If you can get in close enough, checking out someone's smell is a valuable way of finding Mr or Ms Right. Despite our aversion to smell and our much reduced olfactory areas in the brain (at least compared to dogs and horses) we are in fact surprisingly sensitive to it. Newborn babies and their mothers can identify each other by smell alone within hours of the birth – which is one reason why we now like to make sure that the baby goes straight on the mother's breast as soon as it is born. This is something that we share with most other mammals. In sheep and goats, the mother learns to recognise its newborn young by smell within 24 hours, and in the following days will allow only that lamb to suckle. And the lambs themselves learn to identify the right mother to suck from in the same way, though they are, perhaps understandably, a bit slower and it usually takes a couple of days' exposure to the mother's smell.