The secret (and ancient) lives of houseplants

houseplant

What mysteries do houseplants hold? What can houseplants tell us about the environments we live in? Check out my new post on the evolution of houseplants at the Your Wild Life blog

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Darwin’s monsters

Re-reading Darwin on this rainy day, I’m struck by all the monsters. In On the Origin of Species, Darwin wrote:

 Nor shall I here discuss the various definitions which have been given of the term species. No one definition has as yet satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species…We have also what are called monstrosities; but they graduate into varieties. By a monstrosity I presume is meant some considerable deviation of structure, generally injurious to or not useful to the species.

Darwin’s concept of natural selection depended on a comparison to artificial selection. [A topic I’ve written about at Sci Am.] In the first chapter of Origin, Darwin discusses examples from plant and animal breeding. Darwin saw two types of variation in the bred world: abrupt changes or “monstrosities,” and small changes. Darwin thought that small, gradual changes were most important to natural selection, and therefore to evolution. Natura non facit saltus – nature does not make jumps.

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Darwin’s focus on the utility of certain biological variations echoes the philosophies of some of those who influenced him, like Thomas Malthus and Adam Smith. In an ordered world, it made little sense to have a sixth finger: “we see peculiarities arising and becoming attached to the male sex in our domestic animals (as the wattle in male carriers, horn-like protuberances in the cocks of certain fowls, &c.), which we cannot believe to be either useful to the males in battle, or attractive to the females.” If not useful (and so selected for naturally) or attractive (and so selected for sexually), a trait was, to Darwin, a monstrosity unlikely to be inherited.

Lesser known than Darwin’s theory of natural selection — the struggle for life, the Law of Mutual Struggle — is Russian biologist Karl Kessler’s 1879 Law of Mutual Aid. Presenting to the Society of Naturalists of St. Petersburg, Kessler outlined a theory of cooperation. According to Kessler, the struggle for existence as formulated by Darwin put too much emphasis on competition, ignoring cooperation among individuals. Some species worked together for protection from enemies, he argued, or to secure winter provisions. Peter Kropotkin promoted Kessler’s theory, writing in 1902 that it was under-population, not over-population, that characterized the Russian tundra, and that, contrary to the Darwinian’s worldview, species on the tundra did not experience “fearful competition for food and life.”

Daniel Todes argues that Russian scholars like Kessler and Kropotkin viewed Darwinism (or, rather, Malthusianism) as a “purely English doctrine” in that it was preoccupied with practicality and competition.

Biological variation within species continues to be a main topic in ecology and evolution. It remains difficult to imagine inefficiency in the biological world, to see form without function. Are fiddler crabs bluffing, or are some traits just not practical? Have we forgotten to consider Darwin’s monsters?

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