Morality: Don't be afraid to dream

A LUCID dream has three phases. First you experience the dream as reality. Then you recognise it as a product of your mind. Finally, you gain the power of control.

Morality is proceeding along similar lines. We have long thought of moral laws as fixed points of reality, self-evident truths rooted in divine command or in some Platonic realm of absolute rights and wrongs. However, new research is offering an alternative, explaining moral attitudes in the context of evolution, culture and the neural architecture of our brains.

This apparent reduction of morality to a scientific specimen can seem threatening, but it can be explained. By unmasking our minds as the authors of our morality, we may be better able to affect the narrative arc towards a happy (or happier) ending.

One way to do this is to recognise the ways in which evolution has shaped morality. Social psychologist Jonathan Haidt asked students at the University of Virginia in Charlottesville to imagine a brother and sister engaging in secret, consensual, protected sex. Would that be wrong, he asked? Most thought so.

However, when asked why, the students floundered. Protection meant no threat of disabled children, and secrecy brought no possibility of disclosure or embarrassment (in the short term). The pair had no conscience or regrets because it was through mutual agreement and consensual. So how is it wrong?

Perhaps incest is simply an arbitrary taboo, passed on through religion, law, parents and peers or is it a societal taboo instilled in less enlightened time to restrict the genetic weakening effect of inbreeding.

Debra Lieberman, an evolutionary psychologist at the University of Miami in Florida, tested these rival hypotheses with an ingenious experiment (Proceedings of the Royal Society of London B, vol 270, p 819). She considered the ways in which evolution could have built in a "sibling detector".

For older siblings, it is easy: just watch who your mother gives birth to and who she raises as her own. For younger siblings a more subtle strategy is needed: note how many years you live in the same household as other children.

Lieberman asked over 1000 people how much the thought of incest disgusted them, and the results were clear as day: older siblings were uniformly disgusted by the thought, while younger siblings' disgust was a linear function of years of co-habitation.

Then Lieberman showed that unrelated children reared together in Israeli kibbutzim develop sexual aversions according to the same factors, even though there is no cultural taboo against relationships between them.

Finally, she showed that people's moral outrage when contemplating others engaging in incest was predicted by the level of aversion they would feel towards intercourse with their own siblings, again based on those two factors. In short, it seems that the moral injunction against incest is a product of a specifically evolved mechanism to prevent sibling sex.

Theories about the biological evolution of morality have been around for some time, but a very recent area of research is into the cultural evolution of morality. Just as we inherit genes from our parents, we inherit values from cultural sources, and just as genes adapt to environments, values evolve to match the structure of social life.