One of the greatest mysteries in biology is how new species come into
existence. This was a question that Darwin struggled with over his lifetime
-- and thousands of other biologists ever since. Selection of the fittest,
further quality controlled by sexual selection of males by females
certainly accounts for evolution within a species but not for the sudden
appearances of startlingly new species that are found in the fossil record.
Recent research by scientists at the Genome Institute of Singapore and the
Graduate medical School of Princeton University among others have
conclusively shown that viruses have played a huge part in the way genes
are regulated for millions of years. The same evidence is also highly
suggestive -- but not yet fully proven -- that viruses are the cause of new
species.
Back in the 1950s, Nobel laureate Barbara McClintock proposed that residual
RNA sequences (virus equivalents of our DNA), left over from unsuccessful
viral attacks, were incorporated into our genes in the form of highly
mobile units which dashed around our more sedate "normal" genes, regulating
their starts and stops. The latest research, published in Nature Genetics
last week, now proves that this is so.
The development of the embryo in the womb is rather like a huge orchestra
(of our "standard" genes) being gradually worked up into full symphonic
performance by a succession of conductors following each other on the
rostrum. The first embryonic stem cell -- the result of the male sperm and
the female egg joining together -- is taken through stage after stage of
development by regulatory proteins, themselves the products of virus RNA
working backwards into our human DNA.
One of the immediate benefits of the new finding is that it may now be
possible to start thinking of treating degenerative diseases such as
Parkinson's, leukemia and the like. In these case the regulatory proteins
have started to go awry, causing genes to express themselves out of their
correct order. By implanting brand new stem cells into affected regions of
the brain and elsewhere, and then re-setting their genes precisely to the
stage when they produce healthy cellular offspring again, then the faulty
cells can be crowded out, as it were, and die in the usual way.
At about the same time as Barbara McClintock was proposing regulators as
remnants of virus attacks, another brilliant biologist, Lynn Margulis, was
proposing that some viruses actually incorporate themselves into our DNA as
full-blown new genes and thereby cause a new species to come into
existence. This was rejected out of hand by most biologists, but no longer.
In the last few years, research by D. G. Knowles and A. McLysaght at Dublin
University proves that human beings have at least ten brand new genes --
and probably as many as twenty -- that have DNA sequences quite unlike any
that existed before, of which both we and the chimpanzee have similar
versions. It is conjectured that these new genes are the result of
virological attacks which we smothered and immobilized rather than fell
victim to.
Darwin never claimed to know how new species arise but he assumed -- as
thousands of biologists since -- that one species gradually drifted apart
from another one by means of an accumulation of genetic variations. Genetic
drifting within a species -- especially if it's stretched out over a large
geographical area -- does indeed take place. There are hundreds of current
examples in living species, but it still doesn't explain why there are no
fossils of intermediate species. A new species always arrives suddenly.
Besides, if slow origination of species occurs then brother-sister sexual
partnerships must be implicated because the last variation could only
arrive in one person originally. But such a sexual partnership is something
that simply never happens -- either in our species or in any other primate
-- except in very rare circumstances where a brother and sister are
separated very early in childhood and accidentally, and unknowingly,
re-discover each other.
On the other hand, if a virus attacks a whole human population -- perhaps
killing some -- then many of the survivors might be incorporating the
remnants of the new virus in their DNA. Strictly speaking this can only
happen in a pre-pubescent boy while his sperm-producing cells are
developing and preparing a template DNA. But if thousands or tens of
thousands of young men with an additional new gene finally marry they might
produce offspring, male and female, with a quite new visible change as a
byproduct. If the "quirky" new females preferably choose those males with
the same new appearance (a larger forehead perhaps in our past?) then a new
species with a sufficiently large, viable population can exist de novo.
It is very much looking as though this is the true origin of new species.
If this is so, and if a new virus comes along which we preferentially
incorporate in our DNA, rather than kill or be killed by it, then a new
human species could arise. This, of course, would be a very rare event. In
our past, we are talking of something like 250,000 years at least between
distinctly different hominin species -- homo habilis, homo erectus, etc.
But a new virus could come along tomorrow and thousands, or tens of
thousands, of a new human species could appear nine months later! If
perhaps it had a larger brain then this would set the cat among the pigeons!
Keith
Keith Hudson, Saltford, England
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