Thursday, April 10, 2008

Evolutionary theories...hurt my head

It's been some time since my last post...

Anyway, I've been busy trying to write a manuscript on the evolution of bite forces using finches and cats as case studies. One thing I've found out through this process is that, it doesn't matter how sophisticated a method you use, nor does it matter how great you think your results look, what matters is your ability to tie that into a broader perspective of evolutionary theory. And I've sadly realised, that either I don't have the brains, or the imagination, or the creativity, to write anything remotely interesting in the grand scheme of evolutionary theory. Evolutionary theory's the interesting end-product of all this functional morphology and phylogenetic comparative methods anyway, and if you can't do that, then you're screwed...

But I don't intend to be lazy and give up. At the same time I've been trying to be greedy. So I've been trying to read as much evolutionary theories as I can...


....and my head hurts...

2 comments:

Zach Miller said...

Finches (supposedly) developed their stronger bite forces due to shortages of their preferred seeds on one island, and those with strongER bite forces had access to tougher seeds, and thus a wider range of food (because the tougher bite can crack tough AND soft seeds). I don't know how helpful cat bites would be, because cats are doing completely different things with their mouths than tyrannosaurs or even finches.

That is, cats use their "front" teeth to cut jugulars and bleed prey to death--cats don't just go "hog wild" on prey items--they plan it out and are very deliberate. After the kill is made, the cat actually bites into the food from the side of its mouth and chews with its enlarged molar teeth.

Tyrannosaurs BROKE STUFF and didn't worry about chewing. You're more likely to find a connection between prey species across tyrannosaur evolution than between tyrannosaur bite forces and modern analogues.

Think about this (and I'm sure you have already): Dwindling diversity in herbivore selection may have had something to do with the tyrannosaurs' evolution of bone-crunching bite, just like the finches on the Galapagos. Ceratopsians had thick bones and shield-like pelves. Can't attack the head. Duckbills were easier prey, sure, but their diversity was being affected, too. And tyrannosaurs were likewise being rubbed out. Suddenly the tyrannosaurs without bone-crunching bites (like Albertasaurus) couldn't survive because their prey selection was down to ceratopsians (can't win) or giant hadrosaurs.

Does that make any sense? I'm useless without a drawing pad.

Mambo-Bob said...

Well, this paper's got nothing to do with tyrannosaurs and will be focusing on if there are any patterns of evolution in relative bite forces through phylogeny or not - i.e. if a certain taxon changed its bite force relative to its size, then is that change dictated by phylogeny or not? So it's a macroevolution/trends in evolution style study. Nice simple analyses with the potential to discuss trends in evolution or the lack there of...

I used finches firstly because there are bite force and body size data readily available in the literature and secondly for historical significance. Similarly, there are data, including well-resolved trees, readily available for cats. I also have quite a bit of personal observations and measurements on cat skulls so it makes sense to use cats.

I was planning on including theropods but I need to consider a few things about my theropod bite force estimates before I can do anything with them, so they're on a hold for now.