The Mechanism: Dead Genes or Fast Moving Enzymes?

In my last post, I discussed the mathematical unlikelihood of polygenic contributions to a heritable trait or disorder.  Let's say you simply refuse to give up the ship.  You just want to believe that there is a magical cascade of interactions between tens of thousands of genes that confer the phenotype you are looking for.  Shortly, I will have a question for you...

The Contradiction Between "Polygenic" Traits and High Heritablity

When I was critiquing genetic linkage studies back in the day, almost all of the studies would include something in the abstract about the trait they were looking at (intelligence, schizophrenia, depression, etc.) being “highly heritable,” as if this somehow lent credence to the results of the study.  After repeated failures to replicate, a new view of the genetic bases of of these disorders began to emerge and is now quite popular and accepted as a given by most scientists in the field, as far as I can tell.  I think it is best exemplified by a quote from this piece:

“Complex traits are just that—complex. Most traits are incredibly polygenic, likely involving tens of thousands of loci. These loci will act via a vast number of pathways”.

Polygenic Scores are the New Black?

When I was criticizing genetic linkage studies in the early 2000's,  genome-wide association studies (GWAS) were all the rage.  These appeared to FINALLY be falling out of favor, due to their propensity to generate false positives.  Good riddance...  Unfortunately, like a hydra, They return with a vengeance, and with a second head:  Genome-wide Polygenic Scores.  The idea here is that one can take  thousands of genetic markers from a GWAS and find common matches for individuals sharing a particular trait.  I can see where this idea is going to appeal to a younger set of scientist brought up in the age of artificial intelligence, but I believe that we are again looking at a clever way to suggest that traits have genetic linkages, when in fact this type of analysis, at least on my first glance, appears to do nothing of the kind.