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RETURN TO THE WORLD SCIENCE HOME PAGE Do species “learn” their way into existence? Aug. 12, 2005
But researchers lately have begun considering some slightly different accounts, which strip a bit of control from such blindly random forces. No, these ideas have nothing to do with “intelligent design”—the recently popular claim that a divine force is in charge, which almost no scientist accepts as science. Rather, the new thinking hands a bit of control to the creatures themselves: it claims that new species can to some extent “learn” their way into existence. And far from being a product of religious fervor, it stems from Darwin’s own evolutionary theory. Partly, though, it arose as an attempt to solve a problem that plagues that theory: it can’t quite explain how one species evolves into two. This branching process, called “speciation,” seems to be nature’s chief way of producing new species, but how it happens is unclear. Explaining it is easy if a permanent barrier such as a river splits up a population. Then the creatures on each side would evolve their separate ways, becoming separate species. But what if there’s no barrier? Then constant mating between members of a population presumably mixes up the gene pool, blurring differences and preventing the splitup. In the past two years, some researchers have advocated one solution that gives a key role to a simple form of learning. Animals can colonize new habitats,
they propose, then learn to recognize and exploit those habitats. This might help break populations into genetically isolated groups that can evolve into
separate species. A second proposed solution also assigns a role to learning, and has also gained currency in recent years. This idea claims that creatures learn to recognize and prefer mating partners more like them. This might prevent random mating that would otherwise mix up gene pools and stop speciation. Some experimental evidence backing the notion has been published. But this model assumes some genetic separation has already occurred by the time these mating preferences arise, raising what some researchers describe as something of a chicken-and-egg problem. Thus, advocates of the theory have described it as a way speciation could be completed, rather than begun. Beltman and colleagues, by contrast, claim the learning of habitat features might help drive the whole process. They propose a three-step recipe for speciation. First, creatures colonize new habitats. Second, they adapt to them, in accordance with traditional evolutionary theory—mutations arise, those few that help organisms thrive in their habitat spread through the population, and the population gradually becomes better suited to its habitat. In the third step, the creatures start mating less often with others of their species, who occupy different habitats. Enabling all this to occur is a tendency for many animals to prefer to live where they grew up, wrote Beltman and Patsy Haccou, also of Leiden University, in a paper in the May issue of the journal Theoretical Population Biology. This is true of many animals, including fish, insects and birds, they argue, and it is a simple form of learning. “Females normally produce their young in the same habitat as they grew up in,” they wrote. “They may, however, accidentally produce their young in another habitat,” they added. Moreover, “The young resulting from ‘accidents’ will learn features of the new habitat.” “Because of this, they will most likely mate with other individuals exploiting the habitat, and adult females will tend to produce their young in the new
habitat,” they continued. “Through such processes, the colonization of a new habitat may eventually lead to speciation.” Send us a comment on this story, or send it to a friend
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