From Ronald Monroe
Port St Mary, Isle of Man
It’s nice to see the old group selection debate aired with a new twist in
your journal
(“The unselfish gene”, 25 October, p 28, and
Letters, 22 November, p 66).
What Dawkins and other “genetic imperialists” seem to neglect is that
selection can never be at the level of the single gene except under very special
circumstances; a clone of individuals in a homogeneous environment with some
individuals carrying a mutation in one gene. This seems unlikely apart from some
Moneran and Protoctistan populations.
For all other organisms it is the individual genome (organism or colony) that
is selected by evolutionary forces to survive or to be eliminated. When I finish
the evolutionary race behind the other runners do I blame my weak ankles, wobbly
knees or my propensity to overheat? Probably all of those, and more.
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If we regard the niche as an n-dimensional hypervolume we must describe the
species as an n-dimensional hypersolid. The degree of fit between the niche and
the species must then be a measure of the selective force acting on any
individual within a species. In an organism with a large number of genes the
contribution of any one gene to that fit must be comparatively small, and other
genes may compensate for some of the effects of that gene. It is individuals who
don’t fit their niche very well that are eliminated, along with their whole
suite of genes.
It is easy to take a critical single gene such as the one responsible for
sickle cell disease and show how it appears to have selective advantage or
disadvantage. But can we really say it brought no other genes with it? In
general terms there are few traits the possession of one of which confers great
selective advantage on its own. I am reminded of the giraffe article that
appeared in New Scientist recently. The success of giraffes depends not
just on a long neck, but on the possession of a number of other adaptations to
compensate for the effects of the high blood pressure such an elevated intellect
requires.
After that I must lower my blood pressure with a tot of good Celtic cultural
practice, the supposed predilectary allele which I know has run in my family for
some generations (judging by their behaviour). But is that because of the
Scottish and Irish social contexts of my family’s evolution, or has this allele,
all on its own, conferred some beneficial adaptive ability?
No. No person can be reduced to a single psychological or behavioural
dimension, nor the fitness of any species be determined by a single gene.
