You may be thinking of the fact that Muhammad married and had sex with Ayesha when she was somewhere between 9 and 11 years old. This early onset of puberty is not peculiar to the Semitic peoples, there's a wide spread in all racial types. One of my UK colleagues has a daughter who has begun to menstruate at 9 years old, but his wife apparently did not begin until she was 14 (too much information, Andy!).
