So basically what he's saying that once the women got too old the men stopped having sex with them and there was no longer any point in being fertile because the ladies weren't getting any action?
JMO but I'm not too sure I believe this theory that preferential mating explains why fertility in older women died out. Women don't have to be a man's preferred mate to become pregnant, they just have to have sex with a fertile male, and many older women have no problems finding a male to have sex with even if the guys might rather be out having fun with eighteen year old twins with big *advertiser censored*.
I think it's more to do with the long life span of humans and the relatively long time that the offspring needs their parents to survive and prosper. The risks of pregnancy rise as women grow older, both for the woman and the baby, even with the current state of medical care today, and I expect they may have done so even in the early days. The grandmother theory seems to have some merit as an active grandparent may help in the child rearing and increase the children's chances of growing up, but I think that considering the long time that human children are somewhat dependent on their parents it might have been an advantage for the existing children if the mother stopped reproducing after having them, so A) she didn't die in childbirth in her next pregnancy, leaving her little ones orphaned and without care B) she had a chance to feed all of her brood because there weren't so many C) she wasn't as tempted to throw her previous little olive branches into the wilds to take care of themselves because she had her hands so full. And D) there would have been little point in being fertile after the age that you were likely to die before you had managed to raise your last child.
These days women may of course live happily for decades after their last child has left the nest but the life expectancy used to be much shorter when this all this evolutioning was taking place and many women would have died well before the current menopausal age anyway.
Another thing to consider is that with females, chromosomal abnormalities increase with the mother's age, so if 60- or 70 year olds were having babies they could be too ill to survive anyway, even if the mother lived long enough to feed them until they could fend for themselves. So there could have been little point evolutionarily in using scarce resources to nurture pregnant elderly ladies who would give birth to babies who were unlikely to survive into adulthood.
:cow:
