feelings was: to get organisms to approach things or avoid things that are, respectively, good for them or bad for them. Nutrients, for example, keep organisms alive, so natural selection favored genes that gave organisms feelings that led them to approach things containing nutrients—that is, food. (You may be familiar with such feelings.) Things that harm or kill organisms, in contrast, are best avoided, so natural selection gave organisms feelings that inclined them to avoid such things—feelings of aversion. To approach or to avoid is the most elemental behavioral decision there is, and
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