orthonormal comments on Open Thread: August 2009 - Less Wrong

5 Post author: taw 01 August 2009 03:06PM

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Comment author: taw 01 August 2009 06:54:15PM 3 points [-]

A very common belief here is that most human behaviour is based on Paleolithic genes, and only trivial variations are cultural (memetic), coming from fresh genes, or from some other sources.

But how strong is the evidence of Paleogenes vs memes vs fresh genes (vs everything else)?

Fresh genes are easy to test - different populations would have different levels of such genes, so we could test for that.

An obvious problem with Paleogenes is that there aren't really that many genes to work with. Also, do we know of any genetic variations that alter these behaviours? If preference for large breasts was genetic, surely there might be a family somewhere with some mutation which would prefer small breasts. Do we have any evidence of that?

So I suspect memes might be much more important relative to Paleogenes than we tend to assume.

Comment author: orthonormal 01 August 2009 07:36:48PM 3 points [-]

If preference for large breasts was genetic, surely there might be a family somewhere with some mutation which would prefer small breasts. Do we have any evidence of that?

Brain-coding phenomena like sexual preferences seem to be built from large collections of genes that are interconnencted with other systems, such that there aren't many possible mutations that would undo the feature without wreaking havoc elsewhere in the phenotype as well.

In fact, the universality of such preferences across neurologically intact humans is evidence that they come from Paleogenes rather than memes or fresh genes, either of which can more easily be altered without deleterious effects elsewhere.

Comment author: taw 01 August 2009 10:15:39PM 1 point [-]

I'm not saying Paleogenes are not a possible explanation, but I haven't seen much in terms of such evidence like:

  • I don't think it's so common for people to go around the world, and actually verify that people in statistically significant number of virtually isolated tribes do have preferences for larger breasts etc. So universality is more postulated than actually empirically found. Even if you find extremely common behaviour, it can still be memetic, as a lot of memes are copied from parents to children. How many behaviours are empirically known to be universal?
  • Mutations to such genes would be non-lethal, and some would only mildly reduce inclusive fitness. We have plenty of genetic diseases in the population affecting more important genes. So how come we haven't discovered mutations in the wild that alter genes controlling this supposedly genetic behaviour.
  • We know very few genes obviously linked with behaviour, and saying it's coded by emergent interaction of multiple genes is just handwaving away the problem. There's a pretty low ceiling of how much can be straightforwardly coded this way, and I'd expect some serious evidence of some mechanism of complex genetically coded behaviour.
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