Asked by: Brian Fogharty, Birr, Ireland
Some species don’t bother, and don’t seem to suffer, but mice, sand lizards and some shorebirds certainly do. For example, Black-legged kittiwake chicks are much more likely to die if their parents are closely related to each other, but this doesn’t happen often because females try to select unrelated males. Wild house mice rely on specially evolved proteins in their urine to sniff out and avoid mating with their close relatives.
In many social species the trick is that one sex, usually the female, leaves the group at adolescence. That way they can’t mate with their own family. Presumably this dispersal behaviour evolved because females who left home had more offspring who would in turn carry on behaving this way.