Not skin deep

Basque communist Maju thinks this study indicates "patterns of inter-population differentiation are stronger in the genes of appearance mostly" and "the actual underlying differences between populations [. . .] are invariably much smaller than it looks".

But this is not what the paper shows at all. The single most highly population-differentiated gene group in the authors's analysis relates to pituitary gland development. Next comes dorsoventral neural tube patterning. Then some low-level cellular functions, more brain development, sperm motility and development, and thyroid gland development. Pigmentation comes about halfway down the list and hair follicle development below that.

The placement of pituitary- and thyroid-related genes near the head of the list brought to mind Carleton Coon's comments on endocrines and racial differences in temperament.


Nanonymous said...

Don't overlook the category "vesicle docking during exocytosis". That's both hormonal secretion and neurotransmitter release/cell communication.

coldequation said...

That also reminds me of the breeding experiment that tamed Russian silver foxes - as I recall, there were some major endocrine changes.

coldequation said...

Neural tube changes were a big difference too, and they apparently had a lot to do with coloring changes. Skin, hair, and nervous tissue are all related, all part of the ectoderm in embryos. That has something to do with the fact that tame animals tend to be colored differently than wild animals - like how many domesticated animals have spots like Holstein cows.

I'm not sure how this applies to humans. If you look at the biochemical pathways that make melanin, they involve chemicals that are important in the nervous system, but I don't know what that actually means.

n/a said...


Coon believed the amount of light passing through the retina affected behavior, and reported that the color of the retina follows that of the skin.

As far as I know, none of the loci so far found to be associated with pigmentation in humans have any direct connection to neural tube patterning.