redrikki

I'm reading a book on recent research on dinosaur evolution (The Rise and Fall of the Dinosaurs by Steve Brusatte - apparently he has a book on bird evolution coming out soon and I'm definitely picking that up when I can) and it is blowing my miiiiiiind.

For example!

Did you know birds don't have hollow bones because they evolved them to fly? Birds have hollow bones because dinosaurs (saurians in particular - like Brontosaurus type creatures - but some of the other lineages as well) evolved them because it gave them an edge on growing large without being overly heavy, cooling themselves, and efficiently extracting oxygen from the air to support their enormous bodies. The super-efficient lungs that birds have were also a dinosaur adaptation to being big in hot climates, not a bird adaptation to flight. So basically, birds have ultralight bones and efficient lungs not because they evolved them to fly, but because dinosaurs needed these things in order to grow huge, and this turned out to be incidentally useful in radiating out into aerial niches when they began to evolve wings.

I also find it a fascinating experience to read this paleontology book when I've done so much reading on archaeology as a hobby interest. Archaeology books go into great depth on careful excavation techniques, sifting all the tiny bits of material and keeping everything in its proper location, and how incredibly tragic it is that so many sites of the past were excavated carelessly and so all of that information on the relative positioning of discoveries and small bits of material is lost ...

Meanwhile, paleontologists: so we took our hammers and started hacking up this rock formation to get the bones out. :D Also a local rancher sold us a dinosaur skeleton he found!!

(I mean I'm exaggerating a bit and the huge time difference is important, but also, lol.)

Another thing I was thinking about in one particular chapter, though the book doesn't address it specifically, is something I've thought about before, which is that we assume some creatures are primitive representations of what their kind used to look like, when in fact they are perfectly well adapted to their current niche, and their ancestors looked nothing like that. Alligators and crocodiles are the thing I was thinking of here - they look primitive, with those sprawling legs and inefficient means of walking, but in fact, early crocodiles hundreds of millions of years ago had their legs under the body and could sprint like a greyhound. (Which is terrifying, by the way.) They look like they do now, not because they could never run - they could! - but because other, more efficient dry-land runners out-competed them and they lost the running ability and retreated into the amphibious predator niche that they currently occupy.

Another example of this, not from this book - recent research on the human evolutionary tree suggests (at least according to one book I was reading a while back on the Miocene period) that the ancestor of both humans and chimpanzees was a sort of generalist creature, a couple of tens of million years back, that could both climb trees and walk upright. Humans ended up adapting to the walking/striding niche and losing the tree climbing, while chimpanzees did the opposite, adapted to climbing trees and became much less efficient at moving about on the ground. So rather than descending from a chimpanzee-like tree climber, we and chimpanzees are both specialized creatures who do not resemble our common ancestor all that much.

I just love this kind of thing.