Wednesday, February 29, 2012

Mammals and Placentophagy - And How It Pertains To Us

THEORIES WHY MAMMALS EAT THEIR PLACENTA
There are 4 main hypotheses on why a mammal would ingest its own placenta.  The first of which is that a mother undergoes a shift of food preferences toward a carnivorous diet, meaning that a mammal that is normally an herbivore will suddenly have an intense craving for meat.  The second hypothesis is that mammals are simply hungry after giving birth and the placenta provides an easy, available, nutritious meal.  Many mammals have a period of anorexia before and during their births so this is an acceptable theory.  The problem with these hypotheses lies in a study done that offered different meat choices to postpartum mammals.  During and after their births, rhesus monkeys were presented with liver, beef, and pork but 100% of the time they refused the meat and instead ate their own placentas.   A similar study was done using rats and again, all of the rats chose the placenta.  These studies suggest that the first two hypotheses are incorrect.  If it was simply a matter of obtaining food, or more specifically meat, then some of the mammals would most likely have partaken of the meats offered them.
The third hypothesis is that mammals eat their placenta in response to a specific hunger.  In this hypothesis there is an assumed metabolic or endocrine change that occurs in late pregnancy and during the birth that causes a specific nutritional or hormonal need that can be supplied only by the placenta.  The placenta is very nourishing and contains many beneficial hormones so this is also an acceptable hypothesis.  However, it was shown in a study that some virgin rats and mice will enthusiastically eat donor placenta.  This suggests that this supposed specific hunger isn’t unique to only postpartum mammals, if it exists at all.
The final hypothesis is that mothers ingest their placenta to clean up their birth site so as not to attract predators.  This makes sense, as a postpartum mammal and her new young are very vulnerable, however there are several problems with this theory.  First, and most obvious, is that the placenta is not the only part of the after birth, but it is the only part eaten.  There is also a good amount of fluid that would be very attractive to predators that is ignored by the mammal mothers.  Another is that, even mammals of unchallenged predatory species eat their placentas.  Certain primates that birth in trees could easily let their placentas drop to the ground, but instead they make sure to keep their placentas with them in the trees and spend several hours eating them.  This suggests that protecting themselves from predators is not a primary factor in placentophagy.
DOES PLACENTOPHAGY HAVE AN EVOLUTIONARY PURPOSE?
An interesting purpose of placentophagy may be on the RH factor.  The mother and baby’s blood systems are separate, but there are instances when the baby’s blood can enter the mother’s blood stream – blood transfusion, miscarriage, abortion, or certain procedures such as amniocentesis.  If a baby has an RH+ blood type and the mother has an RH- blood type then the mother can begin to make antibodies that will attack her RH+ baby’s blood.  These attacks break down the baby’s red blood cells and can cause anemia, illness, brain damage, or even death.
Today RH- women, such as myself, can receive a rhogam shot to prevent our bodies from making these dangerous antibodies.  The placenta seems to offer immunological benefits to the mother and to the baby through the breast milk.  Analysis of the placenta shows that it contains factors that if ingested would prevent the mother from producing RH antibodies.  Perhaps the use of placentophagy over thousands of years has provided the protection mothers need from forming these antibodies, or perhaps we were created with this system and knowledge already built in.   
There appear to be many different reasons why mammals practice placentophagy, each specific to its species, and related to mammals as a whole.  As more studies are done to uncover the mystery that is behind placentophagy I think we will discover a vast array of wisdom and benefits from this practice.

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