I have often wondered what evolutionary advantage there could possibly be for pregnant woman to have "morning sickness" during pregnancy. Of course the religionists would say that the nausea experienced by most women during certain times during their pregnancy was part of the curse laid on womankind by God because Eve listened to a talking snake and ate a forbidden fruit. I have recently found a much more feasible and scientific explanation for this phenomenon. (Most of the quotes in this article can be found in Steven Pinker's marvelous book "How the Mind Works")
The usual explanation is that pregnancy sickness is a side effect of an imbalance of hormones. My question has always been, why on earth should a natural event such as pregnancy be plagued by hormonal imbalances? Freud had an even more ridiculous explanation: "that pregnancy sickness represents the woman's loathing of her husband and her unconscious desire to abort the foetus orally"(!)
Biologist Margie Profet has developed a much more plausible theory than the one suggested by the religionists, conventional medicine or Freud. It seems obvious that if pregnancy sickness evolved in humans, that there has to be an evolutionary advantage to this phenomenon. After all vomiting surely would lower nutrition to the unborn foetus. So what possible advantage could there be to the foetus?
Nausea and vomiting is a protection against ingesting toxins. The poisonous food is eliminated from the stomach before it can do harm and we avoid foods causing nausea in future. It is an established fact that, because plants do not particularly want to be eaten, they have evolved ways of protecting themselves. Most plants have evolved a number of toxins in their tissues, such as insecticides, insect repellents, irritants, paralytics and poisons. Herbivores and omnivores in their turn evolved measures to counteract these toxins such as, for instance, a liver function that detoxifies poisons. (Sometimes the liver gets overwhelmed by chronic and excessive intake of poisons such as alcohol). The problem may be that the developing foetus at an early stage may not have developed these counter-measures yet, and would therefore be vulnerable.
To prove her theory, Profet looked at hundreds of studies that support her theory. This is what she found:
"1. Plant toxins in dosages that adults tolerate, can cause birth defects and even induce abortion when ingested by pregnant women.
2. Pregnancy sickness usually begins when the embryo's organ systems are being developed and the embryo is most vulnerable to teratogens (birth defect-inducing agents) but is growing slowly and has only a modest need for nutrients.
3. Pregnancy sickness wanes at the stage when the embryo's organs are nearly completely formed and the biggest need is for nutrients to promote growth.
4.Women with pregnancy sickness avoid bitter, pungent, highly flavoured and novel foods, which are in fact the ones most likely to contain toxins.
5. Women's sense of smell becomes hypersensitive during the period of pregnancy sickness and less sensitive thereafter.
6. Foraging peoples (including our ancestors) are at even greater risk of ingesting plant poisons, because they eat wild plants rather than domesticated crops bred for their palatibility.
7. Pregnancy sickness is universal across human cultures.
8. Women with more severe pregnancy sickness are less likely to miscarry.
9. Women with more severe pregnancy sickness are less likely to produce babies with birth defects.
I know that this article will not necessarily make pregnant ladies suffering from pregnancy sickness much happier with their lot, but at least they will now know that the whole nauseating experience was beneficial to their unborn baby and had nothing to do with Eve being seduced by a talking snake!
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