There has been much talk of human cloning recently. For some reason it was quickly banned in the United States and many of its puppets. Clones would offer many interesting outlets for study. The question of whether or not humans posses a "god given" soul could be answered. The extent to which genetics influences behaviour could be determined. The so called "twin phenomenon" could be studied on a far greater level. Why has all this research been precluded before it was even proposed? Mainly the first question, the people on whom this information would have the greatest effect are the one's who want it the least.
DNA is a somewhat like a computer program. Much like the binary sequence contains the information to build random number generators, JPEG images of "unnatural acts," and this document the DNA molecule contains a quaternary (Base4) sequence containing the information to build proteins, bones, and humans.
Interestingly there is only a finite number of bases in the human genome. Hopefully you remember from you algebra class that you cannot obtain an infinite set of variations when allowed only a finite set of choices. The meaning of that? There is a limited number of possible variations of the human genome.
This is a very large number of course. About 4^2000000000000. The problem with this raw number is that some of these possible variations is that some of the mutations could result in lethal results. A modification of a single codon could destroy an entire protein folding ritual. Thus: the number of possible variations is not the number of allowable variations. The true calculations should be based on genes, though these calculations would be much more difficult as the nature of gene interactions is not totally understood, but the fact remains: a finite number is the result.
What's the significance of a finite number of possible variations? Those variations represent humans. There is only a finite number of possible different humans. And this finite number is slated for all humans since the beginning of time 'til our eventual extinction. There are over 6 billion humans now at this moment. Most likely, at one time or another, your genome, and my genome, have come up before.
Interesting idea eh? Reincarnation, it seems, is true.