Hi [Xeno]Julius
Another take on your interesting question(s) -
If you’re asking whether there is anything intrinsic to the chemistry of DNA which makes some kinds of changes in phenotypes (‘bodies and what they do’) more likely than others, then the answer does seem to be no at the micro level of individual DNA bases. By analogy, there is nothing intrinsic to the alphabet that makes a number of random changes in single letters likely to alter the meaning of a written text in a consistent way.
But it is easy to imagine that some kinds of phenotypic change are easier than others, just because the laws of physics, geometry and materials science work the way they do. D’Arcy (his first name) Thompson wrote a classic book about this in 1917 called ‘On Growth and Form’. It’s perhaps the oldest biology book continuously in print apart from Darwin’s stuff.
A sketch of Thompson’s, showing a simple geometric relation between different species which face different selection pressures:
Center for Imaging Science | Page not found
More recently the work of David Raup has shown that many shapes closely resembling snail shells can be generated with a simple 3-parameter equation. Try it here -
http://members.aol.com/macops/Raup.html
but perhaps that there may be hidden (at least at present) patterns within DNA that allow for interesting and gradual phenotypical progressions even with a random mutative engine.
The interactions of genes during embryogenesis may very well have their own ‘rules of grammar’ that lead to some things being easier than others to ‘say’ with economy and elegance. Such phenotypic changes would be the ones most likely to appear by chance.
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