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According to the reigning competition-driven model of evolution, selfish behaviors that maximize an organism’s reproductive potential offer a fitness advantage over self-sacrificing behaviors—rendering unselfish behavior for the sake of others a mystery that requires extra explanation. Evolution, Games, and God addresses this conundrum by exploring how cooperation, working alongside mutation and natural selection, plays a critical role in populations from microbes to human societies. Inheriting a tendency to cooperate, argue the contributors to this book, may be as beneficial as the self-preserving instincts usually thought to be decisive in evolutionary dynamics.
Assembling experts in mathematical biology, history of science, psychology, philosophy, and theology, Martin Nowak and Sarah Coakley take an interdisciplinary approach to the terms “cooperation” and “altruism.” Using game theory, the authors elucidate mechanisms by which cooperation—a form of working together in which one individual benefits at the cost of another—arises through natural selection. They then examine altruism—cooperation which includes the sometimes conscious choice to act sacrificially for the collective good—as a key concept in scientific attempts to explain the origins of morality. Discoveries in cooperation go beyond the spread of genes in a population to include the spread of cultural transformations such as languages, ethics, and religious systems of meaning.
The authors resist the presumption that theology and evolutionary theory are inevitably at odds. Rather, in rationally presenting a number of theological interpretations of the phenomena of cooperation and altruism, they find evolutionary explanation and theology to be strongly compatible.
Chapter 4: Five Rules for the Evolution of Cooperation
Evolution is based on a fierce competition between individuals and should therefore only reward selfish behavior. Every gene, every cell and every organism should be designed to promote its own evolutionary success at the expense of its competitors. Yet we observe cooperation on many levels of biological organization. Genes cooperate in genomes. Chromosomes cooperate in eukaryotic cells. Cells cooperate in multi-cellular organisms. There are many examples for cooperation among animals. Humans are the champions of cooperation: from hunter gatherer societies to nation states, cooperation is the decisive organizing principle of human society. No other life form on earth is engaged in the same complex games of cooperation and defection. The question how natural selection can lead to cooperative behavior has fascinated evolutionary biologists for several decades.
A cooperator is someone who pays a cost, c, for another individual to receive a benefit, b. A defector has no cost and does not deal out benefits. Cost and benefit are measured in terms of fitness. Reproduction can be genetic or cultural. In any mixed population, defectors have a higher average fitness than cooperators (Figure 4.1). Therefore, selection acts to increase the relative abundance of defectors. After some time co-operators vanish from the population. Remarkably, however, a population of only cooperators has the highest average fitness, while a population of only defectors has the lowest. Thus, natural selection constantly reduces the average fitness of the population. Fisher’s fundamental theorem, which states that average fitness increases under constant selection, does not apply here because selection is frequency dependent: the fitness of individuals depends on the frequency (=relative abundance) of cooperators in the population. We see that natural selection in well-mixed populations needs help for establishing cooperation.
Kin Selection
When J.ºB.ºS. Haldane remarked, “I will jump into the river to save two brothers or eight cousins,” he anticipated what became later known as Hamilton’s rule (Hamilton 1964). The ingenious idea is that natural selection can favor cooperation if the donor and the recipient of an altruistic act are genetic relatives. More precisely, Hamilton’s rule states that the coefficient of relatedness, r, must exceed the cost-to-benefit ratio of the altruistic act:
r > c/b (1)
Relatedness is defined as the probability of sharing a gene. The probability that two brothers share the same gene by descent is 1/2, while the same probability for cousins is 1/8. Hamilton’s theory became widely known as “kin selection” or “inclusive fitness” (Grafen 1985; Taylor 1992; Queller 1992; Frank 1998; West, Pen, and Griffin 2002; Foster, Wenseleers, and Ratnieks 2006). When evaluating the fitness of the behavior induced by a certain gene it is important to include the behavior’s effect on kin who might carry the same gene. Therefore, the “extended phenotype” of cooperative behavior is the consequence of “selfish genes” (Dawkins 1976; Wilson 1975).
Overview
According to the reigning competition-driven model of evolution, selfish behaviors that maximize an organism’s reproductive potential offer a fitness advantage over self-sacrificing behaviors—rendering unselfish behavior for the sake of others a mystery that requires extra explanation. Evolution, Games, and God addresses this conundrum by exploring how cooperation, working alongside mutation and natural selection, plays a critical role in populations from microbes to human societies. Inheriting a tendency to ...