Mad
Cow disease
and other prion news
Were the Neanderthals
cannibals?
Kinfood
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The first known case of disease spreading by cannibalism in humans happened in the 1950s in the New Guinea highlands. Tribes of isolated natives were dying from Kuru, a disease with symptoms including loss of motor control and dementia. Infectious agents called prions, also responsible for Mad Cow disease, cause Kuru. Prions are believed to be an aberrant form of a protein, and unlike bacteria and viruses, contain no nucleic acids, making them pernicious and also a scientific surprise.
When scientists descended on the highlands to search for the cause of Kuru, they found that tribe members ground up the brains of deceased relatives during a religious ceremony and ate them in a soup. Once scientists warned the natives against this practice, the disease dropped nearly out of sight.
Pfennig thinks the avoidance of cannibalism can be taken even further; he feels animals should refrain from eating any species closely related to them. Eating organisms that are genetically farthest from oneself provides the least disease risk. Following this, the best possible diet for disease avoidance in humans should be plants.
“You could say that I am making an argument for vegetarians, but that is not necessarily so,” Pfennig says. “There is another really important factor. If you were extremely hungry and I gave you a choice between a steak and a salad, which would you go for?”
Food isn’t only about disease risk; it is also about nutrition. And here lies the contradiction, because cannibalism provides the perfect nutrients.
“Eating your own species allows you to obtain the necessary nutrients for your own growth and maintenance, and they have already pre-packaged those materials for you in the proper proportions,” Pfennig says. “This is one of the paradoxes of why cannibalism isn’t more common.”
Pfennig says the optimal diet is one somewhere in the middle, close enough to one’s own species so that the individual garners sufficient nutrients, but far enough away so the disease risk is low.
“Experiments have been done that show that organisms don’t prefer to eat their own kind, they don’t prefer to eat things that are really different, but they prefer to eat things that are pretty intermediate,” Pfennig says. “The highest fitness return should be on the intermediate diet choice.”
Pfennig’s new research continues in the direction of diseases. He wants to investigate whether diseases can pass more easily through populations that are genetically similar to one another. As an example, Pfennig points to the decimation of New World populations, thought to be highly inbred and genetically homogenous, when faced with Old World diseases for the first time.
But he has answered his initial question about why most species tend to shy away from eating their own kind. Not only would it turn the stomach of most people to gnaw on a forearm, but it would be a health risk, too.
Article
by Brady
Huggett
© Copyright 2000 Endeavors
magazine, The University of North Carolina at Chapel Hill. All rights
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