There’s an interesting article in this week’s Nature (well, strictly last week’s now, but still the most recent one I have here), on research into the neural basis of disgust, and its links to ethical judgements. (Nature 447 (2007), 768-771) It would seem that, when people judge things to be ethically disgusting, they are using the same parts of the brain, and in much the same way, as when they judge faeces to be disgusting. There’s also a lot of interesting work on the human tendency to punish undesirable behaviour, and on the origins of compassion and cooperation, although that doesn’t appear in this week’s issue. It all appears to be perfectly natural.
This is a problem for ethics, because instincts hardwired into us by evolution in order to promote the spread of our genes in future generations are not generally considered to be the right sorts of things on which to found a system of ethics. Ethics should be grounded on universal truths, not a set of feelings cobbled together by the essentially random process of evolution because they were helpful when it came to surviving on the prehistoric African steppes.