From Gary Lawrence Murphy:

Re: Did monogamy arise to prevent infanticide? (July 29, 2013): There is perhaps a compelling argument for this from the macroevolution.net perspective: if the new hybrids were both almost infertile and quite ‘different’ from the mainstream bonobo community, considering how xenophobic the great apes tend to be, there may have been considerable danger of attack on the ‘blasphemous’ (and unusually vulnerable) young humanoids, and a strong evolutionary pressure to defend the humanoid female during her unusually long incubation and early child-care periods (ie only those who cared to defend their families could hope to reproduce into our present time)