A common objection to using polygenic risk scores during embryo selection is that there is some risk of pleiotropy—a single gene influencing multiple traits or diseases. The concern is that trying to select against one condition could inadvertently increase the risk of others.
The more sophisticated version of this argument is an appeal to the Efficient Market Hypothesis with respect to natural selection: "If trait X is so great, why hasn't natural selection already maximized it? There must be negative second-order effects to increasing it!"
This argument isn't so silly. If I told you that there was a pill that could increase your IQ by fifteen points, would you believe me? What if I showed you a fancy-schmancy table filled with computed Hedge's g's, pristine p-values, and large N sample sizes? How about then? Still probably no. There is no trait more economically valuable than intelligence. If something like a magic intelligence pill existed--at no cost--you wouldn't be hearing about it from me.
You could argue that the same logic applies to increasing intelligence using genetics. Natural selection can be ruthless if lacking a trait proves to be a big enough disadvantage. For example, the trait "having two eyes" shows little variation among humans. And humans who do have fewer than two eyes tend to have them for reasons that aren't terribly heritable (e.g running with scissors in Kindergarten). So we have a case where an obviously beneficial trait is maximized.
But ultimately, the above argument does not go through. The sleight of hand here is a conflation between what's *natural* and what's *good*. There are traits that have only a so-so impact on fitness, but are highly esteemed based on our society's values. Intelligence is arguably one of those traits. The hubris of man be damned: We can do better than natural selection.
(I've been told that intelligence was a boon in the ancestral environment, but that the reason that intelligence isn't maximized is due to an "entropic force" due the brain having such a large mutational target, resulting in our current equilibrium distribution of the trait.)
The more sophisticated version of this argument is an appeal to the Efficient Market Hypothesis with respect to natural selection: "If trait X is so great, why hasn't natural selection already maximized it? There must be negative second-order effects to increasing it!"
This argument isn't so silly. If I told you that there was a pill that could increase your IQ by fifteen points, would you believe me? What if I showed you a fancy-schmancy table filled with computed Hedge's g's, pristine p-values, and large N sample sizes? How about then? Still probably no. There is no trait more economically valuable than intelligence. If something like a magic intelligence pill existed--at no cost--you wouldn't be hearing about it from me.
You could argue that the same logic applies to increasing intelligence using genetics. Natural selection can be ruthless if lacking a trait proves to be a big enough disadvantage. For example, the trait "having two eyes" shows little variation among humans. And humans who do have fewer than two eyes tend to have them for reasons that aren't terribly heritable (e.g running with scissors in Kindergarten). So we have a case where an obviously beneficial trait is maximized.
But ultimately, the above argument does not go through. The sleight of hand here is a conflation between what's *natural* and what's *good*. There are traits that have only a so-so impact on fitness, but are highly esteemed based on our society's values. Intelligence is arguably one of those traits. The hubris of man be damned: We can do better than natural selection.
(I've been told that intelligence was a boon in the ancestral environment, but that the reason that intelligence isn't maximized is due to an "entropic force" due the brain having such a large mutational target, resulting in our current equilibrium distribution of the trait.)