I came across information about this disease when doing a search for chemical and molecular structures of hair. When I specifically searched for difference in SULFUR content, I came across many articles citing this disease. It's very interesting that you came across COPPER differences as well.
The reason I was even looking for this was because I searched a long time ago for structural (at the molecular/chemical level)differences in the hair itself among the different hair types, and I came across an article that actually cited the percentages of chemicals/materials of different hair types. I can NOT find the article again. I am hoping I saved it at work! I am currently on maternity leave.
As far as the old argument about a hot climate being the cause for kinky hair, I am not sure that argument still has value. Parts of Asia are also very hot, and well you know their hair is not kinky. Regarding the East Indians and other peoples of Mediterranean descent, remember that East Indian is not really a 'race', and that these people and other middle Easterners are the result of long term mixing. East Indians, I've read, originally descended from a group of Africans. I imagine that over time they mixed with Asians, and then eventually Europeans, creating the look we think of as Indian, but you can still see more black looking E. Indians, or Asian looking E.Indians, or more white looking E. Indians. Just like latinos are a mixture of many.
I don't think that kinky hair is the result of a disease, but I have wondered, that aside from follicle shape differences, how is the hair different at a microscopic level? I do not think that all kinky hair is merely super curly straight hair, so that has led me to wonder about differences in things such as sulfur content etc., esp. after people reported softer new growth with the MSM. What do you think?