Sympatric Gorillas and Chimpanzees, a Question of Lice and a Clue to the Origin of Homo Sapiens

Sympatric is a "new" word for many. Google define results in:

"sym·pat·ric  

/simˈpatrik/

Adjective

1. (of animals or plants, esp. of related species or populations) Occurring within the same geographical area; overlapping in distribution.
2. (of speciation) Taking place without geographical separation."

So what does "sympatric" have to do with lice and the origin of species?

One of the remarkable things about science is that answers to troublesome questions often are found in the unlikeliest places.

Lice provide a good example of an unexpected clue to homo sapiens (i.e. mankind as a species).

As noted at the University of Florida News in
Human pubic lice acquired from gorillas gives evolutionary clues
discussing the research of "David Reed, assistant curator of mammals at the Florida Museum of Natural History":

"Reed and his co-workers’ research stemmed from their fascination with humans' unique position among primates in being host to two different kinds of lice: one on the head and body (Pediculus), which has become the bane of many schoolchildren, and pubic or crab lice (Pthirus). In contrast, chimps have only head lice and gorillas pubic lice." (emphasis and italics added) 

The question of why chimpanzees have only Pediculus and gorillas have only Pthirus, while humans can be infested with both types of lice, has puzzled the genetic community.

As written by Scott Norris at National Geographic news in
Gorillas Gave Pubic Lice to Humans, DNA Study Reveals:

"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."

But what about head and body lice and their infestation of chimpanzees?

Why and how did humans get and keep BOTH lice types, whereas each appears to be a specialized form originally adapted to either gorilla or chimp but not both?

The John Hawks weblog has discussion of possible solutions at
Three million years of unwanted guests. None of them fits exactly.

One solution, not considered there, is found at LexiLine. Take a look.

Gorillas and Chimpanzees are "sympatric" in only one region of Africa, and that is precisely the region in which Australopithecus has been found.

Perhaps a hybridization of gorilla and chimp might be the answer.