I read with great interest Akrami and Osati’s article entitled ‘Is consanguineous marriage religiously encouraged? Islamic and Iranian considerations’ published in the March 2007 issue of the Journal of Biosocial Science (Akrami & Osati, 2007). The authors showed that in many Islamic sources, there is no sign that could be described as encouraging cousin marriages. I would like to make a few comments about it.

Unquestionably, aggregate-level correlations are in most cases higher than individual-level correlations. For example, in the National Longitudinal Survey of Youth (NLSY) in the United States, the correlations are 0·487 between adolescent IQ and log-transformed adult income, 0·449 between years of schooling and adult income and 0·626 between years of schooling and IQ (N=6064). The corresponding country-level correlations are 0·815, 0·816 and 0·788 (N=125 countries).

I thank Dr M. Saadat for taking the time to carefully read this article (Akrami & Osati, J. biosoc. Sci.39, 313–316) and for making helpful comments. After studying his input, I believe he is in agreement with our conclusion that there is no encouragement of consanguineous marriage in the Islamic context. As he stated, it highlights the importance of the historical background of such practice in some parts of Iran. However, I believe this statement may not be applicable to the entire country. He is right with his second comment regarding Imam Ali and the Fatima family relationship.