June 21, 2008


How Darwin won the evolution race (Robin McKie, 6/22/08, The Observer)

In early 1858, on Ternate in Malaysia, a young specimen collector was tracking the island's elusive birds of paradise when he was struck by malaria. 'Every day, during the cold and succeeding hot fits, I had to lie down during which time I had nothing to do but to think over any subjects then particularly interesting me,' he later recalled.

Thoughts of money or women might have filled lesser heads. Alfred Russel Wallace was made of different stuff, however. He began thinking about disease and famine; about how they kept human populations in check; and about recent discoveries indicating that the earth's age was vast. How might these waves of death, repeated over aeons, influence the make-up of different species, he wondered?

Then the fever subsided - and inspiration struck. Fittest variations will survive longest and will eventually evolve into new species, he realised. Thus the theory of natural selection appeared, fever-like, in the mind of one of our greatest naturalists. Wallace wrote up his ideas and sent them to Charles Darwin, already a naturalist of some reputation. His paper arrived on 18 June, 1858 - 150 years ago last week - at Darwin's estate in Downe, in Kent.

Crossbreeding to Save Species and Create New OnesMARK DERR, 7/09/02, NY Times)
Though definitions vary, in general hybrids are created when different species interbreed -- or, if not species, then animals or plants from distinct lineages or with distinct adaptations to their environment. Hybridization has been found in a long list of species: mice, leopard frogs, sunfish, insects, Darwin's finches in the Galápagos Islands, hummingbirds, birds of paradise, willow, iris, oak, sunflower. White-tail deer and mule deer hybridize, as do domestic cattle and bison, cattle and yaks, wolves and dogs, wolves and coyotes, and coyotes and dogs.

The new research on hybridization is casting new light on evolutionary processes and raising questions about biodiversity and the preservation of endangered species. In the mid-1990's, wildlife biologists saved the endangered Florida panther from extinction by crossbreeding it with the closely related Texas cougar. That program opened the way for the use of hybridization in saving endangered species.

Most species cannot crossbreed because the genetic, behavioral and ecological barriers are too great to overcome. An elephant will not interbreed with a lion or wildebeest, nor will a wolf mate with a bear or a prairie dog with a squirrel. Still, the new findings indicate that hybridization between species does occur and can sometimes produce new species -- calling into question the longstanding view that a species is a population of interbreeding organisms that is reproductively isolated from other species.

And the finch will lie down with the bird of paradise...

Posted by Orrin Judd at June 21, 2008 7:10 PM
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