Tuesday, May 29, 2007

More On Ham's Creation Museum, Tyrannosaur Teeth And The Scientific Process

A reader, responding to my Creation Museum Carnival post on what Ken Ham’s Creation Museum won’t be telling kids about teeth, cautioned me that one argument in particular was weak and that Answers In Genesis views could not be so easily dispatched. The argument in question is that differential tooth form clearly reflects differential diet among animals today. We can use this to infer diets for extinct species by comparing their teeth with what we know of the dentition and diets in modern animals. This is contrary to the view held by Ken Ham and the AIG PhDs who maintain that all animals were vegetarian prior to the Fall of Adam, including tyrannosaurs. This aspect of natural history has to be true for Ham and fellow creationists in order for them to retain consistency with a specific verse in Genesis. So they argue that the dietary inferences paleontologists and other evolutionists make from teeth cannot be correct. As an example of this, Ham himself has pointed out that tyrannosaur teeth and bear teeth are both “sharp” and yet the bear’s diet is comprised of a significant portion of plant foods; hence there is no real reason to think tyrannosaurs couldn’t have also been vegetarians.

My response was that bear teeth and tyrannosaur teeth are not alike at all, as Ham suggests. (Of course Ham only indicated that both species possessed teeth that were “sharp”, not necessarily similar in morphology. But this is an example of deliberate subterfuge the AIG staff does best: gloss over the specifics and make the necessary generalization to prove your point. There is not doubt that in describing the teeth of tyrannosaurs and bears as “sharp” Ham is expecting that his audience will understand him to mean “the same”). If you are interested in the simple question of why bear teeth are different from tyrannosaur teeth, the observation still remains that tyrannosaurs have teeth much more in common with those of modern carnivores than plant eaters. Again, from this I would have to infer that tyrannosaurs were clearly carnivores. At this point, the only defense Ken Ham can come back with is a line from the bible[1].

However, my reader pointed out some additional issues to consider that at first glance would re-open the case for tooth morphology having anything to do with diet and at least force us to ask if AIG might have a viable alternative. He basically made three points (except for words in quotes I’m paraphrasing):
1) polar bears feed exclusively on other animals, yet their teeth are “hardly different” from other bears;
2) flat teeth are for grinding/chewing and the fact dinosaurs had gizzards would mean that scimitar-toothed species like Tyrannosaurus could have eaten plants, swallowed them whole and let their gizzards do the work;
3) “As for serrations” the pro-sauropod group of dinosaurs, thought to be herbivores, “…had them on their teeth like Tyrannosaurus”.

Certainly the responses to these observations are important, but that is not what prompted me to write this post. What really intrigued me was the process I engaged in while obtaining the information. It is the process of discovery that, as much as the answers, serves to radically distinguish science from creationism in all its forms. As I said, my reader raised several issues that, on face value, would be sufficient for most people to stop and wonder if Ham and AIG weren’t at least raising a legitimate issue. For Ham, AIG, and on a different level, the intelligent design advocates, inquiry would completely cease at this point. See, O’Brien is wrong: polar bear teeth are hardly different from other bear teeth and they exclusively eat meat…hence it is possible that tyrannosaurs ate vegetation at one time. Here, the entire goal is accomplished: raise reasonable doubt with the general populace at large.

But science follows a completely different process. Upon reading the phrase “polar bear teeth are hardly different from other bears” the first thing I did was ask myself, “is that true?” and reach for a book on mammalian anatomy; and I did it so sub-consciously and automatically that the significance of the act did not become apparent until a few hours later. Scientists constantly question whether their data (and others') are correct…it’s ingrained as part of the process. The same cannot be said for creationists.

Turns out, polar bear teeth are not “hardly different” – their back teeth are distinctly more carnassial (for ripping meat, not grinding) than those of their ursid (bear family) cousins. They are not completely like the back teeth of obligate carnivores like wolves, but it also turns out that mostly what they eat is seal fat and they are not entirely carnivorous (although clearly more so than brown or black bears). On the heels of an automatic question when being confronted with a new “observation” also came an automatic mental prediction (also an inherent part of science but not of creationism or intelligent design): IF tooth morphology is largely explained by diet, THEN another species of bear with a radically different diet should also exhibit radically different tooth morphology from other bears. Sure enough, the Panda, which subsists on bamboo, exhibits a much different tooth morphology than seen in other bears.

But the scientific process didn’t stop there. It came along with me as I read through my reader’s list of observations. The gizzard idea was interesting, but do all dinosaurs have gizzards? No, they are suspected in only a few species because of the presence of “gastroliths” or gizzard stones. And again, IF tooth morphology is a good predictor of diet, then I was betting that the only dinosaurs found to have them so far are probably those with teeth expected to be good for chewing vegetation and probably limited to sauropods and not found in carnivorous dinosaurs – sure enough, that’s the case. Finally, I wondered if the “serrated” teeth of pro-sauropods were really like tyrannosaurs. Of course I hadn’t mentioned tyrannosaurs having serrated teeth in my original post, but that’s part of the overall morphology of a tooth and they do have a serrated edge. But “serration” is not equivalent to meat eating, and in fact iguanas, which are mostly vegetarian, also have serrated teeth. Turns out pro-sauropod teeth are also a lot like iguanas, and in addition are very small, unlike the very large carnivorous teeth of tyrannosaur – i.e. much more in line with eating vegetation than meat.

But science is also about “multiple lines of evidence”…so are there other observations about diet that are consistent with the hypothesis that tooth morophology is largely explained by diet? Yes. Many readers of the Creation Museum Carnival pointed out in the comments that tyrannosaur coprolites (fossil feces) don’t contain plant materials – another observation consistent with the hypothesis. Microscopic analysis of early hominid teeth show that Paranthropus, thought to subsist almost exclusively on hard seeds, nuts and roots because of the unique structure of its teeth and skull, actually shows pitting and gouging expected of that kind of diet. And Australopithecus, suspected of having a more omnivorous diet like humans (again, because of their tooth morphology)? Microscopic analysis shows a smooth surface on the tooth as in modern humans.

So where does that put us with regard to evidence consistent with the null hypothesis that tooth morphology is a very good indicator of diet?:

- bear teeth unlike tyrannosaur teeth
- bear teeth showing variation in tooth morphology with diet;
- gizzard stones highly correlated with dinosaur species whose teeth suggest plant eating
- tooth morphology in pro-sauropods consistent with largely vegetarian ignuanas
- microscopic analysis of tooth wear consistent with dietary differences between early hominids Paranthropus and Australopithecus

And evidence that is consistent with the AIG hypothesis that tooth form has nothing to do with diet?
- a line in the bible

I may be off here, but I'm guessing it's a bit early to reject the null hypothesis in favor of helping Ken Ham maintain his belief in a literal meaning of Genesis. There is no reason to think that the diet of tyrannosaurs was vegetarian at any stage of its evolution and Ken Ham’s personal interpretation of that line is clearly in error. I would suggest he look at some alternative explanations of his own…and he can start with those I outlined in my footnote...


[1] I have to digress here a moment: If you believe the bible to be authoritative from the start, then perhaps that’s enough evidence for you and you can dismiss any observational evidence of the real world. And that’s fine…but it isn’t science. However, those who accept creationism never consider other alternatives on this matter themselves (although they expect everyone else to consider theirs): 1) the bible is not divinely inspired at all, but merely a collection of different types of writing form Bronze and Iron Age people who were trying to explain the world around them without reference to the scientific knowledge we have today; 2) the bible is not divinely inspired, but has been rewritten multiple times, other texts of the time lost or purposefully destroyed, and certain texts available at the time specifically selected, all to give the appearance that the bible was divinely inspired; 3) the bible was divinely inspired but never meant to be anything more than allegorical, metaphorical and symbolic in its broader meaning; 4) the bible is divinely inspired but humans are too evolutionary primitive to understand the complex meaning that is really behind its passages; 5) there is a god and he was responsible for creating the world, but how it was done is best captured in one of the hundreds of other creation stories around the world and not in the bible. Of course, although some alternatives have historical and scientific angles to them and can be tested (for example, we know parts of the bible were re-written to appear more consistent with theological statements from historical documents and early biblical texts themselves; there is also good evidence to suggest the bible texts were purposely selected to convey specific theological arguments as if they were prophesized or demonstrated historically), the alternatives listed are largely theological and can be accepted or rejected pretty much solely on the basis of personal preference.

7 comments:

Anonymous said...

I have CnP'd your post to CARM, since it is a violation of that site's rules to post links to weblogs. I hope you don't mind.

fusilier, who came across your site via afarensis at scienceblogs
James 2:24

CFeagans said...

And I took the liberty of nominating the post for the next edition of Open Laboratory if you don't mind.

The reason I gave was the discussion on dentition is informative and as is the discussion on the scientific process of fact-checking and testing claims. I'm sure that there are one or two others of your posts worthy as well... I've been side-tracked lately and not reading/posting as often as I used to.

Christopher O'Brien said...

No problem for either of you...I appreciate spreading the post around the blogosphere a bit...
Carl, good to hear from you...hope all has gone well with school and family. If I may be so bold: I know you like to blog (and are excellent at it!) but my advice is to make graduate school the top priority...plenty of time to blog after that. Again, good to hear from you - I'll be up at Eagle Lake a lot this summer...maybe I can get some more pelican bones for your daughter's collection!

CFeagans said...

LOL! That reminds me, I need to send you a drawing she made for you... I've been terrible about keeping up with things like that lately. Grad school's going to wait until Fall 2008... turns out my adviser gave me some bad advice and there's a Philosophy class that I'll need to finish. She had me take the wrong one. Don't think I wasn't pissed, either.

MarkV said...

I just wanted to say, that while I agree with your full rejection of creationism, be careful when citing certain findings, or you may find your own work rejected. Certainly, pandas teeth are different from bears- but thst's the point- they are NOT bears at all. You may want to fix that...

PsyXe said...

Actually, though pandas were for a long time considered not to be bears but rather to be related to raccoons, I think scientific opinion is swinging round again and they are now considered to be bears after all.
P.S. These people (Ham et al) are an embarrassment to Christianity :/

Anonymous said...

The one thing that never changes is Gods word. Unlike science which changes everytime a scientist opens their mouth. Good luck with the panda bear or is it panda raccoon.