The Crocodilian Past

It had a head like a bullet with jaws, the body of a crocodile and 52 serrated teeth, and it lived 135 million years ago. But perhaps the most surprising thing about this ancient crocodile - whose name is Dakosaurus andiniensis and whose discovery was announced in the current issue of the journal Science - is that there must also have been a world to which it was peculiarly fitted, a niche to which it had adapted. That world is as long gone as Dakosaurus itself. Like all such prehistoric beings, confronting us out of the depths of time, Dakosaurus is yet another reminder that most of the life that has ever lived on Earth has gone extinct.

This crocodile seems peculiar to us because it looks so unfamiliar, so unexpected, the stuff of aquatic nightmares and bad Hollywood movies. But of course we would have looked peculiar to it, too. This is the deep, perspectival problem of life itself. The world we live in - including its modern crocodiles - looks normal to us because it happens to be our world. In our entire lives, most of us encounter only a minute fraction of the life forms present on Earth at this moment. And so we are barely cognizant of the strangeness of now - never mind the strangeness of 135 million years ago. Everyone knows Crocodylus acutus - the modern American crocodile. And yet you don't have to stare at it very long before it too looks strange, and you begin to wonder what it's doing in the world to which it is adapted.

The problem of familiarity and perspective is one barrier that keeps some people from grasping the truth of evolution. The more you confront the diversity of life forms in existence - all the ways of getting a living on this planet - the easier it is to grasp the malleability of life itself under the pressure of natural selection. Then something like Dakosaurus comes along, reminding us that the record of all the life forms on this planet is far from complete, and far stranger than we could ever have guessed. We would be at an utter loss to make sense of this diversity, of all the ways life presents itself, without the theory of evolution to explain it.