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.
