Is odour is a matter of fact or opinion?

We have our body odour to thank for lots of things. One person we interviewed on this programme earlier this year, was John Pickett from Rothamsted Research, who has actually bottled "eau de human", and specifically bottled those components coming off your skin that mosquitoes hate! So there are some people in the population that exude odours that mosquitoes really cannot stand. And some people carry those genes, which enable them to make those chemicals, whereas others don't. By bottling those chemicals you can turn it into the world's best insect repellent, and that's what he's done. So I think that in that respect, body odour is extremely useful and not only mosquitoes but it works against the Scottish Biting Midge as well. People also done research on how attractive women find the smell of sweat from men. They get them to wear a shirt for while and the women sniff them and I think they've shown that you're actually more attracted to people who are less genetically similar to you. This is definitely true in mice and the studies are very robust. We know that if possible, they will try to find a mouse partner who is as genetically different from themselves as possible. If you put two mice together and they're brother and sister, and you don't give them any choice then the female will mate with the male, and have pups with her brother. But if you then introduce a third mouse, which is genetically totally different from the first two mice, then the female can abort her babies and re-mate with the different male. Mice have this very strong and well developed sense of smell, and we know that the smell receptors are on the same chromosome as the structures that control how the immune system works. So we think that mice can use smell as the surrogate marker of how your immune system is working and so you can use that smell to guide you as to how different you are genetically from someone, and therefore go for someone who is as genetically different to you as possible which should make you healthier. The problem is that we humans tend to have very well developed frontal lobes in our brain. Which means we're very social, we think things through very carefully and we're very, very likely to get the argument skewed by things like social pressures, and likes and dislikes and how big someone's wallet is.