sethg@athena.mit.edu (Seth Gordon) (09/07/88)
[Followup to talk.origins; I hope Eric can find his way over there to continue this discussion. I cross-posted to sci.bio because I've never seen this anatomical question before, and perhaps the biologists would deign to respond to a creationist "argument" more original than "It violates the Second Law of Thermodynamics". Onward!] >In article <sX8-1uy00XoDM4lVY-@andrew.cmu.edu>, ee0n+@andrew.cmu.edu (Eric James Ewanco) writes: >> I was in the dentist's office getting my retainers adjusted and the doctor >> innocently enough said something that intrigued me. I asked why there are >> ridges on the bottom of the top retainer. He said that our palates have >> ridges, and the function they perform is to prevent you from spitting so >> much when you talk, and so they had to be duplicated in the retainers. >> Maybe there were once people with differently designed palates, and those >> with the non-spitting palates (our ancestors) became enraged by those that >> spat when they talked and decided to kill all the humans who spat when they >> talked so that there would only be people with non-spitting palates left to >> reproduce. Interesting, huh? This might make some sense if humans were the only animals with ridges on their upper palates, but I've seen/felt them on cats and dogs as well, so I suspect they're common to all mammals. I propose a much simpler explanation: In forming the mouth, the embryo creates too many cells for the upper palate's cartilage (after all, better too many than too few, right?), and compensates for the excess by wrinkling the sheet of cartilage, the same way your skin wrinkles when you get old or you get out of the bath. I'm not sure if we need to bring spit into the explanation at all. An animal that spits a lot while talking would, by definition, lay saliva all over the place, leaving a trail that predators can smell. If the proto-mammals (the therapsids, right?) made lots of noise, they could have evolved this spitproof palate, and their descendants -- modern mammals -- would have inherited it no matter how little it helped them. If the proto-mammals were quiet types, perhaps the ridges simply evolved as "insurance" against having holes in the roof of one's mouth. Or maybe it goes even farther back. Do reptiles have spitproof palates? (Disclaimer: I am not a paleontologist, anatomist, or embryologist, and thus all of the above scenarios are based on the wildest conjecture. Children, don't do this at home -- you could get hurt.) -- "Men, if we lose this [soccer game], we'll be the shame of the civilised world ... *and* America!" --- _The Goon Show_ -- bloom-beacon!athena.mit.edu!sethg / standard disclaimer