Scent of father checks daughter's maturity. Basically the authors found in a survey that if biological fathers are around, girls mature more slowly. This sounds like the Harpending-Draper model of father absence, though with a somewhat more biological edge. The researchers suggest that the late maturity reduces the risk of inbreeding. Frankly, I'm skeptical that that is it, many animals do have pheromonally sensitivities which seem to adopt a "near enough" & "not too far" strategy for genetic diversity & compatibility, but humans seem a bit better at kin recognition than say...guppies. And, I don't get the impression that they controlled for the possibility that the types of fathers who are impulsive and abandon their families are also passing on genes for faster maturity to their daughters (it could get a genetic correlation, or, pleiotropy). Nevertheless, the principle is interesting as it is likely real, as judged by MHC studies which show different preferences of females for the smell of related & unrelated males (with some genomic imprinting twists). Finally, I do find the possibility that urban areas accelerate development of note. I suspec there's something there.