December 16, 2008


Darwin's Living Legacy--Evolutionary Theory 150 Years Later: A Victorian amateur undertook a lifetime pursuit of slow, meticulous observation and thought about the natural world, producing a theory 150 years ago that still drives the contemporary scientific agenda (Gary Stix, December 15, 2008, Scientific American Magazine)

When the 26-year-old Charles Darwin sailed into the Galápagos Islands in 1835 onboard the HMS Beagle, he took little notice of a collection of birds that are now intimately associated with his name. The naturalist, in fact, misclassified as grosbeaks some of the birds that are now known as Darwin’s finches. After Darwin returned to England, ornithologist and artist John Gould began to make illustrations of a group of preserved bird specimens brought back in the Beagle’s hold, and the artist recognized them all to be different species of finches.

From Gould’s work, Darwin, the self-taught naturalist, came to understand how the finches’ beak size must have changed over the generations to accommodate differences in the size of seeds or insects consumed on the various islands. “Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends,” he noted in The Voyage of The Beagle, published after his return in 1839.

Twenty years later Darwin would translate his understanding of finch adaptation to conditions on different islands into a fully formed theory of evolution, one emphasizing the power of natural selection to ensure that more favorable traits endure in successive generations. Darwin’s theory, core features of which have withstood critical scrutiny from scientific and religious critics, constituted only the starting point for an endlessly rich set of research questions that continue to inspire present-day scientists. Biologists are still seeking experimental results that address how natural selection proceeds at the molecular level—and how it affects the development of new species.

Darwin’s famed finches play a continuing role in providing answers. The scientist had assumed that evolution proceeded slowly, over “the lapse of ages,” a pace imperceptible to the short lifetime of human observers. Instead the finches have turned into ideal research subjects for studying evolution in real time because they breed relatively rapidly, are isolated on different islands and rarely migrate.

Since the 1970s evolutionary biologists Peter R. Grant and B. Rosemary Grant of Princeton University have used the Galápagos as a giant laboratory to observe more than 20,000 finches and have shown conclusively how average beak and body size changes in a new generation as El Niños come and go, shifting climate from wet to arid. They have also been able to chronicle possible examples of new species that are starting to emerge.

The Grants are just one among many groups that have embarked on missions to witness evolution in action, exemplars of how evolution can at times move in frenzied bursts measured in years, not eons, contradicting Darwin’s characterization of a slow-and-steady progression. These studies focus on the cichlid fish of the African Great Lakes, Alaskan sticklebacks, and the Eleutherodactylus frogs of Central and South America and the Caribbean, among others.

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.

Theologians work can largely be considered to be done given that the foremost defender of Darwinism is himself a Designist:

Posted by Orrin Judd at December 16, 2008 2:21 PM
blog comments powered by Disqus