...Hm. Actually, a lot of the pokemon who can produce eggs don't make sense, don't you think? Porygon is also supposedly man-made - or at least isn't a biologic creature as such - but they seem to have no problems reproducing either. The only creatures I've heard of who seem to have that issue are the "legendaries", as I'm led to believe there's only one of each.

Which makes me wonder if the legendaries are all immortal, or if there's just a severe underestimation of their population...