fitness in the wild is very seldom improved by loss-of-function mutations, whereas fitness for our purposes, starting from the species that have been evolving for fitness in the wild, very often is.
There’s no reason evolution would have already have optimized for all the intelligence-related alleles; if it had, they would have reached fixation.
Rapid success at breeding larger corn kernels is not going to generalize into rapid success at breeding ubermensch.
I think it is. All the genetic data seems to point to: much of intelligence is genetic, highly polygenic, not fixated, and additive. All of that translates to breedability: we have a lot of easily identified variants present in only parts of the population; hence, breedable.
There’s no question that evolution can continue. The issue is that the rate you can attain for different traits differ. For example, evolving smaller animals from larger animals (by a given factor) is an order of magnitude faster process than evolving larger animals from smaller animals. ( http://news.ucsc.edu/2012/01/body-size.html ). I think you wouldn’t disagree that it would be far quicker to breed a 50 point IQ drop than 50 point IQ rise?
we have a lot of easily identified variants present in only parts of the population
I guess you refer to those studies on intelligence genes which flood the popular media, which tend to have small effect sizes and are of exactly the kind that is very prone to superfluous results.
For example, evolving smaller animals from larger animals (by a given factor) is an order of magnitude faster process than evolving larger animals from smaller animals. ( http://news.ucsc.edu/2012/01/body-size.html ). I think you wouldn’t disagree that it would be far quicker to breed a 50 point IQ drop than 50 point IQ rise?
But what does that have to do with breeding for our objective purpose? It may be easier to destroy functionality than create it, but evolution is creating functionality for living in the wild and doing something like hunting mice while we’re interesting in creating functionality to do something like understand human social cues and trading off against things like aggression and hostility towards the unknown. In both cases, functionality is being created and trading off against something else, and there’s no reason to expect the change for one case to be beneficial for the other. Border collies may be geniuses at memorizing words and herding sheep and both of these feats required intense selection, but both skills are worse than useless for surviving in the wild as a wolf...
I guess you refer to those studies on intelligence genes which flood the popular media, which tend to have small effect sizes and are of exactly the kind that is very prone to superfluous results.
The original studies, yes, the ones like candidate-gene studies where n rarely is more than a few hundred, but the ones using proper sample sizes like n>50000 and genome-wide significance level seem trustworthy to me. They seem to be replicating.
Well, my point was that you can’t expect the same rate of advances from some IQ breeding programme that we get when breeding traits arising via loss-of-function mutations.
Sure, there’s a huge genetic component, but almost none of it is “easily identified”.
Generally you can expect that parameters such as e.g. initial receptor density at a specific kind of synapse would be influenced by multiple genes and have an optimum, where either higher or lower value is sub-optimal. So you can easily get one of the shapes from the bottom row in
i.e. little or no correlation between IQ and that parameter (and little or no correlation between IQ and any one of the many genes influencing said parameter).
edit: that is to say, for example if we have an allele which slightly increases number of receptors on a synapse between some neuron type A and some neuron type B, that can either increase or decrease the intelligence depending on whenever the activation of Bs by As would be too low or too high otherwise (as determined by all the other genes). So this allele affects intelligence, sure, but not in a simple easy to detect way.
There’s no reason evolution would have already have optimized for all the intelligence-related alleles; if it had, they would have reached fixation.
I think it is. All the genetic data seems to point to: much of intelligence is genetic, highly polygenic, not fixated, and additive. All of that translates to breedability: we have a lot of easily identified variants present in only parts of the population; hence, breedable.
There’s no question that evolution can continue. The issue is that the rate you can attain for different traits differ. For example, evolving smaller animals from larger animals (by a given factor) is an order of magnitude faster process than evolving larger animals from smaller animals. ( http://news.ucsc.edu/2012/01/body-size.html ). I think you wouldn’t disagree that it would be far quicker to breed a 50 point IQ drop than 50 point IQ rise?
I guess you refer to those studies on intelligence genes which flood the popular media, which tend to have small effect sizes and are of exactly the kind that is very prone to superfluous results.
But what does that have to do with breeding for our objective purpose? It may be easier to destroy functionality than create it, but evolution is creating functionality for living in the wild and doing something like hunting mice while we’re interesting in creating functionality to do something like understand human social cues and trading off against things like aggression and hostility towards the unknown. In both cases, functionality is being created and trading off against something else, and there’s no reason to expect the change for one case to be beneficial for the other. Border collies may be geniuses at memorizing words and herding sheep and both of these feats required intense selection, but both skills are worse than useless for surviving in the wild as a wolf...
The original studies, yes, the ones like candidate-gene studies where n rarely is more than a few hundred, but the ones using proper sample sizes like n>50000 and genome-wide significance level seem trustworthy to me. They seem to be replicating.
Well, my point was that you can’t expect the same rate of advances from some IQ breeding programme that we get when breeding traits arising via loss-of-function mutations.
They don’t seem to be replicating very well...
http://arstechnica.com/science/2014/09/researchers-search-for-genes-behind-intelligence-find-almost-nothing/
Sure, there’s a huge genetic component, but almost none of it is “easily identified”.
Generally you can expect that parameters such as e.g. initial receptor density at a specific kind of synapse would be influenced by multiple genes and have an optimum, where either higher or lower value is sub-optimal. So you can easily get one of the shapes from the bottom row in
http://en.wikipedia.org/wiki/Correlation_and_dependence#/media/File:Correlation_examples2.svg
i.e. little or no correlation between IQ and that parameter (and little or no correlation between IQ and any one of the many genes influencing said parameter).
edit: that is to say, for example if we have an allele which slightly increases number of receptors on a synapse between some neuron type A and some neuron type B, that can either increase or decrease the intelligence depending on whenever the activation of Bs by As would be too low or too high otherwise (as determined by all the other genes). So this allele affects intelligence, sure, but not in a simple easy to detect way.