Like a Moth to a Flame

Richard Dawkins at a Q&A session after a lecture at the University of Liverpool on February 25th 2008.

"Religion is widespread at least historically, perhaps universal, and human specific. So my question to you is do you think religion or religious belief evolved in humans and if so did it confer an evolutionary advantage?"

As a Darwinian, I am among those who believes that anything that is very widespread in a species in some sense has an evolutionary advantage.  It wouldn’t be there if it didn’t.

So yes, I think the answer is that it probably does have an evolutionary advantage but having said that, we have to be a bit careful about what we mean. Because very often when biologists look at something and say: “What’s the evolutionary advantage of that?” it turns out that they are asking the wrong question.

It may be that what we are looking at is some kind of a by-product of something else which has an evolutionary advantage and we have chosen to focus our attention on the by-product, which is not the thing that in itself has the advantage, but which is a consequence of the thing that has the advantage.

The example that I use to introduce the idea of by-product, is the question: Why do moths commit suicide by flying into candle flames, or into electric lights?  You could say, what is the Darwinian survival value of suicidal immolation behaviour in moths and it would be pretty difficult to think of what the survival value of suicide is. However, it’s the wrong question.  Flying into candle flames is a by-product of something else. And probably what it is, is this. This may not be right but it’s a good theory for what’s going on. Insects are well known to use distant light sources as compasses. Day flying insects use the sun as a compass, night flying insects use the moon or stars. The reason it’s a good thing to have a compass is that it’s a good thing to be able to fly in a straight line, it doesn’t waste time and so on.

The reason it works is that celestial objects like the sun and the moon, being at optical infinity, the light rays from them are parallel and therefore a simple rule of thumb in the brain that says “keep the light rays at an acute angle of say 20 degrees” will cause you to fly in a dead straight line, but only if the light source is at optical infinity something like the moon. If the light source is a candle, then the light rays are not coming parallel from the candle, they are radiating out at close quarters from the candle. The rule of thumb “keep the light rays at an angle of 20 degrees to your flight” will cause you to fly in a logarithmic spiral into the candle flame. These moths are not committing suicide. They are doing a piece of behaviour that would be sensible for all the millions of years when the only lights you ever saw at night were celestial objects at optical infinity.

Now, I think that’s what religion is like. I think that religion is a by-product of probably several psychological predispositions, which in themselves have Darwinian survival value, but which have consequences (parallel to the consequence of the moth flying into the candle flame), have consequences which probably don’t have survival value.  But just as the moth doesn’t know that the candle flame is not at infinity but is close by, so those of us who have these psychological predispositions which would have been a good thing in our ancestral past (may still be a good thing) the consequence of leading to religious behaviour which may not be a good thing, doesn’t occur to us.

The kind of thing I’m thinking about is a tendency to obey authority in a child. It’s probably a good thing for a child to obey its parents, to believe its parents indeed, when its parents tell it things about the world, because the child is too young to know a lot of important things about the world and would die if it ignored its parent’s beliefs, its parent’s advice.

So good advice like “don’t jump in the fire”, has survival value. But the child brain, just like the moth brain, has no way of distinguishing the good advice like “don’t jump in the fire” from the stupid advice, like… “sacrifice a mongoose’s kidneys at the time of the full moon or the crops will fail”.

So, I suspect that religion may be a complicated set of by-products of psychological predispositions, each one of which itself has an advantage, but the religious by-product is either neutral or…  well we don’t even need to say whether it has an advantage, it doesn’t matter. The Darwinian explanation is sufficient if we postulate that the original psychological predispositions had survival value.