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Author Topic:   Theropods and Birds showing a change in kinds
Peepul
Member (Idle past 5018 days)
Posts: 206
Joined: 03-13-2009


Message 14 of 150 (542058)
01-07-2010 12:18 PM
Reply to: Message 3 by slevesque
01-07-2010 9:36 AM


quote:
Similarity, either in the phenotype or the genotype, does not prove relationship unfortunately.
.
Though it's one of the many strands of evidence that do, collectively, prove exactly that.
Some of the genotypic similarities are in themselves strong evidence of relationship - particularly elements that are non-functional such as ERVs, LINES, and pseudogenes.
Likewise similarities in genotype between creatures with strongly different phenotypes is very good evidence of relationship - when supported by fossils that show intermediates between them.
In the theropod / bird case, we don't have access to genetic data about theropods, but we do for birds, and they show the existence of pseudogenes, for example, for teeth. Here's info on some research on a mutant chicken with teeth.
Surprise: Chickens Can Grow Teeth | Live Science
We also have a wide variety of intermediates between the birds of today and their ancestors, most discovered quite recently. It's clear that feathers evolved first, in flightless dinosaurs, and were then co-opted for flight. There are intermediate feather types in the fossil record which have a simpler structure then feathers now.
Here's a nice link on feather evolution.
Feather evolution
This link makes clear that feathers are unlikely to have evolved from scales - so I think you're right about that (although this article is not primary literature).
Edited by Peepul, : mis-spelling of theropod

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Peepul
Member (Idle past 5018 days)
Posts: 206
Joined: 03-13-2009


Message 15 of 150 (542060)
01-07-2010 12:39 PM
Reply to: Message 10 by slevesque
01-07-2010 10:53 AM


quote:
I'm not saying there are no other evidence as you have said.
What I'm saying is that CS has given only this evidence, and declared it to be sufficient to convince him of relationship.
I think that's fair comment Slevesque - but what do you think of the other evidence?

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Peepul
Member (Idle past 5018 days)
Posts: 206
Joined: 03-13-2009


Message 65 of 150 (545343)
02-03-2010 8:35 AM
Reply to: Message 57 by slevesque
02-01-2010 3:43 PM


quote:
You ask what ese is needed. For similarities to be conclusive proof of common descent, you need to be able to prove that all other options aren't possible.
Slevesque, we do not need to go down that road. What we do is look at multiple strands of independent evidence pointing to common descent, not just physical similarity. When multiple stands suggest the same conclusion, we can accept we have probably found the right answer.
AbE - Slevesque, having read one of your latest posts, I think you'll agree with me!
To me whether any one strand is sufficient on its own is a non-question.
Edited by Peepul, : No reason given.

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