Cannibalism: A Perfectly Natural History(61)
Given its essential role in fetal development, what the human placenta experiences after delivery must surely be the most precipitous fall from grace in all of Organdom. Expelled by the uterine contractions associated with childbirth, this complex and amazing structure goes from revered mammalian namesake to biohazardous “afterbirth” faster than you can scream “PUSH!”
In the vast majority of mammals, though, the newly delivered placenta serves one last purpose.
In 1930, primatologist Otto Tinklepaugh took a break from his groundbreaking study on chimpanzee vaginal plugs to coauthor an article on the birth process in captive rhesus macaques (Macaca mulatta). He noted that the monkeys, and just about every other terrestrial mammal except humans and camelids (camels, llamas, alpacas, and their relatives) consumed their own placentas after giving birth. More recently, the behavior in the animal kingdom has been studied in rodents, lagomorphs (rabbits and their kin), carnivores, primates, and most artiodactyls (hoofed mammals).
Mark Kristal is the world’s foremost authority on placentophagology, and until recently, he may have been the only expert on the topic. A SUNY Buffalo professor emeritus of psychology, Kristal’s research began more than four decades ago. His work supports the hypothesis that, since placenta-eating has been observed in such a variety of mammals, it probably evolved independently and in response to one or several survival-related problems.
Researchers initially posited that eating the placenta kept the birthing area sanitary while eliminating smells that might attract predators. The fact that chimps giving birth in the trees hung around to eat their placentas instead of simply moving off (or flinging them down on some cheetahs), suggested that a new hypothesis was needed. Answering the call, dietary researchers suggested that placentophagy replenished nutritional losses associated with late-stage pregnancy and delivery. Endocrinologists hypothesized that moms might be acquiring (and replenishing) hormones present in the afterbirth. Other researchers suggested that placentophagy sated a mother’s hunger after the delivery, or that placentophagy demonstrated the new mothers’ tendency to develop “voracious carnivorousness” after giving birth.39
Kristal wasn’t buying it, though. His skepticism for any of those proposed functions stemmed from the complete absence of any valid research on the topic. He and his colleagues set out to investigate placentophagy in non-humans experimentally—in this case, lab rats. As happens frequently, the results of their experiments supported none of the earlier hypotheses. Kristal did suggest, though, that the previously proposed functions of placentophagy might provide secondary benefits, if they existed at all.
“The main thing that we found during our studies turned out to be an opiate-enhancing property,” Kristal said. He explained that placenta consumption by new rat moms appeared to increase the effectiveness of natural pain-relieving substances (opioid peptides) produced by the body. He added that that these enhanced analgesic effects lasted throughout the birth interval between individual “kittens” in a litter—an important point since rats generally give birth to seven to ten individuals.40
Kristal also told me that the results of a second set of experiments linked afterbirth consumption (by rat moms) to a form of reward for parental care. Briefly, the central nervous system, pituitary gland, digestive tract, and other organs secrete pain-blocking peptides like endorphins, enkephalins, and dynorphins, which have been used to explain terms like “runner’s high” and “second wind,” as well as the phenomenon in which gravely wounded individuals report feeling little or no pain. Kristal’s experiments indicated that those mothers who consumed their afterbirth received enhanced benefits from these natural painkillers, essentially getting an anesthetic reward for initiating maternal behavior like cleaning their pups.
I asked Kristal how long humans had been practicing placentophagy and how widespread the practice was. “I haven’t discovered any human cultures where it’s done regularly,” he told me. “When placenta-eating is mentioned, it’s usually in the form of a taboo. You have cultures saying things like ‘Animals do it and we’re not animals, so we shouldn’t do it.’ ”
In 2010, researchers at the University of Nevada, Las Vegas, searched an ethnographic database of 179 preindustrial societies for any evidence of placenta consumption. Searching for the terms “placenta” and “afterbirth” in the electronic Human Relations Area Files (eHRAF), described as “the gold standard for cross-cultural comparative research,” they found 109 references related to the special treatment and/or disposal of placentas. The most common practice (seen in 15 percent of accounts) was disposal without burial (examples include “throwing it into a lake”), followed by “burial” (9 percent). The latter narrowly beat out my personal favorite “hanging or placing the placenta in a tree” (8 percent). What the UNLV researchers did not find was a single instance of a cultural tradition associated with the consumption of placentas by moms—or anyone else, for that matter.
Considering the ubiquitous nature of placentophagy in mammals, including chimps, our closest non-human relatives, I was surprised they were unable to find at least one culture somewhere where placentas were regularly eaten. I mentioned to Kristal that I’d run across an example of placentophagy in the Great Pharmacopoiea of 1596 (a go-to guide for many New Yorkers seeking medical advice), wherein Li Shih-chen recommended that those suffering from ch’i exhaustion (whose embarrassing symptoms included “coldness of the sexual organs with involuntary ejaculation of semen”) partake in a mixture of human milk and placental tissue.