so, the tidbit of info in the previous post about the mccoy clan being predisposed to von hippel–lindau disease (75% of the mccoy clan have had tumors on their adrenal glands — says so in wikipedia so it must be true), got me to thinking about what sorts of congenital conditions might offer clues to “genes for altruism” a la cochran, hardy & harpending [pdf].
re. the mccoys and von hippel–lindau disease:
“Some descendants of the McCoy family (involved in the Hatfield-McCoy feud of Appalachia, USA) as well as the Elliotts have VHL. In an article appearing in the Associated Press, it has been speculated by a Vanderbilt University endocrinologist that the hostility underlying the Hatfield–McCoy feud may have been partly due to the consequences of von Hippel–Lindau disease. The article suggests that the McCoy family was predisposed to bad tempers because many of them had a pheochromocytoma, which produced excess adrenaline and a tendency toward explosive tempers.“
hmmm. excess adrenaline. that could certainly be beneficial if the sort of altruistic behavior you need to have to be reproductively successful is the kind where you’re willing to go out and fight the competing clan on behalf of your own.
so i started thinking about everybody’s favorite aggressively tribal inbreeders — the arabs — and aaaall the congenital disorders they have and if any of them might be related to adrenalin and/or the adrenal glands.
here’s one — congenital adrenal hyperplasia:
“Congenital adrenal hyperplasia (CAH) refers to any of several autosomal recessive diseases resulting from mutations of genes for enzymes mediating the biochemical steps of production of cortisol from cholesterol by the adrenal glands (steroidogenesis)…. CAH is a genetic disorder in which girls are masculinized because the adrenal glands secrete large amounts of androgen during prenatal development. The extra androgen does not affect a baby boy’s physical development, but in baby girls it can enlarge the clitoris so that it resembles a penis….
“Most of these conditions involve excessive or deficient production of sex steroids and can alter development of primary or secondary sex characteristics in some affected infants, children, or adults.”
so here’s a genetically recessive condition — so, like sickle cell anemia, you need to have two copies of the “bad” allele to have the condition — that masculinizes girls ’cause the female fetus is exposed to lots of androgen. and male fetuses are not affected? at all? couldn’t they be “extra” masculinized in some way? maybe that’s not the case, but it sure makes me wonder.
and androgen certainly has interesting effects on the brain:
“Circulating levels of androgens can influence human behavior because some neurons are sensitive to steroid hormones. Androgen levels have been implicated in the regulation of human aggression and libido.”
well, what do you need to survive in a warring clannish/tribal society but high levels of aggression? amirite?!
the world-wide incidence of CAH is 1:14,199 live births. in kuwait it’s 1:7,000 and amongst moroccan jews it’s between 1:5000-1:7000 (i know, i know — they’re not arabs — but they’re part of the same sort of clannish, inbreeding society being in morocco). there are also apparently high rates in egypt (alexandria), but i don’t know what the prevlance is. it’s also considered a problem in tunisia, jordan, oman, uae and saudi arabia.
here’s a breakdown of the prevalence in several populations:
1:282 – yupik eskimos of southwestern alaska
1:2,141 – edit: la reunion, france (or la reunion, france? see comments.)
1:5000-1:7000 – moroccan jews
1:7,000 – kuwait
1:10,866 – france (whites)
1:10,866 – italy (whites)
1:14,500 – new zealand
1:15,800 – japan
1:17,098 – scotland
carriers of one allele related to CAH often exhibit “symptoms of androgen excess.”
androgen excess? aggression? high prevalence in the arab world? clannish/tribal societies? possible “genes for altruism”?
dunno. just a thought.
(note: comments do not require an email. chaaaaaaarge!)