Una in Croydon asked:
If female mammals have mammary glands, then why do male mammals also have similar mammary glands? Do all males have them and why bother having them at all if they donít do anything?
Itís an evolutionary thing. If you look at how we develop in utero, for the first few weeks male and female babies look absolutely identical. Itís only subsequently that you start, under the power of the hormones pumped out, to change and alter your anatomy. But because you develop a lot of these surface structures and appearances when youíre very early on in development, youíve got them whether you need them or not. There is one example that Iíve managed to find thatís a male and uses itís breasts to potentially breast feed as they certainly lactate. Thatís a Dayak fruit bat and they live in Indonesia. The male produces about a tenth of the amount of milk that the female does.