I can’t believe Laelaps beat me to this (shows how on the ball he is) but he’s just noted a paper that I watched getting written, and discussed in detail with Chris Glen, a very smart and talented young paleontologist, before I got to. So I will now, before he goes and does a better job.
Chris and his advisor Michael Bennett have come up with a possible way to test the “trees down or ground up” controversy about the origins of flight. That is, they have some independent evidence that early birds were basically ground dwellers, but that there was, as there is now, a mix of lifestyles – it doesn’t follow that a bird today must always live in trees or on the ground. What is needed is a way to identify the actual lifestyles of modern birds, and apply that test to early birds.
So, Chris thought of using the morphology of the middle digit of the bird foot, and in particular, the curvature of the toe claw, as a guide. He studied some 3000 specimen bird claws, if memory serves, from 249 modern (Holocene) birds and identified those that were obligately ground dwelling, those that were obligately arboreal (never came down to the ground) and those that were mixed. It turns out that the lifestyle closely correlates with the degree of curvature of the claw. Hence, it is a reliable guide in early birds.
I just love this kind of scientific reasoning – at its best it puts Sherlock Holmes to shame, and I have seen a few cases first hand. What is really interesting about Chris’s work is that it also has wider epistemological application: about how to make historical inferences of the past states of things, about how to test one theoretical issue with independent theory – Chris came up with a theory and tested it extensively.
I don’t have Chris’ larger essay, part of his PhD, to hand, but he has lovely diagrams that show how to measure curvature without being approximate or subjective – he uses actual anatomical anchor points that are common to all the species he is testing (I think that woodpeckers and ratites might be extremes; I’ll have to ask Chris). Apart from anything else, he can draw like a… well, pro.
And the conclusion? Early birds exhibit the morphology of mostly ground dwellers. What that means for the flight issue is a whole nother matter. Watch this guy’s work. I I have been privileged to have coffee and chat about this with Chris, and I know he’s going to make some more contributions.