"And Yet It Moves"

I have twice promised to keep you up-to-date with a couple of genetic controversies but have not done so. This is largely because the issues have gotten out into mathematical and biological specialties that are entirely beyond me, and I am less and less able to extract information from all the brilliant people on my sidebar and put it into take-home paragraphs.  I have scraps, occasionally connected by rubber bands that I actually understand. 

As far as I can tell, one of the controversies is rather amiable, with everyone agreeing that Population Y, a substrate of some tribes in the upper Amazon, greatly predates the bulk of New World settlement, and is quite different from any of the three known waves into the Americas, all of which came in via Beringia. It seems more closely related to Southeast Asia and Oceania, to Papuans and Andamanese than to the ANE (Ancestral North Eurasians) and NEA (Northeast Asians) identified as the populations which mixed west of Beringia before tha long migration to the New World.  However, everyone also agrees that there are problems with the data that are present. Contamination has not been entirely ruled out in the samples, though the results look robust enough to withstand some discovered contamination from more recent sources (either in the ground or in the labs). The dating of samples is disputed. Not all Amazonian populations show the substrate, which is surely unusual after 20,000+ years of tribes living near each other and exchanging (or stealing) wives. Most importantly, all the explanations of how that genetic material could have gotten there have difficulties. Across both the Pacific and Andes? Then why no trace in the Andes? Coastal Beringia and western North America? Then why are there no traces of them until South America?  And far inland. So when and and how the DNA got here can get people worked up, and everyone agrees it's not even proven.  But there it is, until a better explanation comes along.

 

 The second controversy is more rancorous, as nature-nurture usually is.  While 'nurture' controls the cultural narrative, 'nature' has racked up victories for years. Those who strongly favor the environmental, keep insisting that nature can't be the main driver - the geneticists must not have looked under the seat cushions or something. But recently there has been a sharp check in the heritability juggernaut. That a large factor of randomness, or 'unshared environment' is in the mix we already knew.  However, while genetics has been doing a good job in predicting phenotypes (with that limitation), when we take the pieces apart they don't add up to the expected percentage.  It is called missing heritability, and people are quite nasty about it.  I wonder if the the nastiness is driving people to make stronger claims than are warranted. 

When it became clear that polygenic traits were the norm,  there was blithe confidence that we would find the additive combinations pretty quickly.  If we could predict IQ within 0.5SD with 80% accuracy, finding 20% seemed like a great start.  More brute force calculations, drawing more lines in the network, would soon solve the problem. It hasn't. Researchers who are taking a hardline approach to proof are saying it's only 30%, rather like the preacher in black churches who sends back the collection plate saying "It's not enough!"  Suddenly it is the strong nurture group that is complaining about the change under the seat cushions.  Don't tell me it's not there.  It has to be there. It fits the predictions.  It fits real life.  Not so fast. Yes they have allowed that there might be cross-influences at deeper and deeper levels, of SNPs speeding up or slowing down expressing, turning the lights on and off in response to other SNPs acting on them. But "Said the Pieman to Simple Simon, first show me your money."  

Yes, environment might creep back in after all, particularly WRT chemical exposures affecting not only final-product expression, but light-switches in every room along the tunnel. Novel chemicals might bind to receptors developed over hundred of generations of evolution for unrelated reasons. Some receptors will show out to profligately bind to lots of unexpected substances, others will be more choosy.