Dawkin's books had a profound effect on my world view; his
arguments are completely convincing.
However, there are a couple of questions that are not
adequately addressed (for me) in his books and have worried
me for a long time. I am hoping for some insight; my
apologies if these are regular topics in this ng.
In at least the first two cases (and possibly all three),
they relate to characteristics which appear to be bad for
the individual but good for the species. They also appear to
have elaborate mechanisms which prevent individuals from
mutating to the benefit of their offspring but detriment of
the species. This doesn't line up very well with a narrow
view of the selfish gene. Allow me to explain ....
1. Why are men's testes on the outside, where they are prone
to accidents, instead right in the middle of our bodies
(like ovaries), where they are far safer?
The standard biological arguemnt is that sperm production
cannot occur at internal body temperature. While this is
true, it doesn't sound like the underlying reason. Of all
body processes, in all animals (many of which have different
body temperature), why is it that the only one which needs
to be a few degrees cooler is sperm production? With such a
substantial evolutionary pressure on keeping the testes in
working condition, why there is no biological mechanism
which allows sperm production (like egg production) to occur
at normal body temperature?
My alternate premise is that our testes are on the outside
to expose them more to radiation and hence increase the
mutation rate. This is good for the species but bad for the
individual. This would explain why they need to be kept
cooler. Moving the testes inside the body would require two
independent changes, changing their location and allowing
them to function at body temperature. A mutation which
caused the first but not the second would render the
individual sterile. A mutation which caused the second but
not the first would provide no evolutionary advantage.
Accordingly, the requirement to keep the testes cool
effectively prevents a change (moving the testes inside the
body) which benefits the individual but disadvantages the
species as a whole.
2. Why do we die, indeed, why do we age at all?
may as well die, so we can re-phrase the question to say
"why does menopause occur in animals" if desired.
Maybe there is just no way of building a biological machine
which doesn't wear away. However, this answer doesn't really
explain the wide range of life expectancies in different
animals, and the fact some organisms (eg bacteria) don't die
of old age as such.
Death (or menopause) is clearly not in the interest of the
individual, but is clearly in the interest of the species,
as it frees up resources for subsequent (possibly fitter)
generations. Maybe all the complicated things that happen
when you age are actually adaptations actually "designed" to
make you die and age. There are multiple mechanisms
involved, to eliminate the chance of an individual having a
benign mutation which makes them live far longer or not age
at all, an adaptation to the massive benefit of the
individual but huge disadvantage of the species. In this
model, cancer and heart disease are actually positive
adaptions which help make room for future, possibly fitter,
descendents. Again, the irony is that these mutations are
specifically not to the individual's benefit, or indeed the
gene (or gene combination) that causes them. Its hard to see
how a gene which causes the organism to die could be a
"selfish" gene.
3. How come I produce X and Y chromosome sperm in
equal numbers?
Assuming each couple produces 2 children, with a mix of X
and Y sperm each couple will have equal numbers of male and
female children at each generation - 1 boy 1 girl at
generation 1, 2 boys 2 girls at generation 2, 4 boys 4 girls
at generation 3, etc.
An individual who produced only Y chromosome sperm would
produce only boy children. Assuming this is an inheritable
characteristic, so would his 2 male children. So instead of
equal numbers of boys and girls at each generation, this
mutation leads to an exponential increase in males - 2 at
the first generation, 4 at the second, 8 at the third etc.
Again, this mutation would be for the benefit of the gene
that expresses it - as it spreads exponentially through the
population - but to the detriment of the species. I accept
that eventually an equilibrium would be reached where
females have more reproductive choices, and so this gene
confers no advantage. This would occur when there are twice
as many males as females, because at this point the double
probability of having a boy (ie absolute certainty) is
offset by the halved chance of reproducing at all (shortage
of females). But there is no sign of humans having a
mutation which significantly increases the percentage of Y
sperm that are produced, despite the fact that such a
mutation would rapidly spread through the population.
Could this be another example where there are mutations
which are beneficial to the individual but detrimental to
the species, and so there are multiple mechanisms to prevent
individuals from having adaptations to their benefit?
And if this is so, doesn't this move us in the opposite
direction from Dawkins? He essentially took survival of the
fittest (individual) and made it survival of the fittest
(gene). These arguments are essentially survival of the
fittest (species)? A gross simplification, but I am sure you
get the idea.
Thanks for reading this post. These things have bugged me
for a long time. The ideas of Dawkins are as close to a
religion as I have (as in "why are we here" and "where did
we come from"😉; its a bit sad if your personal religion
can't also answer the question of "why do we die" ....
Peter Webb