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Re: puzzle of the negrito: isolated archaic populations
Philip Deitiker (pdeitik@bcm.tmc.edu)
Mon, 16 Dec 1996 22:53:50 GMT
larryc@teleport.com (Larry Caldwell) wrote:
>In article <E2BCAq.8FM@liverpool.ac.uk>, dbarnes@liv.ac.uk (Dan Barnes) wrote:
>> In article <584qot$p0j@news.sdd.hp.com>, geroldf@sdd.hp.com says...
>> >andaman islands, and possibly india as well. Average height for men
>> >ranged from around 4 1/2 feet to just under 5, leading to the name
>> need. From these results it is not suprising that a people who have spent a long
>> time living exclusively in rain forests would develop a decrease in height. It
>> would seem that if Ruff's analysis is valid that it is an example of parallel
>> evolution - with two groups of people adapting to similar environmental
>This whole discussion is based on the proposition that height is determined
>by genetics. This is not true. The average caucasian height was 5'4" only
>a century ago, and has varied up and down with diet for centuries. It
>takes at least two generations of changed diet to express fully, probably
>because of maternal influences.
>Put them on a beefsteak and bean diet for two generations and then measure
>their height. Until then, you have no data whatever.
Actually (in addition to what was said) start exposing them to milk
products and beign to develop selective lactose tolerance) then
increase the amount of milk products (as well as having doses of FDA
approved vitamin D) in the diet. This could take more than two
generations. This will probably add a couple of inches. In addtion
a\eliminate all debilitating childhood diseases, and a whole host of
factros which interfere with _OPTIMAL_ growth.
In gerald's defense I must add that there are groups of peoples who
are, despite their diets, shorter in stature. This does probably
relate to regional selection. But let's make the comparison of human
size and shape with a common regionally (albeit artificially) selected
animal (the household canine) and the relataive range of human size
and shape should be considered minimal. The point is that alterations
in size and shape do not make a species. There is another issue which
gets waxed over in these arguments is that skeleta does not = form. To
the bones are added cartilage, muscle, hair color, skin textures,
color patterns, etc. While the bone structure of asian erectus may
have been similar to sapiens, no qualifications can be made whether
this animal might be recognized as human by humans at that time.
The question might be germane is that after 300 KYA of separation
between toy poodle and great dane would (could) such a cross produce
viable offspring.
Then, the real question is be looked for. The canine example above
does not take into account a very important parameter, time. As time
progresses genetic and chromosomal drift between isolated populations
may result in a partition to interbreeding. Domestic dogs have been
worked on for about 12,000 years whereas we have no instance for
out-of-africa-derived H.S. outbreeding for 200,000 years. Supposedly
there are now two instances were the possibility could have occured
but if so interbreed is not evident in the results. A second phenomena
is the presence of neaderthals separating asian erectus and african
erectus>sapiens, and presents a scenario that neaderthals may have
inhibited (or created isolation barrier) for more >400,000 years. Not
to mention that neaderthalensis and sapiens are more similar than
sapiens and erectus (still with no evidence of crossing). I have
created some controversy before but I think the best explanation that
comes from the current set of data is that erectus>sapiens line which
developed in africa began to fully partition from the extra-subsaharan
african population sometime between 1M and 400KYA and may have been
subpartitioned with the SSA region before 150 KYA. The reason I say
this is that the genetic data really only points to when the last
major bottleneck event occured in the extant lineage, the bottleneck
may have existed for a time but was obscured by the population size
(resticting the interval between the present and the exidous from the
bottleneck).
To add to this the current data suggests that the subsaharan african
population did not expand very rapidly, suggesting that this
population was contained in size by reasonably competitive adjacent
homind forms for a long period of time. Secondarily there are these
two other hominids which at 100 KYA neaderthal and humans don't
interbreed yet current humans which are related by >120KY apparently
can. Thus, in all likelyhood we are looking at typical species
divergence times in genus homo of probably > 300KY. Thus if the
assumption is made that african is the cradle of modern human
evolution for > 400KY then events in eurasia are demonstrative of
regional evolution which occured in those areas with varying degrees
of intertype interbreeding which faded overtime.
I wouldn't be at all surprised if, in the future, the fossile
record demostrates that several likely species/ regional varients
existed over the last 400 KY, with each more progressed (toward
sapiens) form of homo radiates from its african core and this flux
results in the rearrangement (displacement) of hominids both in and
out of africa, eventually resulting in extra-african populations vying
for territories by regional selection, alas the final form comes forth
and in turn wipes all these out. If the modern period had not
developed this process might have continued still, and, if so, it begs
the question about what so special about africa that it
it seems to be producing all these more-competitive lineages? Does
this have something to do with the great variation of animals which
live in africa, or because of climate and humans long existance there
that this region has/was conditioned as a site for optimal hominid
evolution. Even if one looks at socialization patterns, the birthplace
of modern human civilization seems to be rooted in africa (although
SSA association is debatable), even though there seems to be areas
much more suitable for its development (indus valley, northwestern
medditeranean).
Philip
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