I've been meaning to check in on this thread. It's a very interesting article to be sure. The role of hybridization in evolution is very cool. I did some research last year into the Carolina Chickadee and its close relative, the Black-capped chickadee. The two species interbreed, but only in a narrow band of territory where their habitats overlap. This narrow band does fluctuate quite a lot, and probably has shifted north as climate changes. I was convinced for a time that I was seeing some of the hybrids in Franklin, NC, where we used to live. Alas, it was all very inconclusive, and now we live in Maryland.
The article suggests hybridization was probably a factor with the evolution of homo sapiens, that there was a gene flow between several early hominids, which might potentially answer a lot of questions about our origins. As the author says, "To be human, then, is to be a multispecies mongrel."
Hybridization is also another example of how evolutionary theory continues to evolve
well beyond Darwin's original framework. I don't think it's really a surprise to anyone that evolutionary theory is more complex than Darwin envisaged. Of course, I've also read a lot of Stephen Jay Gould, and that helped me understand that there are probably many mechanisms that drive speciation, perhaps many still not very well understood.
By the way, the article inspired me to subscribe to The Economist
. So thanks for that!