on defining species

[acroyear]

Coyotes, Species Definitions, and Speciation : Mike the Mad Biologist:

One of the reasons I've learned to stay away from debates about "what is a species" is that practical species definitions (i.e., something we can use to classify critters) do a lousy job of describing the process of speciation, while conceptually sound species definitions (ones that describe the speciation process) are usually miserable when you actually try to classify organisms. Why? Because delineating species implies (and requires) sharp biological breaks that might not exist.

Comments

[katrinb.livejournal.com]

Which is one of the creationists' favorite arguments, "If species evolve into other species, that means that at one point a child is born of a completely different species, and by the definition of species, they have no one to mate with."

Ignores completely that the whole no-interbreeding thing is a human-created definition, a bright line placed by us for our own mental use where no bright line really exists (like the definition of an exactly- eighteen-year-old person as a voting adult citizen, and a seventeen-year-and-364-day-old person as a child). There are slow gradations - varieties, types, etc.- between species. And plenty of known examples of animal or plant species that extend over large geographical areas, where each group looks and behaves quite like the groups next to them, and can and will interbreed with the groups next to them, but where groups farther apart look quite different, won't interbreed, and would, if not for the intervening varieties, be classed as different species. If you substitute "time" for "distance," it becomes pretty obvious how speciation happens.