I'd then like to discuss the likelihood of millions of years of ancestors all coming together at exactly the right time, and combining exactly the right egg and sperm on every occasion to lead up to the birth of a person who would later post on the internet under the name 'vmancha'.  20 or so million sperm per 'coming together' taken to the power of millions of years of generations...  I may need a bigger calculator for this one.  Can we delay it a bit?

Nice.  Well that saves me on a calculator

This is a hotly contested question, with at least two main theories debated in the literature. I can't really do either of them justice, but I can provide a rough overview.

The first theory is that when a poorly designed spermatazoa fails to inseminate, it swims into a small pouch in the left labia maiora (or if unable to do so, is guided to it by a group of symbiotic batcteria.) Once there the sensitive nervous system - as discovered by evolutionary psychology and creation science, only men like sex, so all the nerve endings on the vagina are clearly not for pleasure - collects precise data on each sperm so interred and transmits it to the brain for analysis during REM. Once the analysis is concluded, the information is relayed down to the bad sperm hangar, where symbiotic viruses who live off the electrical impulses thus sent convert it to RNA form, which they inject into the analyzed sperm. In addition to containing the analysis, this tells the sperm to swim back into the penis the next time intercourse occurs. (Of course, if this is a different male, he would be effectively stealing sperm R&D work from the last guy. This is why sexual jealousy evolved.) Once this happens symbiotic viruses in the male devour the returned sperm and start turning out copies of the messenger RNA, which they inject into the right teste, which is in charge of sperm design. Through a system so intricate and specifically complex that it could not possibly have evolved by naturalistic means, this feedback from the female is loaded into a sort of RNA database which updates based on each model report that comes back, and which produces innumerate copies of yet another RNA strand (newly issued each sperm production cycle) which are then injected into to germ cells just after they've undergone mitosis. Each recombined set of chromosomes attempts to form a TNA (tririboneucleic acid) with the injected RNA; if they fail, indicating a set of set of genes judged suboptimal, they recombine again. (There is some interesting stuff going on here with a sexual conflict of interests, where the female's feedback RNA may have been optimized for tricking the male into selecting genes that would most help our her genes rather than his, but usually this works to the benefit of both, preventing combinations that would result in birth defects. This system is so effective, in fact, that experimental theologians have determined that 90% of birth defects result from the supernatural intervention of God, most often as collective punishment of the human race for its poor stewardship of the environment.) The same genetic strand also guides the transformation of the germ cell into sperm according to the most recent specifications. If possible, the energy used to "wind up" sperm for their swim is ATP harvested from proteins broken down from the consecrated body of Christ (this is why Catholics have so many children.) At the end of this cycle, the male has several million lean, mean, and sleekly designed sperm, like the latest line of Mercedes. 

The other theory is that, through some yet-unspecified mechanism, males whose sperm doesn't work don't have many offspring. 

I knew what was coming, but that final sentence was amazingly well phrased.

Once again, a demonstration of what I have been saying all along:  theists, ID proponents, creationists, Christians, whatever ... are more interested in being right than doing right.  Winning the argument is more important to them than getting to the truth.