Would you want to know when you are going to die, or at least when the physical decrepitude of age will overwhelm you? It seems that there is a message, if not exactly to the main, at least to sophisticated molecular analytic engines, written in your cells.
For the most part, we live longer than our individual cells. Cells are constantly breaking down, being shed, and replaced by the products of new cell division. There is a problem with the replication of chromosomes that takes place prior to cell division however, in that the enzymes that mediate it cannot fully replicate the ends of the chromosomes. Consequently, in order to protect us from losing genes with every division, our chromosomes are equipped with special end caps, called telomeres. Cell division does shorten these telomeres however, and this limits the number of times a cell can divide. Consequently, every cell division is a step toward ultimate doom.
You might want to ask why the Intelligent Designer would play such a nasty trick on us, aside from pure mean-spiritedness. The best answer, I think, is that it is a line of defense against the uncontrolled cell proliferation of cancer. If a group a cells starts proliferating out of control, it will run into the blockade of telomere shortening, and die – unless, of course, as cancer cells do, it learns the trick for avoiding that trap.
Back to our story though, it seems that companies are now advertising a test that will check the length of your telomeres, and hence predict how long you might live if you manage to avoid other catastrophes. You can get the good or bad news for 400 Pounds.