An evolutionary perspective

Anorexia nervosa is a very destructive disease. If it doesn't kill you, it often makes you wish it has. It destroys you- mind, body, and spirit.

So how on Earth could anorexia serve an adaptive function? It's a deadly disease. Except that certain traits of anorexia could be adaptive, if you think of humans as hunter-gatherers, nomads collecting roots and berries and the occasional auroch.

At the risk of overgeneralizing, people with anorexia have an easier time avoiding food than other people, withstand starvation better, and are hyperactive (especially during the acute phase of illness). In a time and place where food isn't a guarantee, these things can be beneficial to the human species as a whole.

In her "Adapted to Flee Famine" hypothesis, psychologist Shan Guisinger writes that these "distinctive symptoms" of anorexia nervosa are

likely to be evolved adaptive mechanisms that facilitated ancestral nomadic foragers leaving depleted environments; genetically susceptible individuals who lose too much weight may trigger these archaic adaptations. This hypothesis accounts for the occurrence of AN-like syndromes in both humans and animals and is consistent with changes observed in the physiology, cognitions, and behavior of patients with AN.

(The entire paper is about 17 pages, but well worth the read)

A new paper out in the Annals of the New York Academy of Sciences takes an evolutionary look specifically at the overactivity aspect of this trio of symptoms. CP Arun writes

Some patients with AN exhibit overactivity that can worsen their state of malnutrition. Employing an evolutionary psychiatry line of inquiry, we propose that rigidity of thinking and overactivity are behavioral phenotypic changes in AN patients that are normal to tree-dwelling mammals, such as monkeys. Such behavior can lead to good functioning as ballet dancers and athletes but lead to certain disadvantages in other areas of modern life. The overactivity in AN, though under conscious control may be neurobehavioral and driven subconsciously by disordered cerebral neuropsychopharmacology.

Though I might debate exactly how much "conscious control" a sufferer has, seeing these traits as potentially adaptive at another time and place helps me take a little bit of the mystery out of this illness.

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lhiannanshee said...

That's an interesting idea. would have been really useful cavemen. :) Any idea what an evolutionary perspective would be on bulimia?

Alissa said...

I'm glad you posted this. This has always been my personal theory on anorexia. After reading the Ancel Keys study and experiencing first hand the neurosis caused by starvation, I have always thought that our human minds must somehow be pre-programmed to revert to strange behaviors when starved. I think about how I almost became a different person when I was starving, my weird behaviors around food and my constant thoughts about it.

I would go so far as to say that most people would experience these symptoms if they reach the point of starvation. The hyperactivity is probably due to the fact that hunter/gatherers needed extra energy to go out and look/hunt for food. The body adapts to living on very little food, so more than a little feels uncomfortable. Food is thought about constantly because we needed to constantly hunt for it in order to survive.

The only thing that doesn't fit is why anorexics keep starving when the evolutionary adaptation would have developed so that one would NOT continue to starve if food was available.

Carrie Arnold said...


I don't know about bulimia- not all diseases necessarily have an adaptive function from an evolutionary standpoint.


My theory is this: most people who are starved (whether self-imposed or not) exhibit symptoms of AN. They might not have AN, in that they can start eating on their own, but the symptoms are a dead ringer.

Kim said...

Very interesting. Thanks for the post.

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I'm a science writer, a jewelry design artist, a bookworm, a complete geek, and mom to a wonderful kitty. I am also recovering from a decade-plus battle with anorexia nervosa. I believe that complete recovery is possible, and that the first step along that path is full nutrition.

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nour·ish: (v); to sustain with food or nutriment; supply with what is necessary for life, health, and growth; to cherish, foster, keep alive; to strengthen, build up, or promote


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