Today a friend told me a story she heard about a study that was done among chimpanzees in Africa. I suspect the story is apocryphal, but in a way that makes it even better.

It seems that some scientists had been studying a group of chimpanzees, and had observed behavior which in humans correlates to depression, such as eating at odd times, spending lots of time alone, and staying on the outskirts of the group. This behavior was observed in about 10% of the chimps, which happens to be near to the percentage of Americans who show symptoms of depression.

The scientists removed the depressed chimps for six months, to see how this would affect the behavior of the other 90%. It’s possible that the chimps signed a voluntary consent form for participating in such a disruptive study, but I’m not holding out much hope.

You might think that in the absence of the depressed individuals, the remaining majority would produce another 10% of depressed chimps. But apparently that’s not what actually happened.

What actually happened was this: When the scientists returned six months later, all of the non-depressed chimps were dead.

It would seem that the depressed chimps had functioned as a kind of early warning system, continually looking out for predators, tropical storms, and other threats to the group. Without that system in place, the group was doomed.

When I heard about this study, I remember thinking how great it would be for depressed people. Instead of being a problem to be fixed, they would know that their condition is a valuable asset to society, providing a critical mass of individuals uniquely suited to guarding against danger.

I figured this would make my depressed friends vey happy.

Oh no, I thought. What happens if we become a society with no depressed people? We are all doomed.

2 Responses to “10%”

  1. Manu says:

    This is very interesting, but I have to say I doubt the validity of the story. I tried hard to find sources, the only thing I found so far is that a spiritual teacher is using the story in her talks. And then it is unclear if it’s gorillas or chimps. I’m confused: http://www.tc.columbia.edu/news.htm?articleID=9738

    All other info on depression and primates is either about dominant and subordinate group members, or about animals in captivity.

  2. admin says:

    Yes, I completely agree. As I said in my post, I suspect the story is apocryphal.

    I found one of her talks on YouTube, and she definitely says chimpanzees. So either she doesn’t know the difference between chimpanzees and gorillas, or else the reporter of that article doesn’t.

    Fortunately, in either case the result is the same: No actual sentient non-humans were harmed. :-)

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