Origin Ch.10: Darwin the geologist 1

This post is part of a series on The Origin Of Species.  It was originally posted on the old blog in feb 2009, during the Darwin 200 celebrations.

Chapter ten is supposed to be a response to the objection that if evolution were true, one ought surely to be able to reconstruct its historical course with our fossils. It’s an objection that can very easily be addressed, on two fronts — firstly, that we can reconstruct much evolution with fossils (though this is a lot more true today than it was when The Origin was written), and secondly that the fossil record is a long way from perfection. Even when Darwin was writing, it was well established that only a tiny fraction of individuals will ever present themselves for fossilisation; that some species will never — can never — end up represented in the fossil record; that fossils have been and are being destroyed without ever being recorded by science; and that the overwhelming majority of fossils will remain hidden in the ground forever.

So if it’s so easy to rebut the objection, why does Darwin devote a whole chapter to it? Probably because he’s a geology nerd. The imperfection of the geology record isn’t the real point of the chapter, Darwin just wants an excuse to chat about rocks. And rocks are important in the story of Darwin and evolution for reasons other than the fossil record. You can find these reasons in reading Voyage of the Beagle or the letters he sends back to mentor John StevensHenslow from the ship. Darwin isn’t just looking at the botany and zoology of South America on the voyage, he is spending at least as much time documenting the geology. And why shouldn’t he? Why do mere stamp collecting — or beetle collecting — when you can work in a field that has the beginnings of explanatory theories? Why look at isolated cases when you can look at processes and events?

Geology had taken those first steps to maturity. Rather than being the unaltered creation of the almighty, the Earth had become an unimaginably ancient planet whose stasis could not be relied upon, and ideas like these did seem to impress the young Darwin. And Darwin went on to take the stamp collecting field of biology and turn it into a modern science with a core overarching theory. And yet it would be nearly another half century before a core theory — plate tectonics — would complete the transformation for geology.