One of the worst parts of being pregnant […] is what is commonly referred to as morning sickness.
This term for the nausea and vomiting accompanying pregnancy is something of a misnomer, actually, since such gastrointestinal issues certainly aren’t limited to the morning hours. Rather, for those women who do get green around the gills (and not all do; more on that later) sudden bouts of toilet-hugging can happen morning, noon and night. […]
Why, if it is indeed an evolutionary adaptation, does pregnancy sickness not occur in all (or at least, almost all) pregnant women? […]
So what does Gallup say is the real culprit behind nausea and vomiting in early pregnancy? Semen. More specifically, unfamiliar semen.
Gallup’s evolutionary reinterpretation of pregnancy sickness is quite new—so new, in fact, that it hasn’t been put to a test. But at the 2012 meeting of the Northeastern Evolutionary Psychology Society in Plymouth, N.H., he and graduate student Jeremy Atkinson laid out a set of explicit predictions that, if borne out by data, would support their model and may lead scholarship away from the traditional embryo-protection account.
First, the authors predict that the intensity of pregnancy sickness should be directly proportional to the frequency of insemination by the child’s father. “Risk factors for morning sickness,” they reason, “should include condom use, infrequent insemination, and not being in a committed relationship.” In fact, Gallup and Atkinson believe that lesbians with little (if any) previous exposure to semen who are impregnated by artificial insemination should have some of the worst cases of nausea and vomiting. Also, pregnancy sickness should wane in severity from one consecutive pregnancy to the next, but only assuming that the same man sires each successive offspring. By contrast, a change in paternity between offspring should reinstate pregnancy sickness.