such as hair size and blood type.

"[Lice] are simply stranded on their hosts with no means of escape,"
he explained. "They can't fly, they can't jump, and they can't live
apart from the host for any period of time."

The loss of hair over most of our bodies may have created two distinct
habitat islands in humans. The scalp and pubic regions differ
significantly?and they are separated by largely inhospitable terrain.

"Pubic lice could not have established on humans without suitable
habitat," Reed said. "Loss of body hair would have left the pubic
region an open island of habitat that [the gorilla louse] could have
colonized."

Dale Clayton, of the University of Utah in Salt Lake City, called it
"a fascinating example of ecological opportunism."

"Different hair diameters [in the scalp and pubic regions] probably
represent different habitat templates," he said, "just as
different-size tree branches are used by different species of birds."

--
Bob.

.

Relevant Pages

  • Re: News: Gorillas Gave Pubic Lice to Humans
    ... What exactly went on between gorillas and early humans? ... the gorilla louse and the human pubic louse separated into distinct ... Prior to the transfer our ancestors were troubled by only one species ...
    (talk.origins)
  • Lucy = fossil Gorilla species?
    ... 'Lucy' is not direct ancestor of humans ... branch of the great apes family known as the "Robust hominids." ... Gorilla-like anatomy on Australopithecus afarensis mandibles suggests ... A.L.333 specimens "looked very much like a small female gorilla." ...
    (sci.anthropology.paleo)
  • Re: Link To Full Paper Re: Lice Evolution May Reflect sapiens/erectus Contact
    ... That's certainly the case for lice. ... we humans are the world. ... spread out of their birthplace in Africa to other parts of the world. ... The fossils of Homo erectus from a few hundred thousand years ago look ...
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  • Re: Lucy = fossil relative of Gorilla rather than of Homo or Pan?
    ... A.L.333 specimens "looked very much like a small female gorilla." ... the extant apes among other hominoids... ... there's nothing Homo-like in afarensis: ... afarensis is related to gorillas rather than to humans. ...
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  • Re: We are apes.
    ... "apes morphed into men." ... fallacy (though not for the reason most creationists would suppose). ... The reason it is a fallacy is that humans are, and always have been, ... Western Gorilla, Gorilla gorilla ...
    (talk.origins)
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