What drove bird evolution?

lets take a look at some, and see how unique birds are. bats that's one specialized system! wrong, but moving on. anything that gets goosebumps, including us. lots of things, but especially theropodal dinosaurs what? my neighbor's dog. covered that beaked dinosaurs, such as triceratops and protoceratops. turtles. and LOTS of animals eat mouth-only. everything your dog rex to tyrannosaurus rex. what does that mean? alright, let's look at that list again! long fore-arms are better for catching prey. sounds like a function to me. flightless flight feathers have all kinds of uses. warmth, catching insects. gliding. sexual displays. less weight means faster. faster means better at catching prey, and less likely to become it. shorter tails allow more upright posture, which means better at catching insects with the flightless flight feather also sexual displays. like, you know, a peacock. good at shearing stuff. where to start. may i suggest reading some dawkins? functionality changes over time. a little functionality is better than none. no specializations are suddenly developed, but gradual adaptations from pre-existing forms. evolution is not uni-directional. de-evolution is evolution, whether you like it or not. you can't accept one and not the other.that, and we have a fossil record chock-full of half bird, half dinosaurs.

oh. here's another good example of the error in your thinking. we'll use dembsky's 747 even. this should be fun.the specialized components of a modern jet airliner are as follows:

• the jet engine
• the wings
• verticle and horizontal stabilizers with control surfaces
• navigation system
• wheels
• throttle and stick
• etc

is it possible any such airliner exists with more primitive forms of these things? of course. what about the wright brothers' planes? the classic one you see uses an internal combustion engine borrowed from cars (and a poor example of one too), big propellors, and lack of control surfaces (wing-warping used instead), and no stick or throttle at all. the thing the practiced on before powered flight was a glider, and it lacked the engine and props. the wing were made of canvas, and certainly not nearly as functional as the modern wing.it still has the features, just in less functional forms. and it works, barely, but it lead to developement of all modern flight. transitional forms exist even in technology. a jet may be useless until it's complete, but it's based on the designes of ram-jets/rockets and the propellor. not having an control surfaces is bad when your wings are made of metal, but just fine when you can bend them more freely.these systems all developed out of changing need and single advancements in technology. no one sat down and dreamed up the 747 out of thin air, but based it previous designs, and previous inventions. even the wright brothers' did this.

i must say, those image captures were really informative! not.but you're right, in some respect. at one point in the history of the earth, gravity here did in fact change. but only a little. the change was an indirect effect of acquiring more mass. at some point in the very early precambrian, an object the about size of mars collided with earth. we kept most of the mass, but it ejected a portion of the earth's mantle into orbit, forming the moon. we know this because it's the only model that fits all of the data on composition, mass, orbit, and shape of the moon.while gravity may has increased a little, the fact that half the planet turned to liquid or maybe even broke up would have pretty mush killed everything. but not the dinosaurs, who lived a few billion years later.we do however know what killed the dinosaurs. something that blanketted the planet in a thick layer of soot with a very abnormal percentage of iridium, which means it was probably from outer space. this object was significantly smaller than the one that made the moon (a good number of species survived). there's a crater in the yucatan that dates about right, and looks the right size for a 6-mile asteroid, which would be the size neccessary to cause mass extinction in this manner. well, considering that the best fitting model is the one i described above, and there's no concievable mechanism to randomly change the earth's gravity, i'm gonna file this one in "crackpot claims" unless you can show me exactly what caused it, and then explain the k-t boundary.[editted to add:]oh, and btw. documentaries have been known to lie. look at fox's special on the moon landing hoax, and just about anything michael moore makes. This message has been edited by Arachnophilia, 07-15-2004 12:58 AM

sounds like a macroevolutionary change to me.in reality, there's no difference between gaining and loosing features (as they are often correlated). the difference between evo and devo is that evo is a legitimate scientific theory discribing the directionless adaptation of animals and plants (etc), and devo was a one hit wonder new wave band in the 80's.there is no such thing as devolution. only adaptation. hair grows back. i've had lots of bad haircuts.but wait! what good is half a wing anyways? well, that's certainly more useful than no wings in evading predators, isn't it? it's not perfect, and it could be better, but that's teh same case with anything else. for instance, lots of animals have better eyes than we do. but we do just fine."good enough" is fine with evolution, but intelligent design kind of requires perfection, doesn't it? otherwise, it's not very intelligent. whoever said coelosaurs wanted to fly? lots of birds use feathers as sexual displays. that could be one reason the DESCENDENTS of coelosaurs started along that path. over time, this could have taken on other uses. catching insects. gliding. and eventually flight. it's gradual adaptation and change, not just of the systems, but of the purposes of those systems. given 100 million years, less than a quarter of an inch a generation goes a long way. especially if the characteristic that's being selected is used for attracting mates.

ouy of curiosity, what bird lacks a beak? i wasn't especially aware of any, but i'm not really into ornithology.This message has been edited by Arachnophilia, 07-15-2004 01:11 AM

really? prove it then.be careful not to disprove giraffes while you're at it.science, used poorly and misunderstood, can be used to "prove" all kind of silly things. did you know it was once proved that bumblebees were incapable of flight? even though it's plainly observable to everytone that they can, indeed, fly? it came from a poor understanding aerodynamics, without actual study of the wing function.but, perhaps, i know what you're talking about. it was common belief a long time ago that sauropods lived in water, to help support their weight. bracchiosaurus was the example used. they talked about the nostrils on top of its head being used a snorkel.in any case, that was simply disproved about a hundred years ago.

i wasn't even going to bother with that, because it gets debated so often. (and i'd be more willing to call it a dinosaur than a bird, since it lacks several important bird features)i thought you meant modern birds, and i was just stupid.

you have a picture of an ica stone on the top of your page. look for the thread on those here... they're known forgeries.you also have a link to the hava supai pictograph, which looks nothing like any dinosaur that ever lived, but vaguely like an 19th century mangling of an iguanodon skeleton. (all hadrosaurs are quadrapedal. to stand upright, they'd have to break about 4 vertbrae in the lower tail.)but this bring up an interesting point. from the bones you say that grabity must have been less. well, if this was the case, all other animals present at the time would be subject to same forces. humans would be a lot bigger on average if they lived at the same time.so pick one. either dinosaurs lived with humans, or gravity was less. one crackpot theory at a time.

exactly.

they were apparently quite a hit with the tourists, and ica stones became a very profitable business. they don't appear ancient. the carvings aren't worn at all, and the surface of the rocks aren't chipped at all. they also contain dated -- not accurate -- depictions of dinosaurs that never lived in the area. triceratops, for instance, was a popular dinosaur in magazines, but never lived in south america.

well, it doesn't look like a sauropod to me. they didn't stand that way, heads raised and dragging tails. they balanced head and neck against the tail, and both remained more or less straight out from the body.in other words, whoever drew it didn't see a dinosaur, but saw a 19th century misrepresentation of one.

they're out to get your money. as i believe someone pointed out, there is no such dinosaur. the brontosaurus was an apatasaurus who's head somehow got changed with that of a camarasaurus.so, let's begin the lecture on dinosaur physiology, shall we? it's not so much bone structure as balance. but either way, no dinosaur dragged its tail, as depicted in the petroglyph. tails, in the dinosaur world, were used as counter weights, to balance the animal. the depictions of dinosaurs with their tails on the ground are very dated, and the simple fact that image seems to show a dinosaur with its tail on the ground (below ground?) indicates that if a person made it, they hadn't seen a real sauropod at any point. hearts. plural. they think brachiosaurus had about 8 of them, and all pretty large. this was an animal adapted to reaching the highest branches. and either way, the blood pressure study has been done, and it's not problem. that's what tails are for. they counter balance. it's also one reason sauropods have small heads (the other reason may be found above, if you think about it). sauropods that hold their heads outward tend to have high dorsal vertbrae, where thick muscle (and even tendons and bone) attach to make a sauropod essentially a miniature golden gate bridge.but, i guess the millions of foot pounds of torque on that rule that out in today's gravity too. maybe gravity is different in california?

i believe you already have a thread for this, but let's look at a better resolution picture of a REAL seismosaur skeleton. how high would say those dorsal spins are? 4 feet? 5?here's an illustration of its internal organs, but you can see what the skeleton looks like betterit doesn't need to hold up a lot of weight with its neck. just the mass of its head and neck. notice how the vertbrae just fore of the hips are turned? i don't know exactly where you're getting your figures, but the neck itself doesn't actually matter. the neck is counter balanced against the tail, so that the net force downward is over the hip. the way the bones are deforemed near the hip is evidence of that. edited to fix page width - The QueenThis message has been edited by AdminAsgara, 07-18-2004 01:29 AM

you just haven't done your reading. here's a hint, get off the internet. i remember very distinctly when the issue of the cardiopulmonary system of a brachiosaurus was dealt with. i do believe they even had fossil evidence to support it.and no, you wouldn't be aware of any creatures today with more than one heart. not many creatures are specifically evolved to grow so high.

i think you don't understand gravity. suspension bridges work just fine, and sauropods are built like moving suspension bridges. they don't even have to hold up that much wieght.