markfiend

I've been having a discussion with a YEC, and he has made the assertion that "fossils are just bones, and you can't tell a lot from bones." Now I know that this isn't true, (and there are plenty of fossils that are more than just bones) but I was wondering just how much it is possible to tell about an animal from its bones?

Examples:
Rhinoceros "horns" are made from compacted hair (like a dreadlock on the nose ), so if we didn't have living rhinoceroses, would it be possible to tell from their skeletal remains that they had horns?

Elephant trunks have no bones, same question.

By analogy is it then possible that extinct animals may have had non-skeletal features that we'll never know about unless we find them with soft tissues also preserved? I'm thinking of things like sauropods with trunks, T. rex with feathers, etc.

Oolon Colluphid

That’s right. They’re stone. But yoou can tell rather a lot from stones...
There’s plenty, but they are inevitably rare. You can get occasional imprints of body outlines, feathers, impressions of hide, and so on. And of course there’s tracks and footprints, coprolites (fossil poo) etc.
Heaps. Bones don’t just float around inside a body; they have ligament and muscle attachments, for instance, and where these attach there are distinctive shapes and surfaces. A carnivore’s saggital crest, say, could be a decoration... but its surface will show that it was actually where large jaw muscles attached. This is why palaeontologists have to be great anatomists. The whole point is to figure out how it all fits together into a living organism. So you need to work out how the bones were overlaid by other tissues... and for that, anatomy is essential.

Best analogy I can think of: you know the way forensic artists can reconstruct a person’s face from just the skull? Those clay models? Skull... then these muscles go across like this, and these ones go round here... and voila! Obviously it’s easier for humans (or any other living thing), cos we know precisely what muscles and where they go. But the same principle applies. (Actually, it’s no analogy, that’s exactly how it works.)
Don’t know for sure, but the horn is a hefty thing, which will pull on the skin of the snout and hence on where the skin attaches. So off the top of my head, I suspect it’s perfectly possible to spot that it had something on its nose.
Nope, no bones... but a bloody great hole at the front of the face surrounded by muscle attachment surfaces suggests something was there.
Yep, perfectly possible.
Again, there would be skeletal indications of that sort of thing.
Quite plausible.

Cheers, Oolon

markfiend

Thanks Oolon, do you mind if I quote your reply in full to my YEC friend? He has refused to come here to look for himself; calling the place "Internet Infidels" has put him off for some reason!

Oolon Colluphid

Quote away, old chap! But I'd be inclined to wait till there's more responses in: my above reply is just educated guesswork, and what you really need is an anatomist or palaeontologist. (Per Ahlberg is an Infidel member, and he'd do nicely, but I expect he's off doing real work!) When this thread's 'done', you could give him a link just to this page.

I'll have a look in Benton's Vertebrate Palaeontology and Aiello & Dean's Human Evolutionary Anatomy tonight and let you know any more I can find out -- I'm sure they have stuff on reconstructing the organism from the fossils.

I'd urge you to try and get your creationist to come here, though. If by some strange chance he's actually interested in finding out about anything evolutionary, he could ask his questions to the board. I've never seen the point -- and you could quote me on this -- of one-to-one discussions of this stuff. If you don't know an answer, it suggests that it isn't known, whereas all it actually shows is individual fallibility. That's the joy of these threads: there's usually someone around that does know about it!

I suppose it depends on your YEC's purpose in discussing. If he just wants to score points over you, then one-to-one is fine. If he wants to know whether he's actually right or not, he needs to ask around.

But if he won't come, feel free to field his questions here first. No matter how much you know about a subject, there's always others who can add useful details.

Cheers, Oolon

Ergaster

Tell your friend to do a google search on "forensic anthropology" if he thinks that bones can't tell you much. One of the reasons I ended up doing paleoanthropology at school was because I saw some tv documentaries on Clyde Snow and others who reconstruct lives from skeletal material, and I was astonished at just how much you *can* tell from bones, with the right training (my other big interest, after human evolution, is paleopathology--determination of disease and trauma from the skeleton. That is an *enormous* field in human biology. I think Dr GH might have something to say about that).

Secular Pinoy

I myself am quite interested in taphonomy after seeing a documentary called Raising the Mammoth (I think).

Dr.GH

Fossils are much more than "just bones." As Oolon has pointed out there are many kinds of fossils. The most ancient evidence of life on earth are the iron minerals secreted by bacteria 3.5 billion years ago. Indeed there is a great deal that one can determine from "just" bones.

First, some web sites:

Forensic Anthropology (I like these 'cus they mention me. What an ego!)
http://medstat.med.utah.edu/kw/osteo/index2.html

http://www.soton.ac.uk/~babao/links.htm

Taphonomy
http://paleo.cortland.edu/tutorial/T.../taphonomy.htm



The forensic pages will give you (and your friend) an idea about how much one can actually learn from a bit of bone. But the taphonomy pages are even more useful as they should make it clear that one does not merely start out with just a bit of bone.

First, there is the matrix (sands, muds, or lithified sand and mud) that the fossil is recovered from. From the rock itself we learn a good deal. For example the sediment from a lake is different from that in a saltwater bay, the channel of a river is different from the infill of a marine trench. The sediment of the deep basin of a lake is different from the lake margin sediment. And so on ... So when we find our bone we also know what sort of environment it was deposited in, and often this is where the animal lived. A carcass can be a complex environment, just as a body is. Microfossils such as pollens, phytoliths, and sometimes even parasitic arthropods can be recovered along with "just" bones.

From the teeth, coprolites, stomach contents, and occasionally the chemical composition of the bone, we can determine diet. Teeth not only have shapes that are patterned, but they show wear that is characteristic of certain diets. For example, plants have microscopic silicon structures called phytoliths particularly in the leaf and bark. These will leave microscopic scratches on the enamel of teeth. If you find the scratches, the animal ate those parts of plants, no scratches and you now know that the animal did not.

Have fun.