Duality Of Stochasticity And Natural Selection Shape The Ecology-driven Pattern Of Social Interactions: The Fall Of Hamilton's Rule

Both competition and cooperation are pervasive at all levels of biological organization. Traditionally, the theory of evolution, understood as “red in tooth and claw” is challenged by the mere existence of cooperation. As a plausible explanation of this conundrum, Hamilton’s rule has dominated sociobiology for 50 years, but its genetic component (relatedness) is increasingly questioned. On the other hand, there is no doubt that social interactions are regulated by ecological (cost-benefit) factors. Hamilton’s rule, like Darwin’s theory, implicitly assumes a stable environment. Stable environments favor selfish individuals that are selected to maximize their fitness. Hamilton’s rule allegedly explains the paradox of altruism, that selfish individuals forego their own reproductive opportunities to help close kin to reproduce. Kin selection/inclusive fitness was Hamilton’s explanation for this conundrum. But abiotic and biotic environments are not stable, but variable, often unpredictable. Particularly, biotic environments with their mani fo ld conf l ic ts, Red Queen coevolutionary arms races, and densityand frequency-dependence of fitness have often chaotic dynamics. Environmental stochasticity, resulting in uncertain, unpredictable reproductive success, changes fundamentally the rules for the “gamble of life”. A cybernetic model of evolution revealed the duality of stochasticity and natural selection at input and output levels of the evolutionary Black Box, resulting in multilevel selection of social behavior (Heininger, 2013, 2015). From microbes to mammals, cooperation is selected-for in harsh, uncertain and unpredictable environments. In stochastic environments, cooperation trades individual fitness maximization for less variability and greater reliability of evolutionary outcomes. Thus, the evolution of cooperation is a bet-hedging (risk spreading) strategy of risk-averse individuals. The biological default setting of individuals is neither selfish nor cooperative but ecologically context-dependent and dynamic. Competition and cooperation are threshold traits of nonlinear complex systems on a continuum of ecological variables. The frequent kin structure of communities is not the predominant reason for cooperation/altruism but the result of limited dispersal. Limited dispersal and the evolution of cooperation share environmental stochasticity as common cause resulting in spurious relationships. The environmental conditions that favor cooperativity discourage dispersal and promote philopatry, thus shaping the preferential kinship structure of cooperative communities. Under more adverse ecological conditions, kin competition can strongly antagonize the benefits of kin cooperation and inhibit the evolution of cooperation in viscous populations. Not kinship but context-dependent, pleiotropic processes shape the dynamic sociobiological behavior of populations. The ecological conditions and genetic “fossil record” of social behavior in both prokaryotic and eukaryotic microbes hold the key to understand the evolutionary present of cooperation in higher taxa. In microbes, cooperative behavior is induced by adverse conditions, particularly starvation, leading to social aggregations with the formation of complex patterns such as fruiting bodies and biofilms. In colonies of metabolically stressed clonal cells the competition for scarce resources is decided by a fair lottery. Experiments with bacteria and social amoeba suggest that cell fate ‘decisions’ (either survival as spores or cell death whose remains fuel the metamorphosis of spores) are stochastic, and moreover that these ‘decisions’ are controlled by genetically-encoded probabilities that are evolvable. Behind the “veil of ignorance”, the competitors are not “aware” of their relative position in the competitive hierarchy. This hierarchy is determined stochastically through a variety of cellular processes with inherent noise that render the cel ls heterogeneous and the lotteries fair. The vast majority of cooperative systems are characterized by dominance hierarchies with asymmetric conflicts between dominants and subordinates over limited reproductive opportunities. Eusocial societies, the Holy Grail of kin selection theory, are despotic Orwellian societies that only serve the reproductive needs of selfish Big Sisters and Brothers that for this purpose enslave, police, and suppress their worker castes by aggression and WebmedCentral > Original Articles Page 2 of 264 WMC004804 Downloaded from http://www.webmedcentral. com on 30-Mar-2015, 08:50:53 AM chemical agents. In this respect they resemble a unitary metazoan organism with its reproductive monopoly of the germline. Punishment allows the evolution of cooperation (or anything else) in sizable groups; thus neither altruism nor inclusive fitness gains are behaviorally or causally involved in these despotic systems. Intriguingly, queen pheromones are even able to suppress reproductive activity across species boundaries e.g. from honeybees to fruit flies. The existence of this oppressive system clearly argues against the role of inclusive fitness in the evolution of eusociality. Nestmate recognition, the eusocial version of the immune system and histocompatibility complex, has the function to ensure the reproductive monopoly. Within my alternative conceptual framework of colony fitness a joint genetic-physiological-behavioralecological hypothesis of eusociality in insects is presented. In stochastic environments, reproductive success is unpredictable and highly variable. In taxa without parental brood care, particularly insects, survivorship to reproductive maturity is extremely low. Even in eusocial insects with independent colony foundation, the vast majority of attempts to establish a colony will fail. The extent to which immediate gains are preferred over future rewards is known as future discounting. Individuals who grow up in environments where resources are scarce, competition is intense, and mortality is high should discount the future with its uncertain benefits more heavily than individuals who grow up in abundant, supportive, long-lived habitats. On the other hand, an uncertain, unpredictable environment selects for evolutionary gambling, and either conservative or diversifying bet-hedging as individualor population-level insurance to individual risk. The deterministic Hamilton’s rule is hardly compatible with the stochasticity of reproductive success in uncertain, unpredictable environments. If the basic assumptions of kin selection/inclusive fitness theory would be right, eusociality should have evolved in ( i) less adverse environments with less unpredictable reproductive success, and (ii) in taxa with more predictable reproductive success and, hence, less uncertain inclusive fitness benefits. The insight that cooperation is a selected-for trait in stochastic environments unifies the so-far distinct concepts of cooperation, mutualism, symbiosis and cooperation in mating systems. Cooperation emerges as a self-organized behavior of complex systems. Phenomena such as swarm-behavior and -intelligence and division of labor emerge from the interplay of both stochastic and deterministic forces, generating order from disorder through self-organization. Responding to the uncertainties of lotteries with insurance policies, populations engage in nest/burrow building, social contracts with assured fitness returns and social queuing. Via the law of large numbers evolution generated a form of automatic biological insurance against idiosyncratic risk. From a systems biology perspective Hamilton’s rule is simplistic, biased by observation selection, static, and parochial (ignoring the world outside its limited scope, i.e., both the huge majority of cooperative behaviors targeted to nonkin and to other species and being blind to epistemological inputs e.g. from complexity theory and neurobiology). Hamilton’s rule was (and many mathematical models still are) shaped by an egalitarian worldview in which autonomous individuals “decide” to forego their reproduction and help their kin to ensure the representation of their genes in the next generation. In nature, however, the vast majority of cooperative systems are characterized by dominance hierarchies with asymmetric conflicts. The “decision” of subordinates to help is not self-determined but enforced by despotic dominants and the prevailing environmental conditions that limit the subordinates’ options for independent reproduction. In a world of nonlinear biological processes and social interactions, complex emergent behavior, and probabilistic theories, Hamilton’s linear and deterministic rule is a plausibility-based anachronism (one of Gould and Lewontin’s “just-so stories”) rooted in Newtonian thinking. Increasingly, “expanded” definitions of altruism and indirect fitness have been used to rescue the concept. The sociobiological definition of altruism, as one of an outcome, does not say how this outcome has been achieved. In sociobiological parlance, definitions such as fitness transfer by force, “enforced altruism”, as a result of mere luck “coin-flipping altruism”, or the mutual exchange of commodities “reciprocal altruism”, pervert the common sense definition of altruism. In its last consequence, kin selection theory is a fascistoid concept, emphasizing the cohesive value of genetic homogeneity for a population tied together by parochial altruism. Parochial altruism promotes group conflict and may coevolve with warfare. On the other hand, mutualism causes partners to become increasingly dependent on each other as a basis for peaceful coexistence in societies.