American Buddhist Net

"Human brains are not the only ones with the 5HT1A receptor. Rats also have it.

"Here's the really interesting part: the rat version is 99 percent identical to the human one. This suggests that in the evolution from the shared ancestor of rats and people (hold those creationism letters!), natural selection did not mess with the receptor much. That leave-well-enough-alone history tends to happen when the function of some trait is so important that tinkering with it evolutionarily would produce more harm than good. What kind of harm? Rodents that have a mutation causing them to lose this receptor exhibit fewer symptoms of depression when they suffer some stress, a 1998 paper reported. In other words, losing the receptor that promotes depression in response to stress is something evolution thought would be a very bad move. Ergo: depression is not something to be thrown out lightly.

"Why not? Because, argue Andrews and Thomson, depression alters thinking and behavior in beneficial ways."

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