Steven Pinker -- How the Mind Works - Hampshire High Italian ...

Standard Equipment 39better than we understand any other part of the mind. There is no reasonthat reverse-engineering guided by evolutionary theory should not bringinsight about the rest of the mind. An interesting example is a new theoryof pregnancy sickness (traditionally called "morning sickness") by thebiologist Margie Profet. Many pregnant women become nauseated andavoid certain foods. Though their sickness is usually explained away as aside effect of hormones, there is no reason that hormones should inducenausea and food aversions rather than, say, hyperactivity, aggressiveness,or lust. The Freudian explanation is equally unsatisfying: that pregnancysickness represents the woman's loathing of her husband and her unconsciousdesire to abort the fetus orally.Profet predicted that pregnancy sickness should confer some benefitthat offsets the cost of lowered nutrition and productivity. Ordinarily,nausea is a protection against eating toxins: the poisonous food is ejectedfrom the stomach before it can do much harm, and our appetite for similarfoods is reduced in the future. Perhaps pregnancy sickness protectswomen against eating or digesting foods with toxins that might harm thedeveloping fetus. Your local Happy Carrot Health Food Store notwithstanding,there is nothing particularly healthy about natural foods. Yourcabbage, a Darwinian creature, has no more desire to be eaten than youdo, and since it can't very well defend itself through behavior, it resorts tochemical warfare. Most plants have evolved dozens of toxins in their tissues:insecticides, insect repellents, irritants, paralytics, poisons, andother sand to throw in herbivores' gears. Herbivores have in turn evolvedcountermeasures, such as a liver to detoxify the poisons and the tastesensation we call bitterness to deter any further desire to ingest them.But the usual defenses may not be enough to protect a tiny embryo.So far this may not sound much better than the barf-up-your-babytheory, but Profet synthesized hundreds of studies, done independentlyof each other and of her hypothesis, that support it. She meticulouslydocumented that (1) plant toxins in dosages that adults tolerate cancause birth defects and induce abortion when ingested by pregnantwomen; (2) pregnancy sickness begins at the point when the embryo'sorgan systems are being laid down and the embryo is most vulnerable toteratogens (birth defect—inducing chemicals) but is growing slowly andhas only a modest need for nutrients; (3) pregnancy sickness wanes atthe stage when the embryo's organ systems are nearly complete and itsbiggest need is for nutrients to allow it to grow; (4) women with pregnancysickness selectively avoid bitter, pungent, highly flavored, and