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Sperm invading womb

Conflict between the sexes over reproductive interests can drive rapid evolution of reproductive traits and promote speciation. Here we show that inter-species mating between Caenorhabditis nematodes sterilizes maternal individuals. The principal effectors of male-induced harm are sperm cells, which induce sterility and shorten lifespan by displacing conspecific sperm, invading the ovary, and sometimes breaching the gonad to infiltrate other tissues. This sperm-mediated harm is pervasive across species, but idiosyncrasies in its magnitude implicate both independent histories of sexually antagonistic coevolution within species and differences in reproductive mode self-fertilizing hermaphrodites versus females in determining its severity. Consistent with this conclusion, in androdioecious species the hermaphrodites are more vulnerable, the males more benign, or both. Patterns of assortative mating and a low incidence of invasive sperm occurring with conspecific mating are indicative of ongoing intra-specific sexual conflict that results in inter-species reproductive incompatibility.
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The Unwanted Houseguest

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In the battle of the sexes, there are the formal rules -- the rich variety of variously heeded laws and customs by which each society tries to constrain reproductive behavior. Then there are the other rules, often in conflict with the first, which govern love and desire and the delicate games men and women play with one another. If these other rules, the ones built into human nature, could be specified, they would not tell what is right -- that is the province of the first set of rules -- but they would help understanding of how human sexual and social behavior have evolved. Primatologists, who study the group of mammals that includes monkeys, apes and people, have developed some surprising ideas about the nature of the human mating system, suggesting that women may not be as faithful as their mates may suppose. And some biologists think that the deceits of the mating game may even be reflected in the hapless spermatozoon. People's two closest evolutionary cousins, gorillas and chimpanzees, have evolved two very different patterns of sexual behavior and social organization. Gorillas practice ''female defense polygyny,'' with one male guarding a harem of females, whereas chimpanzees band together in multimale, multifemale groups.
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Tara's Breeding

This review attempts to summarize the current knowledge on uterine inflammatory response after mating in horses, pigs and cattle. Post-mating endometritis has been extensively studied in horses as it has been considered to cause infertility. The inflammation is known to occur also in cattle, but it has not been investigated to a similar extent.
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The oldest historical reference I could find to humans using birth control is a French cave painting estimated to be 12,, years old that purports to show a man wearing some sort of condom-like device, although to me it merely looks like a guy with a pointed dick trying to fuck a wildebeest. To each their own, I suppose. Different strokes and all that. Whatever gets you through the night. There is a veritable cornucopia, plethora, bumper crop, mother lode, or honeypot—take your pick—of information online alleging that for millennia, human females have attempted to avoid becoming totes preggers.
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