The same core theories that are used to understand cooperation in humans and other animals can also be applied to microbes. ~ English evolutionary biologist Kevin Foster
Social assistance is so common as to be unremarkable. Yet cooperation has been a conceptual conundrum to evolutionary biologists. Whereas selfishness seemed to them sane, altruism posited a puzzle.
The widespread phenomenon of organisms paying costs to help others (altruism) is a long-standing paradox in biology. ~ English evolutionary biologist Patrick Kennedy et al
The idea that altruism needs theoretical underpinning is ridiculous. Given our own experiences of sociality, occasional beneficence should be no mystery.
Darwin grappled to explain altruism in light of his “survival of the fittest” credo. Darwin’s answer – group selection – was honed by Ronald Fisher in the 1910s to the idea that family matters. English evolutionary biologist John Maynard Smith coined the term kin selection in 1964.
By kin selection I mean the evolution of characteristics which favour the survival of close relatives of the affected individual. ~ John Maynard Smith
English evolutionary biologist W.D. Hamilton gave kin selection a quantitative treatment in 1964, creating a formula for when help might be given.
rb–c ▫ 0
r is the coefficient of relatedness, expressing how closely related individuals are. b is the benefit of help. c is the cost to the caregiver. According to the formula, altruism happens if the benefit by genetic relatedness exceeds the cost.
Kin selection is relevant not just to driving altruism but also to limiting selfish behavior and conflicts. ~ Katherine Geist et al
Hamilton explained the seeming self-sacrifice of eusocial bee, wasp, and ant colonies by genetic relation: a single colony being all in the family. Other relatedness behaviors were explained as a balancing act of resource allocation that may tip in favor of selfishness.
Familial conflict provides multiple examples of the strangeness inherent in kin selection, including weaning, siblicidal behavior, and infanticide. Burying beetles are caring parents who practice infanticide to optimize survival prospects for the remaining brood: calculated concern.
Juvenile great egrets often kill younger nestlings while parents looking on. An egret chick may peck a sibling, stab it with its beak, or push it out of the nest.
A closely related bird, great blue herons, seldom suffer such nestling trauma. An explanation can be found in parental feeding habits. Egrets bring their young small boluses of fish, just enough for one chick at a time. An aggressive chick might monopolize the food supply by getting rid of its nest mates. In contrast, great blue herons bring a whole fish to the nest: more than a chick can eat. Sibling rivalry does not confer the same apparent advantage.
Conflict between parents and offspring is ubiquitous with weaning: whereas the offspring’s self-interest is nourishment, a mother’s self-interest may be to conserve herself for the next offspring. This motivation neatly falls within Hamilton’s cost-benefit formula. But it is not necessarily so. The alternate and more plausible explanation is that mom is fatigued from the chore of taking care of a youngling which can now – and must learn to – take care of itself. Mom knows that she has done all that she should. In other words: tough love.
Relatedness is expected to decrease conflict, so it is interesting that kin interactions nevertheless drive rapid evolution, consistent with an evolutionary arms race. One reason may be the constancy of the conflict. ~ Katherine Geist et al
Plants also have kin selection conflicts. A seed plant must decide how much endosperm to allocate to an embryo. This is a difficult optimization exercise in resource allocation: providing sufficient endosperm to improve the odds of a seedling surviving versus giving more than enough and thereby lessening the number of seeds that can be produced.
Seed plants show rapid spurts of adaptation related to endosperm production (before genetic changes settle down). The same optimization process applies to seed coating and other aspects of maternally bundling offspring for germination success. Somehow plants get the feedback they need to produce ideal seeds for a targeted environment.
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The idea of inclusive fitness is a broader umbrella of kin selection. Whereas kin selection requires the perception of being related, the woollier notion of inclusive fitness is a social model of selection, which theoretically can encompass reciprocal altruism, such as with vampire bat blood-sharing, or other such acts common in many animal species.
From a sociobiologist’s perspective, reciprocal altruism has the flavor of an instant oxymoron, resolved only by time: giving by calculation of future payback. That is a narrow view of cunning. The natural world is not always so shrewd, as the innumerable tales of animal friendship testify. Emotional satisfaction also encompasses benefaction.
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The fundamental units of natural selection, the basic things that survive or fail to survive, are called replicators. DNA molecules are replicators. They generally gang together into large communal survival machines. ~ Richard Dawkins
Despite ostensibly getting beyond family ties, the supposed calculation behind inclusive fitness fits within the gene-centric nonsense of Richard Dawkins. That worldview of monomaniacal selfishness, which may be momentarily disguised for a deal involving reciprocity, boils down to an unrelenting drive for ersatz immortality via genetic replication. It is sophistry, as our own diversities of motivations show. Further, there is no evidence that other life forms are so single-minded. To the contrary: vertebrates typically exhibit the same emotive and motivational ranges that people have. (We have a harder time discovering how invertebrates feel, but there is no reason to think that they are much different.)
From an evolutionary perspective, it makes sense that occasional assistance is the norm in unforgiving habitats: altruism as a matter of course when help may be a matter of life or death. The black harvester ants that inhabit the Mojave and Sonoran deserts illustrate. These ants thrive in colonies numbering tens of thousands. Each day they walk a single route to collect seeds. If an ant becomes ensnared in a spider web, cohorts rescue it, clean the silk from its body, and carry the ant back to the nest if it is injured. The foraging ants then tear the web apart to remove the hazard, taking hours to do so if necessary. Each life matters.
Individuals help more to promote their own success, not just the success of family members. Even though it seems that helping behaviour is altruistic, self-interest is also in play. ~ English zoologist Charlie Cornwallis
Rather than fly off to start their lives on their own, young adult birds often stay and help rear younger siblings. They do so to learn parenting techniques, and perhaps to inherit the nest and attendant territory, which can be a rich reward.
In birds, mammals, bees and wasps, cooperation is more common in unpredictable or harsh environments. ~ English zoologist Andrew Higginson et al