Human organ evolution (Introduction)

by David Turell @, Saturday, April 21, 2018, 15:19 (425 days ago) @ dhw

DAVID: Deep divers have big spleens:

DAVID’s comment: This is an organ adaptation, not a change in the human species.

dhw: Yes indeed, but it confirms a pattern which runs through so many of these threads. Adaptation to the environment causes changes to the body, but we don’t know the extent to which the body can change itself. The divers didn’t tell their spleens to get bigger. Of course it may be that natural selection caused bigger spleens to outlive smaller spleens, but an alternative would be the process already observed elsewhere, i.e. that concentrated usage results in expansion of the organs used. With musicians and taxi drivers it’s parts of the brain, and with the divers it’s the spleen. One can envisage the same process occurring when land animals entered the water, and limbs became fins, or vice versa, with fish evolving legs out of fins. Not proven, of course, but there is a satisfying consistency in this hypothesis, and it still allows for your God as the inventor of the mechanism that makes it all possible.

It is possible that the explanation lies with the first that dived. Those with larger spleens were more productive and produced more divers. The process repeated over and over made the folks we have today. Pure Darwin which makes sense in this case. I see no parallel in those mammals that took to water. That has to be saltation.

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