 Since the beginning of time, pregnant women have been known to suffer nausea and vomiting during pregnancy. The term morning sickness is actually misleading, since women can feel sick all day long. And sometimes it can get so serious women have to be hospitalized. Researchers at Harvard's Brigham and Women's Hospital found that saturated fat seemed to be a primary dietary risk factor for severe sickness. Five times the odds reached 15 grams intake of saturated fat, like a quarter-pound cheeseburger's worth. The recent saturated fat intake, maybe such a strong risk factor, could be through its effect on estrogen as saturated fat has been shown to increase circulating levels of estrogen. Why would we evolve such a negative reaction to saturated fat? Why would we evolve to get sick at all? Pregnancy sickness is a universal phenomenon with nausea and vomiting affecting 70 to 85% of all pregnant women. If you include food aversions in the definition, then the incidence is more like 100%. Because pregnancy sickness is such a common phenomenon, one must question, why is this so? Is there a purpose for such a potentially devastating condition? Well, in the past, pregnancy sickness was dismissed, as all in just in women's heads. But recent studies have reconsidered pregnancy sickness as an embryo-protective mechanism, an evolutionary adaptation to protect the baby. Protect the baby from what? Maybe from meat. Meat is the principal source of pathogens for humans. Meat is also the most common type of food avoided by pregnant women. So the development of an aversion to meat during pregnancy could be protective, as meat may have toxins that are mutagenic, carcinogenic, and tarratogenic, meaning birth defect causing. Tainted meat may also be contaminated by pathogens, and pregnancy is a time of relative immunosuppression. Normally we can fend off most meat pathogens. However, by design, pregnant women are immunosuppressed to not reject the developing embryo, since half the baby from the father's side is foreign. So maybe morning sickness evolved as a way to get us to stay away from meat during this vulnerable time. This would be consistent with a profound over-representation of taboos against meat-eating during pregnancy in sample societies around the world. If this theory is true, then we should be able to make five predictions. If nausea-invomiting pregnancy is there to be protective, then women who have it should have better pregnancy outcomes. And indeed, women who experience nausea-invomiting are significantly less likely to miscarry or suffer a stillbirth. Prediction number two would be that the triggering foods contain things that could be particularly harmful to the baby, and indeed, of all food types, animal protein, including meat, poultry, eggs, and seafood is the most dangerous. Meat is the source of a wide range of pathogens that pose a grave threat to pregnant women and their developing babies. Nausea-invomiting pregnancy should also coincide with when the embryo is most vulnerable. That's between, like, you know, weeks 5 and 15 when all the critical organ structures are being formed, which is right when nausea-invomiting is peaking, which is right when pregnant women find meats, fish, poultry, and eggs most aversive. And finally, if this theory is true, one would expect a lower frequency of morning sickness among plant-based populations. And yes, the few societies where you don't see such morning sickness problems are the ones that tend to have only plants as dietary staples rather than meat.