THE YEAR 2009 is a double anniversary — 200 years since Charles Darwin’s birth, and 150 years since he published Origin of Species.
Scientific American has just published an issue devoted to the the subject of evolution, with several articles on Darwin and his theory. The first, Why Everyone Should Learn the Theory of Evolution, is a bit of a fluff piece, as are some of the others.
Then there is Darwin’s Living Legacy–Evolutionary Theory 150 Years Later , which offers a good, although highly generalized overview of Darwin’s accomplishment. Excerpts, with bold added by us:
Ruminations on evolution — often musings on how only the fittest prevail — carry an ancient pedigree, predating even Socrates. The 18th and 19th centuries produced fertile speculations about how life had evolved, including ideas forwarded by Darwin’s grandfather, Erasmus Darwin, who lived between 1731 and 1802.
Darwinian evolution was the first capable of withstanding rigorous tests of scientific scrutiny in both the 19th century and beyond. Today investigators, equipped with sophisticated cameras, computers and DNA-sampling tools thoroughly alien to the cargo hold of the Beagle, demonstrate the continued vitality of Darwin’s work. The naturalist’s relevance to basic science and practical pursuits — from biotechnology to forensic science — is the reason for this year’s worldwide celebration of the bicentennial of his birth and the sesquicentennial of the publication of his masterwork, On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life.
Darwin’s theory represents a foundational pillar of modern science that stands alongside relativity, quantum mechanics and other vital support structures. Just as Copernicus cast the earth out from the center of the universe, the Darwinian universe displaced humans as the epicenter of the natural world. Natural selection accounts for what evolutionary biologist Francisco J. Ayala of the University of California, Irvine, has called “design without a designer,” a term that parries the still vigorous efforts by some theologians to slight the theory of evolution. “Darwin completed the Copernican Revolution by drawing out for biology the notion of nature as a lawful system of matter in motion that human reason can explain without recourse to supernatural agencies,” Ayala wrote in 2007.
The process of theory building crept along at an almost glacial tempo. From his readings of Lyell, Darwin took the idea of gradual change in the geological landscape and reasoned that it must also apply to biological organisms: one species must beget another. The recognition of biology’s mutability was shared by some other evolutionary thinkers of the day. But it was conceived as a scala naturae — an ascending ladder in which each lineage of plant or animal arose by spontaneous generation from inanimate matter and then progressed inexorably toward greater complexity and perfection.
Darwin rejected this straight-line progression in favor of what is now called branching evolution, in which some species diverge from a common ancestor along separate pathways, contradicting the prevailing view that there are fixed limits on how far a new species can diverge from an ancestral one. Darwin recalled that three species of mockingbird he observed in the Galápagos could be traced to a single colonization of a related species he had observed in Latin America. His sketch of a branching “tree of life” is the only illustration in Origin of Species.
Yes, but how does it happen? Let’s read on:
The concept of a tree of life still begged a “how” for evolution, a gap that led to Darwin’s most revolutionary idea, the theory of natural selection. From reading the work of Thomas Malthus, Darwin recognized that populations tend to grow quickly, thereby overwhelming limited resources. He also had an obsession with animal and plant breeding. He would visit agricultural markets and collected plant catalogues.
In 1838 he came to the realization (shared at first with only a few friends) that the natural world, instead of deliberately choosing favorable traits as if it were a cattle breeder, has its own way of addressing a bulging demographic that threatens to exhaust an ecological niche. From the vast hereditary diversity within a given species, natural selection blindly weeds out those individuals with less favorable traits: in essence, Ayala’s concise “design without a designer.” Moreover, if two populations of the same species remain isolated—one in a desert, the other in the mountains—they may over long periods develop into wholly separate species, no longer able to breed.
Darwin had avoided discussion of human evolution in Origin of Species, but his The Descent of Man, and Selection in Relation to Sex attributed human beginnings to Old World monkeys, an assertion that also offended many and made its way into cartoonish newspaper caricatures of the scientist as half-man, half-ape. Even in the 1860s Darwin’s cousin, Francis Galton, and others had begun to complain that modern society protects its “unfit” members from natural selection. The distortion and misunderstanding of Darwinism, from Nazi ideologues to neoliberal economists to popular culture, have yet to cease. American novelist Kurt Vonnegut once remarked that Darwin “taught that those who die are meant to die, that corpses are improvements.”
It’s a good article, providing the background for Darwin’s work. Click over to Scientific American and take a look.
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