In the
Re-Theory of Evolution thread, Bluejay and Bertvan have been discussing whether genetic changes precede or follow phenotypic changes.
Bertvan stated that ...
Bertvan writes:
My own view is that the ability to make intelligent, purposeful responses is an observable trait of all living systems. Even single cells are capable of some limited creative response to environmental stimuli. Such responses are heritable, epigenetically, as traits develop, and only become encoded into the genome if persistent over generations
The last part of this sounds quite like a real phenomenon, that of genetic assimilation. Genetic assimilation involves environmental effects giving rise to particular phenotypes which can then become genetically 'fixed' as it were so the environmental stimulus is no longer required.
The problem is that there is no evidence this is in any way connected to any 'creative response'. Phenotypic responses to the environment are still mediated by the interaction of the organisms genome with its environment. There is nowhere else for the 'responses' Bertvan posits to come from.
There is certainly no evidence that such 'responses' are purposeful or guided by any form of intelligence.
Bluejay countered ...
Bluejay writes:
be careful with this, because phenotypic changes don't usually happen without genotypic changes happening first.
There is certainly plenty of empirical evidence from hundreds of mutational studies to support this, although it does not perhaps give the neccessary credence to the idea that instances where phenotypic change has preceded genotypic change (in some sense at least) may still have considerable significance.
These arguments raise these questions to my mind ...
Is there a coherent argument to be made for any sort of entirely genetically independent epigenetic inheritance becoming genetically encoded over generations?
Is there any reason to suppose that such a mechanism would in any way require intelligence to operate?
Is too much emphasis put on purely genetic changes and not on the long term interactions between the genotype and the environment?
TTFN,
WK
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