Manimals, Sticklebacks, and Finches
In tomorrow’s New York Times I have an article about the origin of species–or rather, blocking the origin of species. The evolution of a new species can be a drawn out process, taking thousands or millions of years. First populations begin to diverge from each other. Later, those populations may become divided by significant reproductive barriers. Even after those populations have evolved into separate species, they may still be able to produce hybrids in the right conditions. In some cases, those hybrids may remain rare and the two species will remain intact. In other cases, the species may collapse back on each other.
The article looks at two animals in which speciation appears to be going in reverse. One is three-spined sticklebacks, which have evolved into two easily distinguished different species in 11,000 years in six separate lakes in Canada. In one lake, an introduced crayfish appears to be driving the two species into a single hybrid swarm. …
I find it interesting to ponder this research in the wake of the hominid-ape hybrid research I wrote about last week. Our ancestors diverged from the ancestors of chimpanzees roughly six million years ago–very roughly according to recent studies that suggest millions of years of gradual separation, perhaps even with some hybridization after the lineages split. Scientists can only look back at that split by looking at the genomes of humans and other apes. But sticklebacks and Darwin’s finches can offer some clues to that delicate process of parting ways.
Once again, biology is messy and not-so-clean. Where it’s easy to think of sharp distinctions, the world really consists of blurry ones. Stop binary thinking.
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