Birth order in transgendered males from Polynesia: a quantitative study of Samoan fa'afāfine.

In previous research, a late birth order has been shown to be a characteristic of Western homosexual transsexual men. To date, however, it is not clear if a late birth order is specific to Western transsexuals or may be a characteristic of non-Western transgendered males as well. We quantified birth order in a sample of 13 transgendered males known as fa'afāfine from Samoa. On average, the fa'afāfine were late born, both with regard to number of older brothers and number of older sisters, although the effect appeared to be somewhat stronger with regard to number of older brothers. We consider possible interpretations of the late birth order effect, along with recommendations for further research to identify common mechanisms that might underlie transgenderism across different cultural groups.