William D. Hamilton: In His Own Words
Frans Roes, a journalist based in the Netherlands, had the following
conversation with William D. Hamilton in 1996.
by Frans Roes
William D. Hamilton
Frans Roes: Some of your ideas about how
natural selection might favor a form of altruism were foreshadowed in the
1930s by Ronald Fisher's writings on the distastefulness of some insects.
In what way?
W. D. Hamilton: Fisher realized that
if the insect is actually eaten by the predator in the course of the
predator learning to avoid it, then whatever made that insect conspicuous
to the predator is obviously disadvantageous to the individual being preyed
on. So Fisher reasoned that the only way you could see that kind of
selection getting started would be if the insects were gregarious, the
group were siblings, and the predator, having tasted one and found it awful,
were then to leave the rest of the group alone. The genes of the one eaten
would then be indirectly promoted. Fisher also realized that this was not
such a strong form of selectionnot as strong as if it were the
individual itself that had a form of protection. He made some remark about
the selection going ahead at half the speed [since siblings share 50
percent of their genes], and that was one key early statement of the
selection principle concerning the closeness of relatedness that I later
came to develop.
Frans Roes: In part two of your 1964
article "The Genetical Evolution of Social Behaviour," you describe
postreproductive behavior in two kinds of moths. What was the general
phenomenon being illustrated?
W. D. Hamilton: I noticed that
someone had written about the postreproductive life spans of two kinds of
moths. The author had noticed that the cryptic [well-camouflaged] insect
tends to die very soon after it has laid its eggs, whereas the warningly
colored ones [such as the distasteful monarch butterfly] often have a long
life after they have laid their eggs. Again, this could be
interpreted in terms of the kinship principle in a rather neat way. In
the case of the cryptic one, if there are any relatives around in the
neighborhood at all, it is advantageous for the moth to give up its life
as soon as it has finished its own main business, laying its eggs.
Because if it is around and the predator detects the moth and eats it,
then that is a step in the predator's learning to detect other moths,
perhaps including those that have not yet laid their eggs. So by causing
itself to die soon after it has laid its eggs, it is actually doing a
service to its cousins in the neighborhood. Quite the contrary holds for
the warningly colored one. Once it has laid its eggs, it is in a position
freely to use its warning colors to warn everyone it can. So it should
continue to live and wait, and actually expose itself to being tasted by
the predator, because that would be a step in teaching the predator to
avoid its relatives.
Frans Roes: In moths, both sexes
have wings, but in some other insects either the males or the females are
W. D. Hamilton: Gene dispersal is
a very crucial evolutionary phenomenon. For a female to sacrifice wings
without having some other way of dispersal for her offspring would be a
deadly mistake sooner or later. Where females have become wingless, there
is some other way in which they or their offspring are dispersed to other
localities. Most commonly they have a young stage, a larva, which is very
mobile. Either it may climb onto other insects or onto a twig and from
there be dispersed by wind. Often such larvae have long hairs that enable
them to balloon on the wind very satisfactorily. In some species the
wingless female is carried by the winged malein his arms, almost
literally. During this flight time he is mating with her, and finally he
drops her off in a place suitable for egg laying. As for the males becoming
wingless, if the male can inseminate a mobile female, then he doesn't have
to worry about wings too much, because his genes can be carried off by the
female. This often happens in cases where wingless males mate with their
close relatives. So I think we can find some sort of rationale for many
particular cases, but as far as I know, there is no very sweeping theory
that explains why in some groups there is male winglessness and in others,
Frans Roes: You went to Brazil in
1975 to study the fig wasp. What did you discover?
W. D. Hamilton: Actually, I went to
study life in rotting wood, but I ended up studying fig wasps instead. Each
fig is a little world in itself. Some species of male fig wasps have no
mouth and thus cannot eat; these are entirely fighting and mating
machinesa very strange kind of animal with a very short life. In this
incredible symbiotic pollination System, the males hatch out as adults from
the fig's gauflowers, and the easiestindeed the onlyfemales to
mate with are those hatching inside the same fig. Theory says that if the
males mate with their sisters, and their sisters are capable of storing
sperm, then you must expect the proportion of males to be cut down
drastically. A mother should do much better if she produces a lot of females
and just enough males to fertilize them. In that way she would get more
Frans Roes: Why do the male insects
of some species engage in fights to the death, while in other species the
males tend to bluff?
W. D. Hamilton: For fig wasps, there
is not much point in bluffing inside the fig, because there is no time to
"live and fight another day." Everything is over in a few hours, and if you
don't fight now and try to win, then you won't be given another chance.
I saw bluffing with the giant Chilean stag beetle. In all
the tournaments I held between males, it turned out to be the second-largest
one that was the overall victor. This suggests that those with the biggest
"tongs" were not actually as strong as they seemed to be. And they live in a
situation where I can imagine that bluffing would pay off. Stag beetles are
quite long-lived, and there are many flowers on the trees they could visit
where females are arriving, and so it might be worthwhile to pretend that
you are stronger than you are, in the hope that a rival male will go away.
Then the bluff would have paid off.
Frans Roes: You use a lot of
mathematics in your work, and you write, "I had realized from experience
that university people sometimes don't react well to common sense, and in
any case, most of them listen to it harder if you first intimidate them
W. D. Hamilton: Equations seem to
frighten a lot of people; if you come at them with a display of
mathematical strength, then they often back off. With me, you might call it
a kind of bluff. If you have a simple idea, state it simply and forget
about the mathematics. But often I use mathematics because I need to
straighten out my own ideas. I have a somewhat illogical brain, and unless
I put it through the mill of mathematics, I can continue to believe in the
impossible for a long time.
Frans Roes: How much mathematicsand
geneticsdo you need to know to understand evolutionary theory?
W. D. Hamilton: You do need to know
the basics of genetics. I always found that good old standard Mendelism
serves me quite well, and the modern ideas have not really changed the
picture very much. I also think that in the mathematical field, you just
have to know something about probability theory to understand how genes
work in evolutionary processes.
Frans Roes: A general question: Do
living organisms behave as if they want to pass on their own genes, or do
they behave as if each of their genes is trying to replicate itself,
possibly at the expense of other genes of the same genome?
W. D. Hamilton: This is a very deep
and difficult question. One's impression is that there is a conflict
between selfish genes, but largely it is being overridden by a kind of
democracy that has arisen in the genome. [This will] suppress this
intergene conflict, and the outcome is that the organism acts largely as a
Frans Roes: You write that
evolutionary ideas "turn out to have, or are perceived to have, the
unfortunate property of being solvents of a vital societal glue."
W. D. Hamilton: The glue that I am
thinking of is various myths that tend to hold societies together.
Religious people think that if people "believe" in evolution instead of,
say, the gospels, they will no longer be able to celebrate simple
honestyor kindly and warm feelings toward othersas
unequivocally "good." I think they exaggerate the danger, but they don't
exaggerate a nothing. There is a danger of that kind.
Frans Roes: How are evolutionists
trying to deal with this problem?
W. D. Hamilton: If you believe that
we evolved out of animalsare animalsand have the same kinds of
drives, it does not mean that we have to be selfish and inhumane. When you
fully work out the consequences of the rules of kinship and of
reciprocation, you will see that the outcome is in fact quite a moderate
kind of behavior, that it avoids evil and is as good in holding the society
together as are the religious myths. Indeed, under a rational theory, we
should be able to do better for human happiness by avoiding various naive
[ Frans Roes, "In His Own Words," June 2000, Natural History
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