Re: DISCOVER/Neanderthal/Homo Sap.
Gerrit Hanenburg (ghanenbu@inter.nl.net)
Mon, 4 Sep 1995 16:07:34 GMT
hubey@pegasus.montclair.edu (H. M. Hubey) wrote:
Your previous reply was somewhat meager.Thanks for the additional comment.
Now I get the point.
Your example illustrates:
If all the different breeds of Canis familiaris were only known from
fossils,most of them would have been assigned to a different species or even
a different genus.And we would have been plain wrong.
So,how can I assess that Neanderthals are a different species,reproductively
isolated from modern humans,just on the basis of some (in your opinion) minor
anatomical differences?
>The fact is that the hotdog dachshund is a dog, just like the
>sleek and large Afghan hound. A bulldog is a dog, just like the
>Kangal. etc. Now explain why the "theory" that the Neanderthals
>and the Cro-magnons were a different species because of some
>bumps on the skull or some other small change in skull shapes
>doesn't operate with dogs.
According to the biological species concept all dogs belong to same species.
This is by definition because they are still able to interbreed (in
principle,although I doubt a Chihuahua and Great Dane can actually be crossed
without in vitro fertilization techniques).However the biological species
concept is not applicable to the fossil record.What we have here is,I think,a
confusion of biological species and palaeontological species.A
palaeontological species is established on the basis of morphology and
stratigraphy and doesn't necessarily coincide with a biological species (that
would have been wonderful).It may well be that a palaeontological species is
just a morphological cluster of individuals deemed useful to establish.It may
also have been a biological species but that status is hypothetical.Can we
gain any confidence as to the status of a palaeontological species like the
Neanderthal.I think we can,by comparing the differences between Neanderthals
and modern humans with those between other "wildtype" species.We shouldn't
compare them with the domestic dog but with a natural species cluster such as
that of the Cape fox,red fox,fennec fox,kit fox and Artic fox (all full
species) because we may assume that these species have been subject to the
same proces of natural selection as Neanderthals and early modern humans.
(even better of course is to compare them with other primate groups)
>What makes artificial selection different. Does it work against
>the laws of genetics? Or does it merely speed things up in
>a specific direction according to the selector?
Domestication is an evolutionary process.It doesn't violate any genetic
laws.The different breeds of dogs can be considered an adaptive radiation
into a new ecological niche (domestic association with humans) which has led
to major morphological differences but no reproductive isolation
(yet),possibly because of the recency of the process.
An important difference however between artificial and natural selection is
intentionality.Natural selection has no intentions,no goal and doesn't plan
ahead.Artificial selection in its most advanced forms is more like designing.
The speeding up of the process may also be of great importance for it may be
this that leads to uncoupling of morphological change and speciation (i.e.the
establishment of reproductive isolation).It's conceivable that morphology is
more subject to change under artificial selection while the processes that
may lead to reproductive isolation are less so.(they may have a more random
character. e.g.in one instance only one major event like a chromosomal
inversion may be enough for genetic incompatibility while in another case the
cumulation of several genetic events is required.Artificial selection may not
have any influence on this).
Gerrit.
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