It seems that each of us is the improbable result of a long series of chance events. The last one being when an egg is fertilized by a spermatozoon with either an x chromosome or a y chromosome.
Now then, several questions arise. First, are all of a woman’s eggs identical? If not, then why not. Also, do all of a man’s spermatozoa consist of two and only two types? If not, then why not.
I’m particularly interested in the question of the spermatozoa. If there are only two possibilities, then it seems that it is inevitable that any male or female born will be the same person regardless of which spermatozoon fertilizes the egg as long as it has either an x or y chromazome. But then fraternal twins, as long as they are the same sex, would be identical. They’re not. And all brothers should be identical also and they’re surely not. If they’re all somehow different, then there is the possibility any one of a couple of hundred million different people being conceived.
Maybe each conception of identical eggs and spermatazoa do not result in identical zygotes. I suspect this is true, but why is it so?