Re: DISCOVER/Neanderthal/Homo Sap.

JamShreeve (jamshreeve@aol.com)
6 Sep 1995 07:56:51 -0400

It is nice to see that the excerpt of my book in Discover has inspired
such an intense discussion. A couple of quick responses of my own:

There is no consensus over whether modern humans and Neandertals
interbred. Those who think they did, such as Wolpoff and many of his
students, do refer to some fossils in eastern Europe as transitional,
including skulls from Mladec and Vindija. But these skulls are not their
only support. More important are features of Neandertal anatomy that may
also appear in modern Europeans with greater frequency than they appear in
other living modern humans. Projecting noses, for instance, or a rounded
lump on the back of the skull called an occipital bun. Those who think
that the Neandertals were a separate species, for instance Ian Tattersall
and Chris Stringer, point to the complete absence of any transitional
fossils where the most Neandertals are found - western Europe and the
Middle East. As the article in Discover points out, the argument I find
most convincing is the lack of any blending in the Middle East through
time. But it is hardly the final word.

The analogy with diverse dog breeds that can all reproduce is a little
strange. It doesn't really matter that there is so much morphological
difference between a Beagle and a Greyhound, because their "mate
recognition system" is not based on visual stimulation to begin with. As
far as I know, and I'm not a dog myself, the primary sexual cues in
canines are based on scent. So if you want to bring this analogy to bear
on the Neandertal-modern human question more accurately, consider a
hypothetical population of generic dogs who become isolated from each
other. They both start out with the same morphology and natural selection
works vastly slower than artificial selection, so after 20,000 years,
let's say they look pretty much the same. But for whatever reason - let's
say genetic drift - they no longer give off the same olfactory cues. When
they get together again, the scent of a female from one population just
doesn't shout "mate!" to the male of the other. They have become
reprodutively isolated, no matter how much they look like each other.

Now, human mating cues do have an extremely important visual component,
and we are particularly sensitive and drawn to the face. Since the face
is the anatomical region where you see the most difference between
Neandertals and modern humans, I suggest that perhaps they might have not
recognized each other as potential mates. Obviously that is speculation,
and several people on this thread have argued that the differences aren't
all that great. True, perhaps - but don't forget, we don't have the soft
anatomy that in life might have amplified and refined those differences.
There are species of guenons (forest monkeys) in central Africa which are
virtually indistinguishable on the basis of their skeletons. They live in
the same areas, and some may even forage together for days or weeks on
end. But they do not interbreed. Their mate recognition systems are also
highly visual. The different species have very distinct markings and
bands of color - on the face.

There is a great deal more to all this, and I wish I could address some
more of the points being made here, but I'm supposed to be working.
Without wanting to sound like I'm just hawking my own book, this is all
explored there in greater depth. It's called The Neandertal Enigma and
should be around in stores soon. Other excellent new books are Ian
Tattersall's The Fossil Trail, and The Neandertals, by Erik Trinkaus and
Pat Shipman.

James Shreeve