5X5 Episode 17

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5X5 Episode 17
T-Rex proteins closely related to chickens
27th April 2008 Transcript Verified
5X5 16	5X5 18
Skeptical Rogues
S: Steven Novella
R: Rebecca Watson
B: Bob Novella
J: Jay Novella
E: Evan Bernstein
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T-Rex proteins closely related to chickens

Voice-over: You're listening to the Skeptics' Guide 5x5, five minutes with five skeptics, with Steve, Jay, Rebecca, Bob and Evan.

S: This is the SGU 5x5 and our topic for tonight is: Comparing the connective tissue proteins of T. rex fossils and modern birds such as chickens. A biologist at Harvard University, Chris Organ, has evaluated fossilized connective tissue, specifically collagen, which is a type of protein that makes up most of our connective tissue, that was recovered from the fossil of a T. rex. This is a very rare find where the fossil is preserved well enough that there are still some proteins that they can analyze. They compared the proteins to other living reptiles as well as birds, such as chickens, and they found that the T. rex is more closely related to a chicken than to living reptiles.

E: So, Steve, is it a matter of that we kinda knew this before this protein was discovered but the protein now kinda puts the nail in the coffin on this and seals it up?

S: Yeah, you can also look at it as different lines of evidence are lining up. So, the fossil evidence points to birds evolving from dinosaurs, specifically the theropod dinosaurs, the bird-like dinosaurs, ones that walked on two legs like velociraptor, for example. There's actually a little bit of a question as to whether or not T. rex fits within the subset of dinosaurs that are theropods or if it's related to another branch, but I don't think it matters for the purposes of this analysis. What this means is that dinosaurs, all dinosaurs are more closely related to birds because birds are basically descended from dinosaurs, than they are to other living reptiles. Which makes sense, if you think about the way the branch - the branching tree would go, birds would be closer to dinosaurs than dinosaurs would be to other living reptiles.

R: And now don't anybody get confused, we still do believe that a monkey can kick a bird's butt-

E: Right.

R: -any day of the week.

S: You think so?

R: Yeah, I think so. It just means that some distant cousins of birds might have, at one time, been able to kick a monkey's butt.

J: Steve, and there's no protein - real protein left, though, correct? There's no DNA?

S: Well, DNA is not protein. Right, so, DNA is the genetic code, deoxyribonucleic acid. There's no DNA recovered from this fossil and right now scientists believe that DNA could not survive for 65 million years for - unfortunately for 'Jurassic Park' type of scenarios. There's probably no dinosaur DNA that is viable, that hasn't broken down. It probably breaks down within a million years or two, so we're never going to find it for - for dinosaurs.

B: But the whole chicken, though, I don't think there's much relevance to the chicken, because - isn't it true that the most recent common ancestor of birds was after the Tyrannosaurs - the Tyrannosaur group and the proto-bird group split. Therefore every bird - isn't every bird equally closely related to the Tyrannosaurus?

S: Yeah.

B: So, isn't the chicken just - so it's every bird, it's not just the chicken, it's-

R: Well they did-

S: Yeah, there's nothing special about the chicken-

R: -they did specifically-

B: -well then ok-

R: -say that they compared it, the collagen from the T. rex to the collagen of the chicken, right? I think that's why-

S: Yeah, but you're right Bob they could have-

R: -the chicken is given.

S: -and they also mentioned an ostrich-

R: Yeah.

S: -I think, just to get two - two diverse birds, but yeah-

B: Right.

S: -all birds-

B: All birds.

S: -will - and I also suspect all birds are probably more closely related to all dinosaurs-

B: Right.

S: -than to other reptiles, although, probably mainly the theropod dinosaurs, which is the branch that we think that the birds evolved from. They also used a similar technique to compare mastodons and elephants and they confirmed that they are indeed closely related. Now mastodons-

B: Duh.

S: -died out only thousands of years ago, so it's actually quite possible that we could recover some viable DNA and actually reconstitute the mastodon, or the wooly mammoth.

R: That's not quite as scary.

S: Yeah, but it's cool, though. I'd love to see one of those; that could happen, theoretically in our lifetime.

J: Steve, where did they find the fossil?

S: The fossil was found by John Horner, who is a pretty famous dinosaur hunter, in a fossil-rich stretch of land that spans Wyoming and Montana.

J: Oh boy, I hope they - they find a lot more there.

S: Yeah, it would be great, although, again, the preservation good enough to - to recover soft tissue is extremely rare. So, very very cool, but it still won't lead to 'Jurassic Park' with T. rexes walking around, unfortunately.

S: SGU 5x5 is a companion podcast to the Skeptics' Guide to the Universe, a weekly science podcast brought to you by the New England Skeptical Society in association with skepchick.org. For more information on this and other episodes, visit our website at www.theskepticsguide.org. Music is provided by Jake Wilson.