Classical and Molecular Genetic Research on General Cognitive Ability
onlinelibrary.wiley.com
onlinelibrary.wiley.com
I don't think there is any proof that eugenic policies will fail to work for GCA or even other behavioral traits that are highly heritable. See, e.g., https://infotomb.com/0q783.pdf
What's being discussed here is the historical eugenics movement. Just from the text of the article, it becomes clear that the multi-generational confounding effects like prosperity, education, and social class would make an naive effort pointless.
More generally, you should think of the problem thusly, I suggest:
Even with extensive genetic surveys, there are no clear candidates for genes that one would wish to select for that present themselves; this is consistent with the notion that general cognitive ability is evolutionarily advantageous.
It may be that g.c.a. is locally maximal; that there is no easy conflux of changes which could occur that would predictably raise the g.c.a of human individuals. A hypothetical change might for instance do something that would seem likely to increase cognitive ability, in the abstract, but carry a systemic cost that either prevents such a change from manifesting itself, or renders the value of such a change moot.
For most people, I believe, it seems intuitively clear that eugenics is analogous.
We know that eugenics efforts cannot produce any remarkable or decisive selection for increased cognitive abilities. We know this because eugenics is a sort of hobby-horse form of evolution, across handfuls of generations, and because evolution cannot, taken over thousands of generations, select any more strongly for increased cognitive abilities than it already has. If it could, it would; thus we must conclude that it can't.
We also know that eugenics requires a society that permits centralized, forcible control over how and whether individuals combine genetic material to produce offspring; it requires a society wherein all individuals can be indoctrinated so as to cooperate with this effort; it requires a society wherein these means of force and social control cannot be usurped or arrogated by elements of that society so that they may be directed towards other purposes; and it requires that this state of affairs persist for a modest number of generations, perhaps twenty to fifty.
It seems very likely that selection for eugenics is something which will fail because of the systemic costs that it would entail. In fact, it seems more likely than not that eugenics is something that would have arisen in the course of history, already --- perhaps for more trivial purposes than increasing cognitive ability --- were the social structures required not too fragile to sustain the effort.
If this argument were true then it would not have been possible for the evolution of human intelligence to have occurred.
You have assumed that having a higher gca did not have a cost higher in the past than it does now. The environment we live in today is very different to that of even our recent ancestors.
I don't buy that argument. There's no reason to think that evolution has been selecting for cognitive ability as strongly as it possibly could.
100 years ago people would have thought mental arithmetic, memorization and rhetorical speech were core parts or indicators of intelligence. I think that most people today would see creative problem solving, social empathy and long term planning as more indicative. In fact the 19th century indicators are now seen (in popular culture) as part of a disorder (autistic spectrum) that is often used to explain the behaviour of otherwise incapable people.
Our culture, communities and technology define our humanity, creating a greater humanity through breeding misses the point somewhat.
Of course this does not mean eugenics is a desirable activity that we should be engaged in, but I have not seen any rational argument that it has been “proved" to be impossible.
Also I don't think it's agreed.
Also it's not clear that your statement that population level changes can be created by selective breeding is true - if a characteristic is dictated by alleles that damage fertility or other fitness indicators then it may well not be continuous. In the case of human intelligence the increased child birth mortality associated with large heads and the increase dependence of infants on parents are examples. There may be others which are more relevant to modern life, like propensity to depression, disinterest in sex etc (note : I am using these as examples, not saying that this is so).
Use whole-genome mutagenesis and increase the size of your population. This will reduce the total number of generations that you require to find the novel mutations that you seek.
Of course selecting only for GCA may well increase the frequency of other phenotypes, but unless GCA is directly linked to that phenotype then there is no reason you can’t select against any undesired phenotype at the same time. This is done all the time with the selective breeding of animals and plants. I know of no phenotype shared by all individuals with a high GCA so there should be no phenotype that would inherently be a consequence of selecting for high GCA, certainly not infertility.
A baby monitor with progress notes on various pivot options sounds great. (Revolutionary Girl Utena model Serta...) It beeps if all the child's career options are deprecated by the next 15 years, and points to an appropriate hill near which those careers fester; or if their social health role is to force vulnerable mutations in (otherwise) epidemic disease (I'm only a Doctor ironically, etc.)