I have a very good understanding of modern evolutionary theory, much of it gleaned from Sarah Hrdy. Here are some quotes from her that I've used in some of my many stories on this general topic.
"The great anthropologist and comparativist Sarah Hrdy tells us that, across species, including among humans, the best mother for many eons was the one who was, under particular and far-from-rare ecological circumstances, promiscuous. By being so, she could hedge against male infertility, up her odds of a healthy pregnancy and robust offspring, and create a wider network of support by lining up two or three males who figured the offspring might be theirs."
"As primatologist Sarah Hrdy observed, “To Darwin, elusiveness was as integral to female sexual identity as ardor was to that of their male pursuers.” And the stakes of this distinction between male and female, ardent and elusive, active and passive, coy and eager, selfish and tender, were high. Indeed, all of civilization, Darwin and his contemporaries suggested, hung in the balance." (She's speaking here to Darwin's erroneous Victorian understanding of human mating)
Sarah Hrdy talks in Mothers and Others about the cooperative breeding model. Perhaps you should go back and re-read.
And if you think the human cervix serves no purpose, there is nothing left for me to do but to laugh at you and call it a day since that is quite possibly the most absurd thing I've ever heard anyone say ever. Clearly, biology is not your field.
Oh, and by the way...
"There are many genetic incompatibilities that prevent offspring, such as incompatible blood group, guaranteed-lethal recessive gene defects, etc.."
"Yes, this is possible and in fact already happens in humans causing apparent infertility in couples (alongside a host of other sexual reproducing organisms). Consider for instance variations in two genes encoding for proteins in the eggcoat, ZP2 and ZP3, and another gene encoding for a sperm protein that latches onto the eggcoat, C4BPA. Each of these three come in various, in themselves stable and viable, forms, but the end result is that a male with one form of C4BPA cannot produce offspring with women with particular forms of ZP2 and ZP3 because the sperm fails to latch onto the eggcoat because of shape differences of the proteins. See here for details."
