Like a stowaway who steals food from the crew at night, a B chromosome is a parasite; it can hurt the organism’s chances of reproducing, delaying the onset of fertility in females. But from the point of view of genes on the B chromosome, that’s okay; if they slightly reduce the number of hips that set sail, but manage to sneak onto all of them, they will do better than genes that play by the rules, getting excluded from half of the ships. It is these law-abiding genes that suffer from the shrinkage of the overall fleet.
Cultural evolution long ago supplanted genetic evolution as our key adaptive mechanism, and it has now put us on the verge of taking control of our genetic evolution, replacing natural selection with artificial, test-tube selection. And we’ll increasingly be steering the evolution of other species, as well.
All in all, the shape of life on this planet is now moving so fast via cultural evolution that evolution by natural selection is, for practical purposes, standing still.
Reklam
The fates of individual species may depend on the luck of the draw. But the properties they embody were in the cards—at least, in the sense that the deck was stacked heavily in their favor.
The cells that will form your egg or sperm were put aside for safekeeping; try as some mutant skin cell might, it will never get into the next generation, no matter how prolific it is.
Why do animals thus seclude their germ lines? In the view of some biologists, it is precisely to avoid this sort of parasitic mutiny; germ-line sequestration is an anti-cheating device—the functional equivalent of a technology of trust.
What is in an organic entity’s “Darwinian interest,” remember, is what aids the transmission of its genetic information. So if a bunch of cells have exactly the same genetic information, their Darwinian interests are by definition identical. Suppose, for example, that two cells face starvation, but cell A can somehow save cell B by committing suicide. The net effect of cell A’s “sacrifice” is to raise the chances that its own genetic information will reach the next generation—since, after all, its own genetic information is being carried by cell B.
Information is what allows life to defy the spirit, though not the letter, of the second law of thermodynamics. Information marshals the energy needed to build and replenish the structures that the entropic currents of time tirelessly erode—so that life can exist.
Reklam
Reklam