An extra sense


Eric Turkheimer


Dumb (but real and research-related) question:

Y1 = aX^2 + bX + c
Y2 = dX^2 + eX + f

What is Y1 in terms of Y2?

r/t if you know a good high school math teacher >

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A World of Their Own

There’s an interesting related  question: for a given country or geographic region, what would happen if the the rest of the world vanished?  How would they do on their own?

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There are countries where many people have cellphones, but where neither cell phones or any of their complex components are produced or designed.

More generally, there are countries that manage to implement some of the infrastructure and institutions of the industrial and scientific revolutions, but show no sign that they could have originated them. They don’t invent anything and don’t contribute to scientific progress. Sometimes a few of their natives emigrate and contribute while living in more advanced countries, but their numbers are small – in some cases close to zero.

Of course there are edge cases – countries that have contributed a few inventions and discoveries, but not very many, and few per-capita.

Considering these cases should tell us something about the necessary conditions  – especially the minimum human capital requirements –  for the industrial and scientific revolutions.  So, after looking at PRS trends in ancient DNA…



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Nulls and Norms

The neutral theory of evolution  assumes that allele frequencies change stochastically: population sizes over time matter, but there’s nothing special about any particular allele. All chance.  It can be used to develop evidence for selection: if you see results that are very different from those predicted by the neutral model, you may have a good case that some allele or alleles have been favored by natural selection.  The null model assumes zero selection.

It sound ridiculous [ and is ridiculous] , but a lot of people took this null model to be the surprise-free model, that pattern of events that happens most of the time,  like sunny days in the Atacama Desert. Not just for a single noncoding allele, but for     adaptation in general !

I remember Svante Paabo making a similar mistake: he thought that probably none of the Neanderthal alleles we picked up were adaptive: the odds were against any particular archaic allele being adaptive, but it was almost certain that some would be , for example ones that protected against regional diseases.

Move a species into a new environment, one that is survivable but noticeably different from where it originated.  What’s the probability of significant adaptive change?  100% !

One of the more amusing aspects of this weird confusion was that believing that nothing in biology made any sense was a mark of sophistication:  adaptationists were rubes. Country boys like Bill Hamilton or George Williams.

Theories in which the surprise-free prediction is something that has never, ever happened are fairly common in the softer sciences.








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The Casting Couch

I know of a few cases in which people have publicly supported the idea that humans are bosons while personally thinking otherwise. This can mean signing Graham Coop’s  letter against Nicholas Wade [ misplaced: such  letters are traditionally sent to  Pravda], or publicly criticizing work they privately agree with –  ” you have to read between the lines” -, or just being careful to avoid certain dangerous topics  – “I can’t afford to think about that”.

This tendency is strongest, perhaps, in people just entering the field. Weakest in dying Nobelists.

But life is like that sometimes.  Think of what young actresses have had to do to advance their careers.  From one point of view, they deserve respect for the sacrifice they make for their art.  In the same way, when some young geneticist is emitting protective nonsense, which can’t be comfortable – remember: it takes a hell of a man to fuck Harvey Weinstein.




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Are Samoans Big?

More to the point, are they inherently big?  Genetically big? We used to know that Samoans were big. But today it is possible, in principle  to develop a more detailed, genetical, causal explanation of Samoan bigness – although we haven’t really done so yet. And since that better explanation is possible and desirable, yet has not yet been developed, somehow we no longer know whether Samoans are inherently really big. The best is the enemy of the good. It could be some kind of optical illusion. Maybe bigness is a polygenic trait, which would have taken a million years to  select for, just as it took a million years to develop the German Shepherd or shrink dachshunds by 50%.  Maybe that bigness is unstable because polygenic, in the same way that Percherons get small if you let them watch too much vintage Steve Martin.

Now it might be that Samoans are big  in every known environment, but  that only shows how powerful and universal prejudice really is. It might be that we have spent hundreds of billions on attempts to shrink Samoans, without any lasting result, but that only shows that we haven’t tried hard enough.

If we had a PRS for bigness, and it showed that Samoans had significantly higher scores – well,  that would be a scientific travesty.  One that was especially apparent to anyone that had just gotten their Ph.D. in a related controversial field and was looking for an academic job.


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PRS and Paleoafricans

PRS scores for various traits, determined in Europeans, don’t work well for sub-Saharan Africans, due to big differences in population history.  That can in principle be fixed by doing GWAS studies among Africans.  But PRS scores determined in either Eurasians or Bantu surely won’t work with Bushmen, probably the most divergent human population.  And I can’t see how we fix this, because there aren’t enough Bushmen in the world to even do one of the required large-sample GWAS studies.

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