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Post by James Hannam on Feb 16, 2009 12:01:51 GMT
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Post by humphreyclarke on Feb 16, 2009 12:47:14 GMT
I am Robert Boyle on that thread. My comment on the birds issue was: I think he must be referring to the Dromaeosauridae which was a family of bird-like theropod dinosaurs. They share many features with the class Aves. Birds and dromaeosaurs are closely related but dromaesaurs are not ancestral to birds. So flight feathers either evolved twice, once in dromaeosaurs and once in birds, or just once, in a common ancestor of both dromaeosaus and birds.As for the other 2 examples of convergence, I have no idea.
en.wikipedia.org/wiki/Dromaeosaur#Relationship_with_birdsDawkins has commented along similar lines (see my post) so I think I was on the right track. I must admit, I got a bit frustrated with the Guardian commentators when I said. You guys got any specific criticisms to make?, or are just going to continue recommending each others anti-theist catchphrases and revelling in your own intellectual brilliance?. |
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Post by James Hannam on Feb 16, 2009 13:03:34 GMT
Humphrey, Brilliant blog post. Thank you for writing that up. Fascinating stuff. I've no idea where I stand on converging, but your post has really helped me understand the issues. Best wishes James |
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Post by humphreyclarke on Feb 16, 2009 13:34:29 GMT
Thanks James
On the eye issue, it looks as if certain parts of the eye have a common ancestry. the best example is the visual pigments. However from this common ancestor complex, image-forming eyes have evolved multiple times using many of the same proteins and genetic toolkits in their construction. The fact they used the same basic toolkits - which are put to use when exposed to the right selective pressures or environmental stimuli - probably explains a lot of the similarities. The gene which controls where your eyes ends up is PAX6 which controls where the eye develops in organisms ranging from mice to humans to fruit flies. if you are looking for human specialness, don't look at the genome.
Convergent evolution is a scientific observation and it is not immediately apparent what it has to do with religion. What you can say, looking at it in detail, is that there appears to be a deeper structure of life and a coherence in how it is structured and organised. Evolution on this planet is simply the end point of a process of cosmic evolution in which star and galaxy formation occurs around black holes and the ingredients or life are scattered across the universe. The physics and chemistry have to be finely tuned for this to occur, and you can begin to see a concordance with that in biology once we move past this idea that life's history is all a complete mess.
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Post by humphreyclarke on Feb 16, 2009 14:08:04 GMT
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Post by humphreyclarke on Feb 16, 2009 16:20:29 GMT
I've now revised my post on convergence (it was a bit rushed).
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Post by sandwiches on Mar 1, 2009 22:22:12 GMT
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Post by humphreyclarke on Mar 2, 2009 10:27:13 GMT
I suspect it will be a mixture, some would have been able to travel between poles when the climatic conditions were different. There will probably be examples of convergence, for the simple reason that the organisms face similar environmental challenges, to which there will only be a finite range of solutions. It underlines the power of nature that such a hostile environment can be host to such an astonishing range of species. Life is remarkably resilient and that bodes well for its prospects elsewhere in the universe.
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Post by humphreyclarke on Mar 2, 2009 14:52:41 GMT
As an addendum to this, apparently the current issue of Nature has a series of articles on evolution. The introduction is interesting because it says that the current understanding of evolutionary biology suggests that evolution is not as stochastic as people like Steven Jay Gould thought.
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