Interesting. As you probably know, on the classic neo-Darwinian theory of sex developed by Hamilton, Williams and Maynard Smith the ONLY reason for reproducing sexually vs. asexually is faster adaptation and mutation to avoid disease and parasites. That the bonobos reproduce often with many different partners suggests very rapid mutation and thus a great resistance to disease, meaning a low rate of std's. I would guess that those born with birth defects would be neglected. Hope I got that right;-)
Sam Pawlett