In reply to Dave Perry:
> Correct me if I'm wrong but the last time I read up on this only one sperm is required. I'm sure we've got plenty spare as back ups......
Apparently not, human males, though you wouldn't know it from our population hover on the brink of infertility, something around a 5% decrease may be enough to render a human male. In contrast, a rat can take a 95% decrease before they become infertile, now that's a reserve tank!
The issue of human sperm count decreases is nothing new, and it is not exactly clear if it is real at all, and if it is, we've no idea of the cause. For some it is the so called gender bending chemicals!