Mad rantings about politics, evolution, and microbiology. Comment policy: say what you want, but back it up with an email address. I don't like anonymous trolls.
There's a really interesting article in last week's NY Times magazine about global warming and the spread of weeds. There was, however, one jarring note, and it had to do with an incorrect definition of natural selection (italics mine):
"There's no such thing as natural selection," Ziska confides. He is not, he hastens to explain, a creationist. He is merely pointing out that the original 19th-century view of evolution, the one presented by Charles Darwin and Alfred Wallace, is obsolete. Their model presented evolution as a process taking place in a nature independent of human interference. That is almost never the situation today -- even at sea, where less than 4 percent of the oceans remain unaffected by human activity, according to a recent article in the journal Science.
I don't mean to pick on Ziska--he's doing excellent and important work--but that's not correct, at least for the last few decades. Artificial selection occurs when the fitness criterion--that is, what trait or phenotype will have higher survivability or reproductive output--is directly chosen by the experimenter. In the case of the weeds, if we were delibrately trying to grow better weeds--that is, mowing down rice biovars that aren't sufficiently 'weedy'--that is artificial selection. Simply changing the environment such that weedy biovars will do better is natural selection because we are not specifically trying to enrich for rice that have the trait of 'weedy-ness.'
Keep in mind that one can use natural selection for very applied purposes, and the boundaries will get fuzzy, but in the case of global warming, this is clearly natural selection. Besides, in a materialist sense, we are just another species of critter.
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The concept of "artificial selection" presupposes a separation of man from nature that I do not accept. Therefore the distinction between natural and artificial selection has always seemed to me arbitrary.
Posted by: Tegumai Bopsulai, FCD | July 2, 2008 12:10 PM
Natural selection is not goal oriented. Artificial selection is. I still do not understand why this distinction is so difficult.
Posted by: walkers2@mac.com | July 2, 2008 12:24 PM
Artificial selection is only goal-oriented from a human perspective. If we breed members of an animal species to produce more meat, or of a plant species to produce tougher fiber, the population of the target organism is simply responding to selection pressure, the same as it would have if the change in environment did not result from human agency.
Artificial selection is the use of natural selection principles, by humans, as tools. As such, it deserves its own description via human language, but there's nothing about it that's sharply divided from more general cases of natural selection.
Posted by: Julie Stahlhut | July 2, 2008 1:41 PM
Walker hits the nail on the head.
Posted by: Steve | July 2, 2008 1:54 PM
@walkers2: I think "goal-oriented" still has shady borders. Does it count as goal-oriented when humans first started actively planting seeds (with no understanding of heredity)?
Animals have various patterns of eating (or trampling) plants that affect how the plants evolve and how their seeds are spread. Humans also interact with plants, but our goals are often the same (food) as the other animals -- we just happen to understand a bit more about how our actions will affect the food we get, and we can act accordingly & consciously... but we are not the only species that has "domestication" relationships with other species.
Posted by: Rob W | July 2, 2008 2:02 PM
A simple useful example is finding that weeds adapt to cities, yet nobody is deliberately breeding weeds for improved urban survival rates.
Another is that beavers used to be daytime animals but now, thanks to hunters, they've become nocturnal.
Posted by: 6EQUJ5 | July 2, 2008 2:49 PM
"Their model presented evolution as a process taking place in a nature independent of human interference."
Does this mean that humans do not evolve? That would explain much of the folly of humans.
Posted by: Paul Thoreau | July 2, 2008 3:53 PM
I'd say the goal-orientation is an important place for distinction in some cases. Ultimately, yes, one may be able to say that our artificial selection is still "natural" in the sense that everything we do is ultimately a deterministic result of the action of the Universe. However, when humans consciously breed other species, they develop traits that could not be sustained without our intervention -- such as the inability to breed naturally, or very high dietary requirements.
Both types of selection use the principle of natural selection, but the pressures put on the organism are different enough that "artificial selection" should at least be a subset of "natural selection" (along with "sexual selection"). Maybe we can call the more common, survival-of-the-fittest stuff "survivor selection" or somesuch?
Posted by: GAC | July 2, 2008 4:13 PM
Darwin leaped from artificial to natural selection to make comparisons.
An interesting sleight of hand move.
The theory can't stand without equivocations and maneuvers such as that.
And GAC, if everthing we do is ultimately a deterministic result of the action of the universe...an undemonstrable faith claim on your part...then why bother?
What will be will be.
The fit will survive, the weak will perish, and a hundred years from now none of this crap on these blogs will be remembered.
Posted by: Emanuel Goldstein | July 5, 2008 4:50 AM
"...and a hundred years from now none of this crap on these blogs will be remembered."
And thank Jeebus for that!
Posted by: Tyler DiPietro | July 6, 2008 12:44 PM