I dont think this is necessarily true.
If you look at the type of hair that Black Africans (who were born in Africa) have it ranges from type 1 to type 4...look at the hair types of ethopians and somalians, etc.
Scientists are proving that the the genes for all types of hair is part of the African genotype as are the genes for every type of skin color and phenotype. In other words, Africans are the most genetically diverse people on earth.
There are interesting studies being done which show gene frequency correllations between people in disparate areas of the earth and the area they likely originated from in Africa. For example, people from southeast Asia seem to have relatives in the nigerian region of africa. I'll look for a link to this particular study and post it.