(from an interested layman)
I was thinking a bit about how the first steps in speciation would go, in case of geographic seperation for example. The first question that came to me was whether inbreeding would be a problem, and whether maybe there are evolutionary mechanisms against it apparent in animals.
Does the isolated population have to be of minimum size to not "collapse" under degeneration?
Do we recognize some sort of evolved "aversion" within related animals to mate with each other, or are they totally blind for this? What is known about how humans fare in this respect, if any social or cultural influences are eliminated. Are brothers and sisters or other close relatives (in general) somehow not attracted to each other, like they can be to not related individuals?
This sounded to me like an interesting topic..