Bacterial motors carefully studied (Introduction)

by David Turell , Thursday, March 31, 2016, 19:10 (3158 days ago) @ dhw


> dhw; His major contribution was to make the concept of common descent so convincing that even many religious folk now accept the theory, as opposed to that of separate creation. The evidence he accumulated for this theory, in the form of basic patterns, remains just as valid today as it was then.-You are correct, as far as that goes as a popularizer. As to methodology, no. 
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> DAVID: Natural selection is a logical tautology. Of course there will be competition between variations, and small variations was his prime theme. Today we are well beyond Darwin in trying to reach answers.
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> dhw: Agreed. My objection is not to your individual criticisms of Darwinism .... It is the explanation of how evolution works - the theory of random mutations and gradualism - which in your view and mine is collapsing. -Agreed.-> 
> DAVID: Epigenetics is now being shown to be a more powerful heritable mechanism than previously thought. Perhaps it will turn out to be so powerful as to create species, but I doubt it. Just thinking of the issues involved in a giraffe neck make me pause. Same seven vertebrae (patterns), tremendous blood pressure, and did the acacia trees start short and as they grew taller the giraffes stretched their necks? Kipling! Not to mention leather-like tongues to handle the thorns that are like daggers.
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> dhw: All the theories so far seem like “just-so” stories if we tell them that way. -Skipped the just-so's which are wonderfully inventive. But the giraffe series shows the usual jumps, nothing in tiny changes:-http://phenomena.nationalgeographic.com/2015/10/07/how-giraffes-became-winners-by-a-neck/-"But even though the earliest giraffes already had slightly-elongated neck bones, there was no “March of Progress” towards towering heights. At least one - and possibly more - giraffe lineages reverted to abbreviated necks hung around stout vertebrae. Giraffokeryx was among the earliest of the short-necked giraffes, browsing low-lying foliage around 12 million years ago, and within the last three million years Sivatherium, Bramatherium, and the okapi followed suit. The short-necks proliferated alongside their lankier relatives, which is why we still have both short- and long-necked giraffes today.
But even though the earliest giraffes already had slightly-elongated neck bones, there was no “March of Progress” towards towering heights. At least one - and possibly more - giraffe lineages reverted to abbreviated necks hung around stout vertebrae. Giraffokeryx was among the earliest of the short-necked giraffes, browsing low-lying foliage around 12 million years ago, and within the last three million years Sivatherium, Bramatherium, and the okapi followed suit. The short-necks proliferated alongside their lankier relatives, which is why we still have both short- and long-necked giraffes today.-"Truly long-necked giraffes didn't evolve until about 7.5 million years ago. Samotherium, Palaeotragus, Bohlinia, the extinct Giraffa sivalensis and the living Giraffa camelopardalis preserve enough transitional features to let Danowitz and colleagues reconstruct how this stretching occurred. It wasn't simply a matter of drawing out their vertebrae as if they were in some sort of anatomical taffy pull. The front half of the neck vertebrae became elongated in Samotherium and Palaeotragus, generating forms intermediate between today's Giraffa and their foreshortened predecessors. Then, within the last two millions years or so, the lineage leading up to the modern Giraffa elongated the back half of their neck vertebrae, giving them even more reach and making them literally at the top of their class."-Comment: No just-so here! Only jumps in phenotype.