[ExI] evolution

[John Clark]

On Tue, Jan 28, 2020 at 10:10 AM William Flynn Wallace via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> There are several on this list who know much more than I do about
> revolution. But I don't see how we can discuss evolution anymore with
> including epigenetics. Nothing can be less random, it seems, than a
> person's activities affecting their germ cells.
>

Epigenetics is about methylation, methyl groups that are added as tags to
DNA that tell RNA if it should translate a sequence into a protein or not,
those tags are the only reason liver cells are different from brain cells
even though they have identical DNA sequences. And the pattern of those
tags can change throughout the lifetime of the individual so it's not
outrageous to think that sometimes a few of those methyl groups could make
it into germ cells and thus the next generation. And there is some evidence
that on rare occasions this does in fact happen, although the effect seems
to die out after 2 or 3 generations. But even if it didn't that wouldn't
mean Lamarckian Evolution (the inheritance of acquired characteristics) has
taken over from Darwinian Evolution (random mutation and natural selection)
in its role of explaining the complexity of life.

Most, in fact nearly all, acquired characteristics are detrimental not
beneficial, that's true for all machines not just the biological type, they
are all subjected to the ravages of time, they wear out; if the
blacksmith's son inherited massive muscles in his arms from his father the
boy must also inherit burns on his arms and a broken leg that his father
received from a horse kicking him when he was working his trade. So if
Lamarckian Evolution is to explain why organisms are so well adapted to
their environment it needs a mechanism to sort out the very rare beneficia
acquired characteristics from the vastly more numerous harmful acquired
characteristics, and there is only one mechanism that fits the bill,
Darwinian Natural Selection. Most changes, regardless of it they come from
mutation or come from the life experience of the parents, are harmful, only
a very few are helpful and those few are the ones that make it into the
next generation.

There are also reasons from embryology to think acquired characteristics is
not significant to Evolution. The genome is a recipe not a blueprint and
the difference is reversibility. If you had access to my house it would be
easy to measure things and draw blueprints for it, but if would be far far
more difficult to write a recipe for it because it would have to include
detailed instructions for the workmen who built my house about what they
should do and exactly when they should to it. Even if Evolution could
somehow see the blacksmith's powerful arms it would be very difficult
verging on the impossible to translate that into a recipe.

John K Clark
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