The Meme Machine

‘AN ORGASM SAVED MY LIFE’ 125
produce the eggs and males the sperm – indeed this is the usual definition of the
sexes in widely diverse species. Eggs are large and contain food for the growing
embryo, so they are expensive to make, while sperm are tiny and relatively
cheap. Eggs are therefore made in smaller quantities and need to be guarded,
while sperm can more readily be squandered. In addition, many females also
provide a great deal of parental care beyond the provision of an egg, and it is
parental care that really makes the difference when it comes to choosing a mate.
The logic of parental investment was initially worked out by the biologist
Robert Trivers (1972), following Fisher (1930) who called it ‘parental
expenditure’. Trivers showed how the sexual behaviour of many different
species could be explained by considering how much resources each sex puts
into bringing up the offspring. This new understanding was then applied to
human behaviour by early sociobiologists. Humans are an interesting case,
complicated by the fact that our babies require intensive care for many years and
are still unable to fend entirely for themselves for years after weaning. Male
parental investment is high compared with other mammals, with males
providing food and protection for the family. However, male investment is still
much lower than female investment in both traditional and industrialised
societies. In existing hunter-gatherer societies women have been shown to
provide far more of the nutritionally valuable food for their children than men do
and to spend many more hours per day working. Even in our supposedly
emancipated Western societies some estimates suggest that women work on
average twice as many hours per day as men – that is, including paid jobs,
housework, and child care, This disparity, in parental investment can explain a
lot about human sex.
A human female can produce a maximum of roughly one baby a year in her
fertile years, amounting to perhaps twenty or twenty-five in a lifetime. The
highest ever recorded is supposedly sixty-nine babies, mostly triplets, born to a
nineteenth-century Moscow woman. However, human babies require enormous
amounts of care, and in traditional hunter-gatherer societies women probably
produced one about every three or four years, spacing the children, as huntergatherers
do today, by sexual abstinence, long lactation and sometimes
infanticide. The simple fact is that a woman cannot increase the number of
children she can successfully raise by mating more frequently or with more men.
By contrast a man can, potentially, produce a huge number of offspring. The
more women he can impregnate the more babies he will have, and he can more
or less rely on the mother to give them some care. Even if some do not survive
he will only have invested a few sperm and a brief (and probably pleasurable)