While tromping through a blizzard, seeking insight into circum-polar peoples, I discovered a condition called chilblains. The relevant Wikipedia page is rather short:
Chilblains … is a medical condition that occurs when a predisposed individual is exposed to cold and humidity, causing tissue damage. It is often confused with frostbite and trench foot. Damage to capillary beds in the skin causes redness, itching, inflammation, and sometimes blisters. Chilblains can be reduced by keeping the feet and hands warm in cold weather, and avoiding extreme temperature changes. Chilblains can be idiopathic (spontaneous and unrelated to another disease), but may also be a manifestation of another serious medical condition that needs to be investigated.
The part they don’t mention is that it can really hurt.
The first HBD-related question I became interested in–after visiting a black friend’s house and observing that she was comfortable without the AC on, even though it was summer–is whether people from different latitudes prefer different temperatures. It seems pretty obvious: surely people from Yakutsk prefer different temperatures than people from Pakistan. It also seems easy to test: just put people in a room and give them complete control over the thermostat. And yet, I’d never heard anyone discuss the idea.
Anyway, the perfunctory Wikipedia page on chilblains mentioned nothing about racial or ethnic predisposition to the condition–even though surely the Eskimo (Inuit) who have genetic admixture from both ice-age Neanderthals and Denisovans:
“Using this method, they found two regions with a strong signal of selection: (i) one region contains the cluster of FADS genes, involved in the metabolism of unsaturated fatty acids; (ii) the other region contains WARS2 and TBX15, located on chromosome 1.” …
“TBX15 plays a role in the differentiation of brown and brite adipocytes. Brown and brite adipocytes produce heat via lipid oxidation when stimulated by cold temperatures, making TBX15 a strong candidate gene for adaptation to life in the Arctic.” …
“The Inuit DNA sequence in this region matches very well with the Denisovan genome, and it is highly differentiated from other present-day human sequences, though we can’t discard the possibility that the variant was introduced from another archaic group whose genomes we haven’t sampled yet,” Dr. Racimo said.
The scientists found that the variant is present at low-to-intermediate frequencies throughout Eurasia, and at especially high frequencies in the Inuits and Native American populations, but almost absent in Africa.
Sub-Saharan Africans have their own archaic admixture, but they have very little to no ice-age hominin–which is probably good for them, except for those who’ve moved further north.
Imagine my surprised upon searching and discovering very little research on whether chilblains disproportionately affects people of different races or ethnicities. If you were a dermatologist–or a genetically prone person–wouldn’t you want to know?
So here’s what I did find:
Black individuals have been shown to be 2 to 4 times more likely than individuals from other racial groups to sustain cold injuries. These differences may be due to cold weather experience, but are likely due to anthropometric and body composition differences, including less-pronounced CIVD, increased sympathetic response to cold exposure, and thinner, longer digits.3,6
I think CIVD=Cold-Induced Vasodilation
The Military Surgeon: Journal of the Association of Military Surgeons of the United States, Volumes 36-37, states:
The text continues with descriptions of amputating rotting feet.
A PDF from the UK, titled “Cold Injury,” notes:
Notice that the incidence of chilblains is actually less in extremely cold places than moderately cold places–attributed here to people in these places being well-equipped for the cold.
Finally I found a PDF of a study performed, I believe, by the US Military, Epidemiology of US Army Cold Weather Injuries, 1980-1999:
While I would really prefer to have more ethnic groups included in the study, two will have to suffice. It looks like trench foot may be an equal-opportunity offender, but chilblains, frostbite, and other cold-related injuries attack black men (at least in the army) at about 4x the rate of white men, and black women 2x as often as white women (but women in the army may not endure the same conditions as men in the army.)
On a related note, while researching this post, I came across this historic reference to infectious scurvy and diabetes, in the Journal of Tropical Medicine and Hygiene, Volumes 4-5 (published in 1902):
Note: this is why it is important to discard bad theories after they’ve been disproven. Otherwise, you kill your scurvy victims by quarantining them instead of giving them oranges.