By the way, as far as your "math" goes, i frankly find hilarious the implicit assumption that rape is necessarily an effective means of reproduction. If a woman who is nursing is raped, the probability of conception is extremely low.
I’ve heard that breastfeeding can keep me from getting pregnant. Is this true?”
Yes, as long as you nurse according to the rules of natural child spacing. The same hormones that make milk suppress the release of reproductive hormones. While breastfeeding full-time most mothers do not ovulate and do not have menstrual periods. This means that you can’t get pregnant, at least for a while. It’s as if your body is telling you, “Nourishing one baby is all you can handle at the moment. It’s too soon for a sibling.”
If a woman is raped during her menstrual cycle, the probability of conception is very low.
It's possible — but highly unlikely. You'd have to have a very short menstrual cycle, which is the time from the first day of one period to the first day of the next period, or a tendency to have long periods. This would bring the time of ovulation closer to the time when you would start bleeding.
Conception occurs when an egg and sperm meet in a fallopian tube. Sometime during the middle of your menstrual cycle, most likely between the 12th and 16th days, an egg reaches maturity in one of the two ovaries. The ovary releases the egg into the abdomen, where it's quickly sucked up by the tulip-shaped opening of the nearest fallopian tube.
An egg can survive in your fallopian tube for about 24 hours after it's released from the ovary. So the only way you can get pregnant is if sperm are present in your fallopian tube during this window of opportunity. If the egg isn't fertilized, it's shed along with your uterine lining during your period
While a woman is already pregnant, the probability of superfetation--conceiving a second child while already pregnant--is extremely low.
Raping a female who is not yet sexually fertile will not produce a pregnancy. Raping a woman who is menopausal (that is, fully menopausal, when menstruation has ceased) is highly unlikely to produce a pregnancy.
Quite apart from all of that, rape will only have an evolutionary advantage if there is a conception, the child is carried to term and said child then reaches sexual maturity and successfully reproduces. There are no evolutionary prizes for getting close--we're not talking about a game of horseshoes.
Inflicting severe injuries on a woman during rape will reduce the probability of a woman carrying the child to term, delivering the child and surviing to rear the child to sexual maturity. Killing the woman's mate, and especially killing the woman's companions will drastically reduce the probability of the woman carrying the child to term and then successfully raising the child to sexual maturity. These are important considerations in the question of evolutionary advantage in that even using Thomas' skewed math, the effect would have had to have occurred within the last 1400 years. Fourteen hundred years ago, if the woman's mate and companions were killed during the incident which culminated in the rape means there would be a low probability of the child being carried to term and raised to sexual maturity.
There have been a lot of snap answers here, such as your and Thomas' claims about the math, which appear to have entailed very little thought, very little reflection. Tediously, i will point out once again that i am not saying that there is no evolutionary advantage to rape. I'm pointing out that those who claim there is have not made their case.