Sunday, 20 March 2016

Spectator Review of Not in Your Genes

This is the spectator review by a post-doc in psychology.

Now there are some good references in the beginning but sadly the complaints and understanding also decline as it goes on. In particular it descends into an ad hominem attack against the author and not his work. If you are convinced of your argument why go after James and his media appearances?

The first few references seem fine about birth order and the 10,000 hours effects. Then is goes down hill. So what if 80% of genes are expressed in the brain - this tells you nothing more than the 20% that are not cannot have any effect on the brain. Why does this mean anything? Lots are house keeping genes that just keep cells alive.

The ample evidence is a meta analysis of twin studies. The problem with twin studies if the author had bothered to check is that epidemiologists now suspect that they might be flawed as they have the same exposures and circumstances. I have two children who are not twins but they share lots of views and personality traits because of their upbringing not because of their genes. It is very hard unless you separate twins to actually get good evidence for genetic as opposed to environmental effects and even then epigenetic effects might be larger than genetic effects (these follow Lamarck and not Darwin - they are "Just So Story" modifications that are directly heritable)

I will need to look at GCTA and think about how to weight that evidence.

Then there is a look at GWAS which again the review author just talks about a review chapter. I have seen the people who lead some of the major GWAS studies of disease speak and there conclusions are that the effects of genes are SO SMALL THAT THEY CANNOT BE STATISTICALLY DETECTED. The effect sizes are tiny in diabetes, heart disease and lots of less complex phenomena than learning and personality. This is because it is gene interactions that produce the effects and not single genes. This talk was from the same lecturer who cast doubt on the twin studies. The review author might like to read Prof. David Clayton's work.

Then for basic statistics he cites wikipedia. While I like wikipedia this is all credibility lost. Power calculations are a tautology. You need to know effect size and population standard deviation in order to calculate the population size that you need to use to detect the effect. This is knowing the answer before you ask the question. The last references from the Journal of Irreproducible Results (Nature) is from the News and View section, an unrefereed section where the great and the good get to spout garbage on a weekly basis.

So apart from the possible evidence from GCTA there is actually as little to support the reviewers assertions of genetic links as there is for James support that there are no genetic links. The final result is a 0-0 draw.

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