No subject


Sun Apr 10 21:17:45 EST 2005


        The developing trend in both natural and social sciences
continues to be towards long-term collaboration between formerly
disparate disciplines. Inevitably this meets with difficulties due
to differences in terminologies used in the separate groupings,
nevertheless the close contact develops cross-fertilisation that
erodes and breaks through these barriers.
        That this is happening in neuroscience must be abundantly
clear to most who read these lines, especially those who watch some
of the "flaming" episodes on some of the Internet news groups, but
these are sooner or later settled with deeper understanding of the
processes involved. But they can never, by the very nature of all
science, be smooth uninterrupted paths of development.  

        A recent book, "The Neandertal Enigma", by James Greeve,
shows that similar things are happening in Palaeoanthropology,
which incidentally appears to be connected with the course of
development in neuroscience. The basis for this particular link
concerns a genetic "punctuation", a term introduced by Eldridge &
Gould, but now redefined more precisely, that appears to have
been taking place among our ancestors as recently as 140,000 years
ago, most probably first in Africa. As it affected brain chemistry,
clearly it cannot appear in our ancestors bones, but does
indirectly appear in their cultural objects.
        Greeve is a science journalist who spent several years
tracking down what is known about human origins and the very human
and not always very "scientific" struggles that have been and still
are involved in the tracing thereof. He opens by recounting his own
first encounter in a Paris cafe with a Neandertal jaw bone and
learning about its differences from modern humans of all living
races. There he also learned of the debate that still rages between
palaeontologists about their relationship to ourselves - can we
count them among our direct ancestors or were they like aunts and
uncles dying without issue only indirect relations?
        It was not until Crick & Watson  announced the Double Helix
of DNA that we had any way of tracing ancestry to any reliable
degree of certainty. Morphology can give pointers but no more than
that. Blood typing places us close to chimpanzees which pleased
originators of the "African Eve" idea, but morphology speaks
otherwise. The use of mitochondrial DNA by many of the scientists
Greeve interviewed is impressive. It was telling them that the *most
recent* common ancestor in the *direct all-female line* was one of
the African Bush People but nothing about the lines of descent that
include both sexes, which is by far the greatest part of our
ancestry. Moreover, that particular woman had 2 parents so in the
end the direct female line becomes irrelevant to further research,
as is logically inevitable, even if on very rare occasions spermal
mitochondria do enter the ovum. 
        However, this does not mean the mitochondrial DNA line of
research into human origins was a waste of time. It does tell us
"Eve" was a member of a population that was among the most rapidly
increasing at the time she died, a population that was *most likely
to spread* into other areas. The question Greeve faced is - What gave
her people this advantage? He went to the land of the African Bush-
People to find out.

        He found Kathy Brooks working at Kashanga where there was
an assortment of finely-worked tools most probably harpoon heads.
These were finally dated significantly much earlier than any known
Cromagnon tools and Upper Palaeolithic tools generally. They
showed nevertheless imaginative skills not found in Early and
Middle Stone Age collections. Then Temple and Madisson revised and
improved on the computer program that had started the mad
chase after the "African Eve". They showed that re-runs of the
mew program could put "Eve" randomly in any inhabitable part of the
Earth. But what stood firm was the evidence of a rapid development
of *imagination* in the production of artifacts beginning about the
same time as she lived. This points to some heritable change in
brain chemistry that affected our consciousness of the world..

        By introducing this concept we are introduced to study of
how new ideas, new perceptions, are born, as well as how they spread
through populations.

        Invention is either a form of dreaming or very closely
related to it, and like hallucination, entails some degree
of detachment from the immediate reality of which we are
conscious. This is apparent in  the classic stories of Archimedes,
both in the Eureka! experience and in the story of his death at the
hands of a Roman soldier. Koehler's apes who improvised means of
reaching fruit that was out of reach showed momentarily this same
detachment before taking action.
        In all such cases natural narcotics and hallucinogens
produced in our brains are involved. Some of them we share with
other animals, In the course of a fight the experience of pain
could be a distraction resulting in death, hence pain centres are
selectively switched off, but afterwards, when the immediate danger
has passed and there is danger of infection in wounds, pain
perception is switched on to trigger wound-licking. All these
chemical switching processes are products of rare favourable
mutations, a phenomenon first postulated under the title of
punctuation by Eldredge & Gould. A recent series of experiments
with a selected strain of the gut bacterium Eschericia coli (Elena,
Cooper and Lenski,Science 272, pp 1802-1804, 1996) has shown that
the phenomenon exists under steady-state conditions in a deprived
environment.
        The glaciations of the pleistocene represent on a global
scale the deprived type of environment in which punctuated evolution
occurs. Enhancement of imagination by further enrichment of the
hominid brain's chemical system of conscious image formation -
dreaming, has been  the most spectacular of these adaptations.

Gordon Gray




More information about the Neur-sci mailing list