Lee Alan Dugatkin

“If, as Hamilton’s theory suggests, helping blood relatives increases an individual’s inclusive fitness, then altruism toward kin should be particularly forthcoming from individuals in their postreproductive years. “The behaviour of a post-reproductive animal,” Hamilton argued, “may be expected to be entirely altruistic,”53 since aiding even distant relatives provides some inclusive benefits—the only fitness benefits postreproductive individuals can accrue. To test this idea, Hamilton turned to A. D. Blest’s work on saturnid moths. Blest had studied cryptic and aposematic coloration in moths. Cryptically colored species of moths use their coloration to blend into their environment and make themselves less obvious to predators. Moths that rely on aposematic coloration use their colors to warn predators that they contain noxious substances and hence would make for a bad meal. Hamilton argued that inclusive fitness thinking makes very different predictions with respect to the postreproductive behavior of individuals from cryptic versus aposematic species. In the case of cryptic coloration, if individuals live in the vicinity of kin, then, Hamilton argued, inclusive fitness theory predicts that “it is altruistic to die immediately after reproduction.”54 T o see why, imagine a postreproductive cryptic moth. If such an individual is spotted and eaten by a predator, that predator is more likely to learn what all cryptic moths look like and is then more likely to eat the nearby kin of the deceased. In such a case, the postreproductive moth’s inclusive fitness would have been higher if it had simply died after its last bout of reproduction, rather than lived and potentially drawn an experienced predator to the area containing its kin. In the case of aposematic species, intense coloration is almost always associated with a noxious taste, and so inclusive fitness thinking led Hamilton to a very different conclusion regarding postreproductive behavior. A predator who eats a postreproductive individual in an aposematic species will be less likely to eat the deceased individual’s relatives, since it will have learned that aposematically colored individuals taste terrible. A postreproductive individual in an aposematic species may raise its inclusive fitness by being eaten, and hence selection should favor life after reproduction. To Hamilton’s delight, the postreproductive life of cryptic and aposematic species matched that predicted by inclusive fitness models—with postreproductive life spans significantly shorter in cryptically colored moth species.”
― Lee Alan Dugatkin, The Altruism Equation: Seven Scientists Search for the Origins of Goodness