
Classical and Molecular Genetic Research on General Cognitive Ability - luxoria
http://onlinelibrary.wiley.com/enhanced/doi/10.1002/hast.495
======
danieltillett
Does anyone know what the proof was that proves eugenics can't work for
raising gca? This is stated as fact in the paper (reference 32).

~~~
escape_goat
> ...research like that in which contemporary behavioural geneticists engage
> helped to undermine the eugenics movement by proving that eugenic policies
> could not achieve their stated goals.

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.

~~~
hugh4
>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.

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.

~~~
sgt101
It's simple to say "let's have a fatter cow". It is not simple to say "let's
have a more intelligent human" because "intelligent" is not a fixed or agreed
term.

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.

~~~
danieltillett
Intelligence might not be a fixed or agreed term, but GCA is fixed and agreed.
If you can measure a genetic trait, and the trait varies in the population,
then you can bring about population level changes in this trait via selective
breeding.

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.

~~~
sgt101
I think GCA originated in 1954; I don't know how many generations of people
breeding it would take to get a selected trait - humans are genetically very
similar compared to other species; there is not much variation... so I don't
have any idea of what the breeding program length would be, but I assume that
it would be several generations... so I don't think that an idea that has been
around for 60 years would really qualify as fixed and agreed in that time
scale.

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).

~~~
danieltillett
If there are some individual in the population with the particular phenotype
you are selecting who are not infertile then selective breeding can increase
the frequency of that phenotype in the population. In the case of GCA we know
that there are fertile individuals with very high GCA so we know it is
possible to selectively breed for high GCA.

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.

