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Re: Origins of human thought - needinfo
Philip Deitiker (Pdeitik@bcm.tmc.edu)
11 Oct 1995 18:35:24 GMT
Probably the most pertenant information concerning this topic (that I
hold any faith in) are the human genetics studies of folks that lack
various abilities (specific) in their language and related logic
pathways. A number of papers have been written recently on the topic,
some in common journals. A literature search using language, human,
genetics as search terms should be the best way to determine these.
As far as timing is concerned this is more difficult and I really don't
know to what degree homologues are present in the great apes (the
literature in this area may be illuminating.).
There are two broad issues concering these characteristics as I see it.
The evolution of the infrastructure.
As the human brain expanded specific regions on the left (regions 42 &
43) expanded more than others. These regions are the last regions of the
brain to develope during ontology, and developement is concurrent with
the aquisition of language and complex thought. Trauma to these areas
frequently results in language loss. To the degree that skulls have been
found these skulls predict the infrastructure has been present for much
greator than 50 kY, genetic evidence (divergence times of both
mitochondria and the y chromosome) suggest 150-250 kY.
The individual processes involved.
The human genetic studies indicate a number of logic/language pathways.
Within this issue is the fact that the subsystem is somewhat redundant
and affected indiviuals have compensatory mechanisms for some of the
traits. A question one could ask is are the language/logic regions
diminished (in size) in individuals which have defect, I really don't
know. Without this information the arguments of the timing of origns of
some of these pathways is at issue. Apriori I would use the 150-250 kY
date, but the language experts that I know are dubious.
I would support older date because it seems likely that brain size and
these important pathways evolved simulataneously with the evolution of
langauge, because of the mitochondrial and y chomosome dates and the
isolation of human populations occured prior to 50 kYA. This means that
for the hypothesis not to be true that all such pathways would have had
to develope and thoroughly spread completely through a preexisting
population spread over africa, europe and asia OR that the pathways
coevolved in/or were selected for in those isolated populations,
(predicting selective pressures changed simulataneously throughout the
world).
Having said this I must make the point that the period from 35-150 kYA
is not a fantastically enlightening period of human developement. Tool
mechanics improved very little (although soft artifacts may be absent
from the archeological record), although there is some evidence to
suggest that tools were being used to procure a greator variety of foods,
and to develop other aspects of paleolithic life. There is little
indication that humans interacted in more complex ways prior to the last
ice-age. The fact that humans began (both in asia and the americas) this
drive for more complex societies _may_ be indicative of a very last wave
of human intelligence gene(s), and that previous waves of intelligence
improvents were sub-threshold levels.
One could counter this arguments and all arguments for recent
evolutionary events by proving that technological evolution even in
potential geniouses required the advancement of complex 'threshold'
technologigies such as writing, transportation, building, ect. And that
the evolution of civilization was held back not by brain power but by the
convergence of technological advancements and core understandings of
moral phenomena. Prior to this period, prove that we had logic but it was
being used to open clams, make fires and dig grubs out of the ground,
and that we had language but it was used to take about very simple
things.
The relationship between genetic advancement and human intelligence is
a very difficult issue to resolve. If I were undertaking this I would
really begin my search comparing human language genes with their
homologues in both chimps, gorillas, and other greater apes. This may
give some idea about possible duplication events and divergence times
(presuming that mutations did occur), both intronic, flanking and exonic
since the protein sequences may not be causative difference. In addition
popluation mol. genetic studies (like the ones done for mitochondria and
the y chromosome) can set a baseline of acceptable variations within
these genes. You may not have to do as thorough a study as the mit and Y
people, because they have already documented the most genetically
peripheral groups of humans and thus a fewer human samples need to be
compared.
Philip
Philip
Philip
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