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> Furthermore, the idea that complex parts like a brain and nervous system—including nerve cells, synapses, and neurotransmitter molecules—could evolve separate

> Furthermore, the idea that complex parts like a brain and nervous system—including nerve cells, synapses, and neurotransmitter molecules—could evolve separately multiple times perplexes evolutionary biologists This makes absolutely no sense. Why would this be perplexing? If evolutionary pressure causes a feature to evolve once in one part of the tree of life, why couldn't it happen multiple times independently? It would be a lot more surprising if it didn't!

pbhjpbhj 12y ago
>If evolutionary pressure causes a feature to evolve once in one part of the tree of life, why couldn't it happen multiple times independently? // Isn't it rather that the features work in the same way. Bats and dolphins [1] using echolocation that - I've heard - works the same way but the pressures on them are different, the environments different. Given the random occurrence of mutations it seems striking (to me) that these similar paths should be followed. A corollary would appear to be also that if parallel evolution can converge on identical structures that reliance on morphological features to indicate common ancestry is flawed. If evolution tends to converge then a geological sample with a simple form of fossil can't be assumed to be contemporaneous with another sample, the fossils could be the result of parallel evolution. I've never understood why mainstream paleo-biology seems to reject that life could have started in more than one place. Convergent evolution suggests that the same types of complex structures can develop independently too. Perhaps Star Trek's universe of four-limbed, bipedal, binocular aliens isn't so far-fetched after all!?! --- [1] http://www.nature.com/nature/journal/v502/n7470/full/nature12511.html http://www.nature.com/nature/journal/v502/n7470/full/nature1...
andrewflnr 12y ago
We could expect some sort of electro-chemical processing network to evolve multiple times. It's crazy to suggest they would all have the same structures and use the same neurotransmitters, to have all the details be the same. I'm not really familiar with the nervous systems of comb jellies, but I'm guessing the latter case is what they're looking at.

pbhjpbhj 12y ago

>If evolutionary pressure causes a feature to evolve once in one part of the tree of life, why couldn't it happen multiple times independently? // Isn't it rather that the features work in the same way. Bats and dolphins [1] using echolocation that - I've heard - works the same way but the pressures on them are different, the environments different. Given the random occurrence of mutations it seems striking (to me) that these similar paths should be followed. A corollary would appear to be also that if parallel evolution can converge on identical structures that reliance on morphological features to indicate common ancestry is flawed. If evolution tends to converge then a geological sample with a simple form of fossil can't be assumed to be contemporaneous with another sample, the fossils could be the result of parallel evolution. I've never understood why mainstream paleo-biology seems to reject that life could have started in more than one place. Convergent evolution suggests that the same types of complex structures can develop independently too. Perhaps Star Trek's universe of four-limbed, bipedal, binocular aliens isn't so far-fetched after all!?! --- [1] http://www.nature.com/nature/journal/v502/n7470/full/nature12511.html http://www.nature.com/nature/journal/v502/n7470/full/nature1...

andrewflnr 12y ago

We could expect some sort of electro-chemical processing network to evolve multiple times. It's crazy to suggest they would all have the same structures and use the same neurotransmitters, to have all the details be the same. I'm not really familiar with the nervous systems of comb jellies, but I'm guessing the latter case is what they're looking at.