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.Plants can only dabble in eating animals if there are enormous numbers of plants around that don’t, and they find it difficult to compete with animals because they’re sedentary.If you’re an eater, it’s a great advantage to be able to get around—waiting for your food to come to you is obviously a second-best strategy—and an organism needs so much energy to get around that if it’s going to do that, it might as well be a specialist eater.“So how come this world is so rich in organisms that have kept their ability to fix solar energy in spite of the fact that they can eat and get around? The purple worms don’t even seem to make strenuous efforts to get out into the sun when they can.They lurk in the shadows like any other stealthy predator.How can that make sense?“Well, I can only see one way in which it might make sense.If the super-slugs keep chloroplast-analogues they don’t bother to use on a day-to-day basis, there must be times when they do need to use them.Rare times, maybe, but vital times—times when that energy-fixing capability is so vital that it’s carefully sustained through all the times when it’s not.And that’s where the exotic reproduction has to come in.”He looked away as a sudden movement caught his eye, but it was only something falling from the canopy.He looked back before Ike moved the camera.“The most important difference between life on Earth and life on Ararat, alias Tyre, is that sex isn’t the only way of shuffling the genetic deck so as to produce the variations on which natural selection works.Here, sex involves cells within a chimerical corpus rather than whole organisms.You could say that all the local organisms are actually small-scale colonies of continually cross-breeding individuals.And they’re probably all emortal.That doesn’t matter much to the simplest ones, because they never live long enough to die of old age; they always get eaten long before they reach the limits of their natural life spans.The more complicated ones are a different matter.”Matthew hesitated again, but this time it was purely for dramatic effect.Ike understood that, and stayed focused.“Earth’s ecosphere was shaped by what Bernal Delgado used to call the sex-death equation.The essence of life is reproduction, but there are two kinds of reproduction.There’s the kind by which organisms make new organisms and the kind by which organisms reproduce themselves.The cells of your body are continually replaced, so that every eight years or so there’s an entirely new you, almost as good as the old one but not quite.We humans—and I mean we in a narrow sense, because there’s a new human race on Earth now that doesn’t have this particular disadvantage—deteriorate like a chain of old-style photocopies, each image becoming a little more blurred than the last.Eventually, we die of growing old, if we haven’t already been killed by injury or disease.In the meantime, though, most of us make a few new individuals, by means of sexual reproduction.We die, but the species goes on—and we owe our existence to the fact that natural selection used to work on the new individuals our remoter ancestors made, weeding out the less effective ones.We owe our intelligence to the slow work of natural selection, which perfected the union of clever hands, keen eyes, and big brains that pushed our forefathers ahead of all their primate cousins.“To us, that all seems perfectly natural, and so it is—but it needn’t have been that way.Here, evolution took a slightly different path.Here, sex is routinely confined to the kind of reproduction by which the local equivalents of organisms reproduce themselves.I say the local equivalents of organisms because they’re not the same as Earthly organisms in the sense of being genetic individuals.They’re compounds: chimeras.That seems odd, because they don’t look like the chimeras of the Earthly imagination: they’re not compounds of radically different species, like griffins, and they don’t seem to go in for dramatic metamorphoses—at least, not on a day-to-day basis.But they do reproduce in the other sense, because they have to, and they are subject to the kind of natural selection that drives an evolutionary process, because they have to be.We can see that, just by looking around, because we can see perfectly well that this ecosphere is as complex as Earth’s, and that the logic of convergent evolution has produced all kinds of parallel bioforms.It may seem puzzling at first that we can’t see the second kind of reproduction going on, because no alien visitor to Earth could possibly miss it if he hung around for a year or two, but when you think about it carefully, you can see that it’s much less puzzling than it seems.”Matthew looked up at the canopy and gestured with his arm.Ike looked puzzled for a moment, but then he caught on [ Pobierz całość w formacie PDF ]