Sunday, June 29, 2008

Good Bad Adaptations

Here are some quirks in the design of the human body/mind which may turn out to be adaptations:

“Morning sickness” is the common term for nausea and vomiting in early human pregnancy (NVP). Recent interest in why NVP occurs-that is, in the evolutionary costs and benefits of NVP-has spurred the development of two alternative hypotheses. The “prophylaxis,” or “maternal and embryonic protection,” hypothesis suggests that NVP serves a beneficial function by expelling foods that may contain harmful toxins and microorganisms and triggering aversions to such foods throughout pregnancy. The alternative “by-product” hypothesis suggests that NVP is a nonfunctional by-product of conflict-over resource allocation-between the pregnant woman and the embryo. The critical predictions of the prophylaxis hypothesis have been developed and tested, whereas the by-product hypothesis has not been subjected to similar scrutiny. To address this gap, we developed a graphical model and used it to derive predictions from the by-product hypothesis under two different assumptions, namely, that NVP is either (i) a by-product of current conflict between a pregnant woman and an embryo or (ii) a by-product of honest signals of viability produced by the embryo. Neither version of the by-product hypothesis is fully consistent with available data. By contrast, the timing of NVP, its variation among societies, and associated patterns of food cravings and aversions are consistent with the prophylaxis hypothesis.

On Depression:

I recently wrote a paper for my Psychology class about Depression, allow me to quote it:

Why does depression exist? Is it simply a genetic disorder, or is it possible that it is so common because it helps individuals survive in some way? Charles Darwin said, “…Pain or suffering of any kind, if long continued, causes depression and lessens the power of action; yet is well adapted to make a creature guard itself against any great or sudden evil.” [1] Today Psychologists are following suggestions like his in order to find out why so many people suffer from depression. Some believe that after a series of defeats it would be useful to an organism’s survival to adopt a pessimistic attitude and act conservatively[2].

[1] p.89, “The Life and Letters of Charles Darwin” by Charles and Francis Darwin. Accessed at:
[2] Nesse RM, et. al “Is Depression an Adaptation?” Arch Gen Psychiatry 2000; 57:14-20
Accessed at:

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