If you can't establish a biological race to test, then your correlation is one of social, not biological categories. If race is half of the correlation to be explained, then yes, you really do have to know that you are actually testing a human subspecies, and doing that has precisely the problems I have specified. Please provide data. What we have is measurements of Neanderthal brain cases with estimates based on the relation of brain case size to brain mass in measured populations. Correlations do not equal cause.
Science involves sorting our specious correlations from causal relations.
Criticize the specifics, not the general approach. Gee, I thought I was talking about sorting specious correlations from causal relations. What methods are you talking about. This is way too glib for me to understand. Modern medicine is just as pragmatic as ancient medicine.