For example, it’s very difficult to understand why so many human mental disorders are common, heritable, and harmful—why wouldn’t the genetic variants that cause schizophrenia or major depression already have been eliminated by selection? Our BBS target article in 2006 addressed this.
I’ve read various discussions on this, e.g. Marco Del Giudice’s book. Just quickly skimming your article, you seem to be raising some of the same points that I saw in his book.
One question: isn’t the liability-scale heritability estimate the wrong value to use? Or at least, not straightforwardly the right one. I believe the effective heritability for the purposes of selection would roughly speaking be the prevalence times the liability-scale heritability, is that correct? So if e.g. schizophrenia has a liability heritability of 80% but a prevalence of 0.32%, that would lead to an effective heritability (for the purpose of selection) of 0.26%?
Conversely, it’s a bit puzzling that the coefficient of additive genetic variation in human brain size is lower than might be expected, according to our 2007 meta-analysis.
I’m not sure why this puzzle isn’t solved by births being a constraint?
In general, animal behavior researchers have found that even traits quite closely related to fitness (reproductive success) are still quite heritable, and still show significant genetic variance, even in ancestrally typical wild environments.
Two questions:
Could it be because they have not reached a local optimum with regards to reproductive success?
Could it be a collider/tradeoff thing? E.g. you can have a lot of offspring or you can invest a lot into the offspring you do have? So if you count the number of offspring, you don’t just get the fitness axis, but also for lack of a better word, the r-K axis.
I’ve read various discussions on this, e.g. Marco Del Giudice’s book. Just quickly skimming your article, you seem to be raising some of the same points that I saw in his book.
One question: isn’t the liability-scale heritability estimate the wrong value to use? Or at least, not straightforwardly the right one. I believe the effective heritability for the purposes of selection would roughly speaking be the prevalence times the liability-scale heritability, is that correct? So if e.g. schizophrenia has a liability heritability of 80% but a prevalence of 0.32%, that would lead to an effective heritability (for the purpose of selection) of 0.26%?
I’m not sure why this puzzle isn’t solved by births being a constraint?
Two questions:
Could it be because they have not reached a local optimum with regards to reproductive success?
Could it be a collider/tradeoff thing? E.g. you can have a lot of offspring or you can invest a lot into the offspring you do have? So if you count the number of offspring, you don’t just get the fitness axis, but also for lack of a better word, the r-K axis.