The Meme Machine

A MEMETIC THEORY OF ALTRUISM 149
some kind of altruistic behaviour, and explained that ‘Despite the principle of
“survival of the fittest” the ultimate criterion which determines whether G will
spread is not whether the behaviour is to the benefit of the behaver but whether
it is to the benefit of the gene G.’ (Hamilton 1963, p. 355). This means that
altruistic behaviour can spread in a population if animals are altruistic towards
their own kin. The nearness of the relationship determines just how much it is
worth paying for the possibility of aiding the spread of the gene. Instead of
basing everything on the idea of individual fitness, the important quantity
becomes ‘inclusive fitness’, which takes into account all the indirect ways in
which a gene can benefit (Hamilton 1964). The mathematics can get extremely
complicated in real-life situations, but the principle is simple.
Genes are invisible. A monkey that is going to share some food cannot be
sure whether the other monkey is really her sister or not, and certainly cannot
look inside and find out just which genes the two of them have in common.
However, this does not matter for the principle to work. Monkeys that, in
general, share resources with kin more than with non-kin will get more of their
genes into the next generation. How they achieve this may vary, and probably
involves various simple heuristics such as ‘share with another monkey you were
brought up with’ or ‘share with other monkeys that look, smell, or feel like your
mother’ or ‘share most with monkeys you spend most time with’. Depending on
the lifestyle of the animals concerned, different heuristics will work better than
others. They work not by making the monkeys calculate sums, but by giving
them feelings that make them act appropriately. The same applies to us. In
other words, people ‘execute evolutionary logic not via conscious calculation,
but by following their feelings, which were designed as logic executers’ (Wright
1994, p. 190).
We humans love our children (most of the time) and however much we are
annoyed by our brother or despise our aunt, we still find it natural and
unsurprising that we give them birthday presents, send them cards, or care more
about them than some person we met in the street. But the theory of kin
selection explains far more of the detail of family dynamics than just that,
including battles over weaning, siblings competing for their parents’ resources,
and other forms of family strife as well as love.
Another success for biology has been reciprocal altruism. Darwin (1871)
speculated that if a man aided his fellow-men he might expect to get aid in
return. A hundred years later Robert Trivers (1971) turned this speculation into
the theory of reciprocal altruism, explaining how selection might favour animals
who reciprocated friendship, for example, by sharing surplus resources in good