Right. Though below Tim notes one truism: on a continuous trait with a non-trivial heritability (IQ) you likely don’t have strong long-term unidirectional fitness implications. Otherwise, all the genic variance would be gone (strong selection + high heritability).
That truism doesn’t sound right to me, but maybe I don’t understand it. In the long term, you have equilibrium, but that doesn’t mean fixation for genes of small effects, because there are always new mutations. There is an equilibrium between deleterious mutation and selection driving out the mutations; and this is somehow balanced between, say, height and IQ. And none of this is to say there was long-term upward pressure on either trait.
Looking at your comment I am not sure we disagree. Rather than unpacking what I’m trying to get at (which is orthogonal to the discussion), I’ll leave it be. But if you are curious look up “heritabitility” in Hartl & Clark, they explain the issues more lucidly than I could here.
Right. Though below Tim notes one truism: on a continuous trait with a non-trivial heritability (IQ) you likely don’t have strong long-term unidirectional fitness implications. Otherwise, all the genic variance would be gone (strong selection + high heritability).
That truism doesn’t sound right to me, but maybe I don’t understand it. In the long term, you have equilibrium, but that doesn’t mean fixation for genes of small effects, because there are always new mutations. There is an equilibrium between deleterious mutation and selection driving out the mutations; and this is somehow balanced between, say, height and IQ. And none of this is to say there was long-term upward pressure on either trait.
Looking at your comment I am not sure we disagree. Rather than unpacking what I’m trying to get at (which is orthogonal to the discussion), I’ll leave it be. But if you are curious look up “heritabitility” in Hartl & Clark, they explain the issues more lucidly than I could here.