Posted in Psychology & Medicine

Kuru

European explorers who visited the island of Papua New Guinea in the 1950’s noticed that the Fore tribe suffered from a strange disease. The patient would initially have headaches, joint pains and tremors. They then show signs of weakness and are unable to stand.  The shaking of limbs, a classic symptom of the disease, becomes progressively worse as the disease progresses (“kuru” is a Fore word for “to shake”). In the late stages, the patient shows other neurological symptoms such as uncontrollable laughter and emotional instability. By this point, their tremors and ataxia (lack of coordination) is so severe that they cannot sit without support. They may also suffer from inability to speak or swallow, become unresponsive to their surroundings, develop ulcers on the skin and become incontinent (cannot hold urine/faeces). Within 3 months to 2 years after the symptoms develop, the patient dies.

Kuru is exclusive to the Fore tribe and medical researchers were puzzled by the nature of this disease. It is incurable and takes more than 10 years to develop (from the time of infection). In 1961, Dr Michael Alpers discovered that kuru was spread due to a certain cultural behaviour within the tribe – cannibalism. The Fore tribe had a tradition of eating the corpse of a deceased tribe member at the funeral as to return their life force back in to the tribe. Of course, this involved the consumption of the brain as well.

It was discovered that kuru is caused by a strange pathogen known as a prion. Prions are misfolded pieces of proteins that cause disease by converting the body’s proteins into “wrong” proteins. These new prions then convert more proteins until the body is filled with deposits of such proteins. Prions mainly affect the brain and cause spongiform encephalopathy – meaning that the brain becomes sponge-like and full of holes. The most famous example of prion disease is mad cow disease.

After colonists took over Papua New Guinea, cannibalism was banned and kuru faded away. This was proof that cannibalism was what spread the prion from one victim to another. It was also discovered that women and children had a higher incidence as men would have priority in choosing what part of the body to eat first. As with lions, the men always chose muscles first and women and children would often finish the organs such as the brain. As prions are indestructible, it cannot be treated, cured or prevented (other than not eating brains). It also means that it transmits perfectly from a dead patient to an unsuspecting victim who is feasting on the infected brain.

A disease that causes the brain to disintegrate, causing limb shaking and inability to walk, spread by the ingestion of brains. Is it possible that zombies are caused by eating brains and not the other way around?

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Posted in Science & Nature

Praying Mantis

The praying mantis is sometimes considered a symbol of ultimate female empowerment. After mating, it has been observed that the female would immediately proceed to kill the male she just mated with and eat his corpse, head first.
However, one thing that is less known is that this act – known as sexual cannibalism – occurs almost exclusively in captivity. This is because in the wild, a male runs off quickly after mating to avoid a grim fate. The female, with a massive appetite after the tiring act of copulation, looks for a source of nutrients to upkeep her pregnancy. As in a captive environment the male cannot run far and the female cannot hunt easily, she opts to eat the male as this is more beneficial for her. Furthermore, as mantises have very sharp vision, it is highly likely that the observing scientists (giant, towering figures dressed in white) will intimidate the female mantis. The anxiety caused by the observation would thus make the female act more violently.

The theory that lab intervention caused sexual cannibalism was proven when mantises stopped cannibalising after being fed ad libitum (until they were full). In fact, the female would carefully observe the courtship dance of the male and decide whether he is worthy of mating. This courtship dance also has the effect of switching the female’s priorities from feeding to mating.

It has also been suggested that females may choose to eat the males they do not deem worthy (before mating), or that the males are sacrificing themselves to improve the chance of fertilisation. This is supported by evidence of decapitated male mantises copulating more vigorously and mounting the female for much longer periods. 

In other words, male submissiveness can be a factor in reproductive success.