Tuesday, November 24, 2009

150 Years of Evolutionary Theory

On this day in 1859, Charles Darwin's On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life was published for the first time. Even before Darwin's work, other scientists had speculated that existing species could be transformed into other species. Darwin drew from these concepts, but he advanced the idea that species are continually adapting in response to natural selection. Despite its vilification by creationists, evolution by natural selection remains the guiding concept of the biological sciences. Many bloggers are more qualified than I to discuss the implications of Darwin's work and how evolutionary theory has developed since 1859, so I will leave more detailed discussions to them.

Birders, however, should celebrate this anniversary as we are in a particularly strong position to appreciate the results of evolution. We do not necessarily think consciously about evolution when we go birding; in my own experience, I think about Darwin very rarely while I have binoculars around my neck. But among birds, we can observe the diversity of forms and behaviors produced by natural selection. Warbler species, for example, evolved to fill many specific ecological niches. One warbler species forages mainly among dead leaf clusters; another breeds only in jack pine forests of a certain age; yet another warbler with bark-like black-and-white streaking specializes in picking invertebrates off the trunks and limbs of trees. Whether we realize it consciously or not, these evolutionary adaptations help us to identify birds. That buzzy, insect-like call is likely to mean different sparrow species in a grassy field and a saltmarsh; the same goes for a trilled song heard in a swamp and a suburb. Without some awareness of these species' adaptations to ecological conditions, birding by ear and birding by GISS would be a lot more difficult.

Since On the Origin of Species is old enough to be in the public domain, there are many complete digital copies of this book available online. Try Literature.org, TalkOrigins, Bartleby, or Project Gutenberg if you want to read it.

For other evolution-related reading on this blog, see my review of Pilgrim on the Great Bird Continent, an article on the evolution of wood warblers, the announcement of a new crossbill species in Idaho, an analysis of the evolution of waterfowl genitals, and a more recent post on new research into birds of the Galápagos.