Although my knowledge of embryonic development is quite poor, this type of question has always struck me as a very weak one:
quote:
2) Kalinka et al. (2010) have documented that the developmental hourglass model (which describes the observation that embryogenesis within a phylum diverges most extensively during early and late development, while converging in the middle) holds true even with respect to patterns of gene expression, which has a central role in elaboration of different animal forms. Given that mutations affecting the earliest stages of development are the least likely to be evolutionarily tolerated, would you please explain how you would account for this observation in terms of evolutionary rationale?
If they are not well tolerated, then how is it that these mutations DO EXIST in very healthy species? It would seem to me that they refute themselves on this one. It reminds me of the creationist who argued that according to the 2LoT there had to be a massive input of energy into the Earth in order for evolution to occur, all the while ignoring a rather obvious and massive nuclear furnace in the sky.
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