|
One succinct way to describe/pattern-match life is "a process that lowers its own internal entropy, by consuming negentropy sources and emitting waste entropy." Which is sort of to say "a process for bringing order out of chaos", but with the much more particular implication of repairing any internal insult that may occur to return to equilibrium. In short: life is that which maintains itself. With that in mind—and ignoring the fact that things that cause successful reproduction take precedence (so "suicide by mating" is okay)—most everything in a living being has the "function"—at least, in an adaptive environment—of working to lower that living being's internal entropy over some time-scale. And everything that isn't helping in that function—every part of the system that isn't serving the system—is itself exactly the entropy that a living being, as a system, is trying to either excrete, wall off, bypass, or xenometabolize. A completely benign bacterium trying to "keep to itself" in a host is, definitionally, still a parasite: its own self-maintenance increases the entropy of its environment, i.e. the host. And most every kind of host (other than the most primitive of marine microflora) has defenses for parasites, even of the most benign variety, precisely because "keeping to oneself" is still a net negative on the host. A body will only tolerate that which offers some form of symbiosis to it—things which aid the body in the goal of maintaining itself, giving back more than they cost to keep around. (Obviously, I don't mean to suggest a body will figure out how harmful a given bacterium is and decide how much to react to it. But rather, evolution will selectively adapt the host species to defend itself against anything that's a net negative—while not putting nearly as much pressure to create defenses for things that are symbiotic.) This applies to things besides parasites, too: "vestigial features" usually aren't, but are rather usually still of some minimal benefit: chickens and penguins can't fly, but flapping their wings still assists them in fleeing from predators. A feature that is truly no longer of any benefit to the species costs more to build and more to maintain than it's "worth", and so, if the relevant genome isn't horribly spaghetti-linked, the feature genes will simply become methylated and turned off after a few generations. It's quite accurate to say that any feature, any organ, any chemical in a body is there for a reason—or at least there for a function. |