your Darwinian moral license has expired

Reviewing some of the points of contention of a drawn-out discussion, my brother writes,

3) The erudite Falk made this excellent comment:

The basis of Darwinian evolution is natural selection, not manual selection. This distinction is important because eugenics concerns only the latter and not the former. Darwinian evolution cannot be intelligently used as support for eugenics.

It is an excellent distinction. But not one, I think, that saves Darwinian evolution from lending itself to eugenics. If “human nature” is not a fixed entity, if it subject to continual development and “progress” (contra Biblical or Aristotelian notions of human nature), then it seems refashioning human nature, and the human race, is morally permissible.

I’m holding this very tentatively, because it is obviously disputable and am still considering the issues.

To that end, I hold up some issues for consideration.

First, continual development is not "progress."

Second, development makes progress possible in the same way that gravity makes defenestration possible. Newton's theory of gravity, though, doesn't make throwing someone out a window "morally permissible," nor does it "lend itself" to defenestration in any morally significant way.

Warren Falk is right: trying to monkey with evolution--it was irresistible, sorry--will always have to be done for a reason outside of evolutionary theory, without its "permission." It simply has no permission to give.