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Christians hit on the idea of celebrating Christmas on 25 December at
some time in the 4th century AD. Although they had no idea on which day
Christ was born, their choice was not a coincidence; the date was already
a pagan festival, which marked the birth of the sun god at the winter solstice.
The Christians were then struggling for power with the long-established
Roman religion and needed something to keep their followers busy while everyone
else was enjoying a holiday. So 25 December has been passed down from antiquity
to the present as a feast of the nativity – with certain discreet improvements
in the identity of the birthday god.

Christmas is only one example of a cultural rule, or symbol, that has
been passed down through the generations, in this case in societies culturally
descended from Rome. It is the sort of thing that tempts us to extend the
theory of evolution from genetics to human culture. Even the way the early
Christians competitively schemed to select the festival date is reminiscent
of the struggle for existence that drives biological evolution. And in some
respects human cultures do indeed change like biological species.

Cultural evolution occurs because we possess a mechanism for replicating
cultural ideas and rules from individual to individual; New ÐÓ°ÉÔ­´´ is
part of that mechanism. If ideas can be propagated through a human population,
some will do so better than others, and will predominate. They may propagate
better because of their inherent appeal to the human brain or, as some anthropologists
would prefer to say, because they are supported by powerful groups in society
which have an interest in promoting a certain ideology. Christianity did
not take off until Constantine made it the state religion of the Roman Empire,
and it was propagated as much by patriarchal mob violence as the perversion
of vulnerable circuits in the brain. But whatever the reason, cultural evolution
is the result.

If the analogy between genetic and cultural evolution holds, the same
theories and concepts should explain both. One controversial idea, from
Richard Dawkins, the evolutionary biologist, is that religion is a ‘virus
of the mind’, a cultural analogue of the agents that give us flu or AIDS,
or indeed of the rogue instructions that wreck computer programs. Dawkins’s
suggestion belongs to the provocative, blasphemous tradition of other philosopher-scientists
of the 20th century such as Bertrand Russell and Peter Medawar, and so should
be left to run free. But for those of us with a professional interest in
cultural and genetic evolution, the idea of religion as a virus is interesting
for another reason: it assumes that it is possible to distinguish between
cultural parasites and everything else in a culture.

With biological organisms we can certainly distinguish between a population
undergoing evolutionary change and one being infected by parasites. But
the distinction is difficult, or even meaningless, for a culture. Consider
a cultural change, such as the spread of television this century. It spread
at the expense of other information and entertainment media, such as radio
and newspapers: but does that make television a virus – a virus of the eyes
and ears – or was it just a normal cultural evolutionary change? From a
newspaper proprietor’s viewpoint, television may seem to act like a giant
cultural tapeworm. The television industry channels cultural energies, which
would otherwise be consuming newspapers, into another medium, just like
a tapeworm sucks energy out of its human host and converts it into more
tapeworms. On the other hand we could reason that the change was merely
another cultural change, of the kind constantly taking place within cultures.
It was like light-coloured moths evolving into dark-coloured moths; the
latter replaced the former because they were better adapted to the environment
and not because they were parasites

Bloomsbury narcissism

So the distinction between parasitism and evolutionary change for human
cultures requires some further thought. Maybe the textbook definitions of
parasites will help? Parasites do have well-known properties: they reduce
their hosts’ chances of survival, and cannot themselves survive independently
and die out with their hosts. Cultural analogies in this case tend to be
politically charged. For some people, the military-industrial complex is
parasitic, while for others Bloomsbury narcissism (‘I’d rather betray my
country than my friends’) is. If you know the real purpose of a culture
(or part of one), it is easy to recognise parasites; but once you start
to define a culture in terms of all the symbols and ideas that are propagated
through it, the parasites and the hosts become inextricably confused. A
culture does not have an identifiable purpose in the same way that the human
body, for example, evolved to propagate human DNA.

Difficult as it is to distinguish a cultural virus from the ordinary
currency of the human mind, some objective investigation is possible. We
can look back, for example, to the origin of the human brain and ask what
it first evolved to do. We can be sure natural selection originally provided
us with our brains because they enabled our ancestors to leave more offspring
than did the competing protohumans at the time. But did our cerebral circuits
evolve to carry rational, even scientific, thoughts about nature and society,
or to mystify them with religious meaning?

No doubt our ancestors needed some rational skills to survive, but the
answer must be that the human brain evolved more as a religious than a rational
organ. Rational science is a minority interest. Philosophy was invented
by the Greeks, but scientific thought appears only sporadically in European
history before the 16th and 17th centuries. Religion, however, is a cultural
universal, and probably is the preferred mode of brain action of most people
today.

It is therefore likely that the first human brains evolved to impose
symbolic meaning on the external world, and the scientific virus later infected
a minority of their descendants, where it now flourishes in nerve circuits
that originally evolved to carry other ideas.

If you accept this conclusion, it leads on to questions such as: Why
are we not more rational? Why are we not more robotic? Imagine our ancestors,
perhaps a million years ago somewhere in East Africa. The population contains
individuals possessing two brain types: one type is rational, the other
religious. I think of the rational protohumans as ‘robotic’, not in the
sense of only being capable of a few simple and inflexible responses, but
in the sense of being governed only by a rational control system.

Conjuring with hocus-pocus

Logically, in these conditions, natural selection should favour the
rational robots. Scientific rationality is more efficient than irrational
superstition; it actually does transport people through the air and put
them on the Moon. In the struggle for existence, the rational protohumans
would have reasoned about affairs objectively and done whatever necessary
to produce the best result. They would have built weapons whose efficiency
was guaranteed by the laws of physics while their more spiritual contemporaries
were conjuring with hocus-pocus. In a real conflict, the practical efficiency
of science would have been decisive and, as a result, there should be more
robotic brains and fewer religious ones in the next generation.

Appealing though this argument is, it must be wrong, because it predicts
the wrong winner. We are descended from the religious brains, not the robots.
What else was going on? I do not know the whole answer, but perhaps in a
Darwinian struggle for existence, religious enthusiasm can ‘crowd out’ rationality.

Consider how natural selection works on fecundity. In any population
that lives for a significant length of time, on average each pair of parents
leaves just two surviving offspring. That is as true of rabbits, or cod
fish, as it is of humans. You might think the best way to achieve that average
would be for everyone to produce two offspring. Alas, that cosy state of
affairs is unstable. If it ever existed, natural selection would favour
a mutant individual who produced, say, 20 offspring. This mutant would spread
through the population and soon everyone would be producing 20 offspring.

Yet, on average, only two of these offspring would survive. Death by
starvation, overcrowding and competition for resources would inevitably
claim the rest. Natural selection would continue to favour increases in
fecundity until the population was practically destroying itself in the
effort to produce two surviving offspring from each pair. Only then is an
equilibrium reached. High fecundity ‘crowds out’ replacement fecundity.

Now return to the ancestral humans. Suppose they were a population of
rational robotic people. They calculate objectively how much effort to put
into fights and other kinds of conflict and cooperative action, both inside
and outside their group. They will do fine until they encounter mutants
with a tendency to religious enthusiasm.

These religious newcomers value land not only for the resources it provides
but because it has meaning to them: it is the home of their gods and must
not be occupied by unbelievers. They take irrational risks in fights because
the gods look after them in battle, and reward them later in the event of
death. Some of them may even exterminate their enemies when there is nothing
rational to be by it, especially if their god resembled the bloodthirsty
lord of the Old Testament, who was subject to fits of genocidal bad temper
and, if the record is to be believed, was the worst mass murderer in history.
Religious enthusiasm could then crowd out rationality.

I am not talking about the vulnerability of our own brain circuits to
superstition; I am discussing natural selection between two whole brain
types in our history. Nor am I repeating the familiar argument (which may
well be correct) that religion causes us to identify with, or sacrifice
ourselves to, the good of our local group. Evolutionary theorists are suspicious
of this argument because it is based on ‘group selection’. Furthermore,
a robot could theoretically calculate the optimal amount of cooperative
self-sacrifice and achieve (more elegantly) the same outcome as the religious
zombies. So how did religious protohumans outcompete their robotic contemporaries?

Rationality alone is vulnerable because our reasons, and objective evidence,
for almost everything are exceedingly poor. In the great mechanical universe,
individual humans are almost irrelevant and we need something more than
robotic reason to goad us into self-exertion. So if we rely on reason alone
there is nothing to stop us asking ‘Why bother’?

A religious believer will suffer no such doubts. Natural selection then
favours people who go beyond the evidence, or believe more than they ought;
it puffs us up with self-importance, and makes us believe that we are the
chosen creatures of supernatural entities who are actually interested in
us. According to this argument, it is an important property of a religion
that the gods should be interested in us. The doctrine of the ancient Greek
philosopher Epicurus – that we do not know whether there are any gods or
not, but if they exist we can be sure they will not be in the least interested
in us – has a certain sense to it, but as a religion it has been a complete
historical flop. We can see why. It would be useless at crowding out rationality,
and would be unstable against more anthropocentric creeds.

Perhaps a rational robot could be built that would resist the mutant
religious fanatics, but I am not sure. The clear advantage of rationality
seems to be contradicted by the way most of our conspecifics prefer to use
their brains. And whatever the reason why natural selection did not favour
rational robots, the apparent priority of religion leaves little doubt about
the evolutionary purpose of our brains. From an evolutionary point of view,
if anything is the cultural virus, it is science.

Mark Ridley teaches anthropology and biology at Emory University, Atlanta.