More of Saber-Toothed Mammals

5 04 2007

I really wish I still had the video, but as a child I distinctly remember seeing a stop-motion animation documentary featuring extinct North American mammals. The most memorable scene (if for no other reason than it’s the only one I remember) involved a Smilodon jumping onto the back of a Megatherium, attempting to bring down the beast. Ultimately, the extinct cat fails, the narrator going on to explain that the saber-toothed “tigers” went extinct because their tooth grew so large as to prevent their mouths from closing properly, and they simply could no longer eat. This child-oriented documentary was aired in the early 90′s, and yet scientists knew this idea was hopelessly wrong decades before! Here’s a passage from G.G. Simpson’s The Meaning of Evolution (3rd ed., 1950);

The sabertooth is one of the most famous of animals just because it is often innocently suppossed to be an indisputable example of an inadaptive trend. In fields far remote from paleontology the poor sabertooth has some to figure as a horrible example, a pathetic case history of evolution gone wrong. Its supposed evidence is thus characteristically summarized in a book on (human) personality: “The long canine tooth of the saber-toothed tiger grew more and more into an impossible occlusion. Finally, it was so long that the tiger could not bite effectively, and the animal became extinct.” Now, like so many things that everyone seems to know, this is not true… Throughout their history the size of sabertooth canines varied considerably from one group to another but varied about a fairly constant average size, which is exactly what would be expected if the size were adaptive at all times and there were no secular trend in adaptive advantage but only local and temporary differences in its details. The biting mechanism in the last sabertooths was still perfectly effective, no less and probably no more so than in the Oligocene. To characterize a finally ineffective a mechanism that persisted without essential change in a group abundant and obviously highly successful for some 40,000,000 years seems quaintly illogical! In short, the “inadaptive trend” of the sabertooth is a mere fairy tale, or more fairly, it was an error based on too facile conclusion from imperfect information and it has since been perpetuated as a scientific legend.

While there were some differences in the characteristics of saber-toothed cat canines (length, thickness, etc.), the central point of what Simpson writes is true; the idea that these cats kept evolving longer and longer teeth “just because” is utter nonsense, but yet because it appeared in so many popular works, it became accepted mythology. It is also important to note that things have changed since Simpson initially wrote this piece, being that on the next page he gives a comparison between a skull of Eusmilus and Smilodon to show that comparative tooth-size of these mammals was essentially the same at the beginning and the end. What we now understand, however, is that Eusmilus was a Nimravid and belonged to the family Nimravidae which are considered to have evolved a parallel body form to the true saber-tooths like Smilodon. While this does put a dent in Simpsons comparison between the two skulls, the central point still holds true; an earlier carnivore had canines similar in size to a much later one, neither skull giving us any reason to think the teeth prevented these animals from feeding.

This particular point in the book also illuminates a general theme of Simpsons book; the search for general trends in evolutionary change, if they even exist to begin with. While such ideas may be unheard of today, Simpsons gives considerable space to debunking orthogenesis and autogenic concepts of evolution, the beliefs that evolution always proceeds in a straight line and that there’s some kind internal driving force in organisms that makes them evolve, respectively. While there may still be some ancient adherents to these ideas, it is interesting to note how seriously they are discussed and refuted in a book little more than half a century old. Just as well, in reading Evolution’s Workshop I was surprised to find such a diversity of evolutionary ideas that were designed to somehow debase Darwin’s brand of evolution, i.e. the mixed catastrophism/evolution/secular creationism of Louis Agassiz. Evolutionary thought has itself evolved at frighteningly fast pace, and I think it’s as important to know the history of this brand of science as it is to keep up with the latest phylogenetic studies or fossil discoveries. Sometimes I even wonder about what books 50 years from now will say about this time in history pertaining to evolutionary science; what will the 20/20 hindsight of history reveal?

About these ads

Actions

Information

5 responses

5 04 2007
Laelaps

[...] More of Saber-Toothed Mammals [...]

21 05 2007
Laelaps

[...] fangs?Video: Juvenile Leopard cares for baby baboon?AiG, unfossilized bones, and the lies thereinMore of Saber-Toothed MammalsCountering Creationism, Pt. II; “Zinj”Some monsters are realPhoto of the Day: African Wild [...]

5 10 2007
Why do I bother? « Laelaps

[...] To sum things up a bit, I feel that current paleo-programming all-too-often cheats the audience by hiding the science (or even distorting it), making it appear that all the problems have been solved and we now know everything about these animals. Documentaries that are supposed to be educational are more like B-grade monster movies, only they’re not nearly as fun to watch. As discussed in the comments of The Ethical Palaeontologist as well, many spectacular paleontological finds that are being published in Nature or Science seem to be little more than brief announcements, and it can only be hoped that the specimens will be more fully studied and described (as is the case with the strange theropod Majungatholus from a few years back). Perhaps I could use these problems as a way to launch into the whole “framing” issue, but I think I’ll leave that sleeping canid lie for the moment, although misrepresentation or oversimplification of paleontology to the public is nothing new. [...]

16 02 2008
ray lawson II

I was watching the documentary where they were saying that the sabers could take down mammoths and other creatures much larger than they are, but they kept saying the sabers attacked (mouth open) and they couldn’t figure out why the sabers teeth were so easy to break in a sideways motion.
they got it all wrong, they talked about the apparent weakness of the lower jaw,that they got right, heres my theroy.
The sabers hunt in a pack , and take down prey as a pack (similar to loins in presant day), but(go with me on this) as they throw their massive weight against the bodies of their prey , wouldn’t it make more sense to “hook” the prey with their lower jaw closed, leaving only a couple of inches of tusks to do the damage, inflicting bleeding wounds that would slow the animal down, and eventually lead to its downfall.
the documentary talked about the thickness of the hides of the prey animals the sabers usually attacked as being a couple of inches thick , and they couldn’t figure out how the sabers teeth wouldn’t break if they hit bone as they attacked.
just picture a pack of attacking sabers , taking down a mammoth, spread-eagled around the flanks of the prey, latched on with those huge claws, and mouth closed , tusks, hooked in the preys hide, just using the tips of the tusks that stick out just below the bottom of the jaw, this to me makes more sense, because wouldn’t the bottom jaw act as a reinforcing agent to the sideways impacts that the documentary say would snap off the teeth?
the sabers have large nasal areas to help with the rapid breathing during the “battle” so they could still get the oxygen they need during the exertion of the attack, and if the prey managed to shake off its attackers and get away it would have been tracked down anyway as it would have left a blood trail behind it .
please tell me what you think, and thanks for reading this, it was just “irritating to watch the documentary as they asked all these questions , and the answer was right there.

15 05 2012
science stage

A slave has but one master; the ambitious man has as many masters as there are persons whose aid may contribute to the advancement of his fortune….

After a spirit of discernment the next rarest things in the world are diamonds and pearls….

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s




Follow

Get every new post delivered to your Inbox.

%d bloggers like this: