So, I'm on the bus this morning, reading Dawkins' The Greatest Show on Earth, and he spends a couple of pages explaining how, before Darwin, everyone thought species had essences; they were natural kinds, which of course makes it very hard to imagine how one species could turn into another. But Darwin showed us how to think of species in terms of populations containing lots of variation, and the average of the distribution can shift over time until it's so different we no longer call it the same species. This narrative about how the idea of "species" changed (as opposed to the species themselves changing, if you get my meaning -- like, I'm talking in a meta-level here...oh, never mind), Dawkins credits to biologist Ernst Mayr, who explained it all to us back in the 1950s.
Then the bus gets to work, and I spend a few hours doing workish things.
And when I return home this evening, there is awaiting me a padded envelope which opens to reveal this book:
...by this guy.
And of course John wastes no time (as in: right in the Prologue, before we even get to Chapter The First) telling us that Mayr got it all wrong, in fact the whole book is about how wrong he was, almost no one was an essentialist, ever.
It's fun when that kind of thing happens.