Actually evolution has no rules at all... the best thing we can say is that there are various ways to cheat, and that some types of cheating are hard to get away with.
Michael Ghiselin (1974, p. 41)
The Mecca of the economist lies in economic biology rather than in economic dynamics.
Alfred Marshall (1890, 1949, p. xiv)
Abstract
We argue that cooperation is instinctual. Human cooperation conferred advantages to individuals in the ancestral environment in which evolution occurred. Explanations of the evolution of cooperation for any species (human, pre-human, and non-human) have to be consistent with the biological, physiological, and environmental constraints that existed in the ancestral environment during which evolutionary selection occurred. Our explanation is consistent with: (1) the anatomical evolution of humanity; (2) the paleontological and chronological evidence; and (3) modern biology.
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Notes
A Google Scholar search of “the evolution of cooperation” produced 2.58 million hits on October 13, 2015. By contrast, a search for the term “ego” produced only 1.58 million hits; “the evolution of man” had 3.58 million; and “human psychology” had 3 million.
The experiment’s subjects were two groups of women: (1) university-level students, and (2) literally incarcerated female prisoners who cooperated at higher levels than the students.
Among the first recorded examples of cooperation contradicting theoretical priors of non-cooperation were the unexpected levels of cooperation in PD experiments at RAND in the early 1950s (see Flood 1958). In other experiments TIT-FOR-TAT dominated non-cooperative strategies in tournaments (see Axelrod 1984). “Refinements” to PD games spawned a substantial literature in an attempt to resolve unexpected levels of cooperation (see Mailath 1998). In an extensive study Camer and Casari (2009) again found surprising levels of cooperation in various experimental settings.
“Originally, this (‘refinements’) literature was driven by the hope that theorists could identify the unique “right” equilibrium. ...we now understand that that hope, in principle, could never be met. ... The refinements literature is currently out of fashion because there were too many papers in which one example suggested a minor modification of an existing refinement and no persuasive general refinement theory emerged. There is a danger that evolutionary game theory could end up like refinements.” Mailath (1998, p. 1372)
Group-selection remains a topic promoted primarily by non-biologists. The supposedly altruistic behavior of individual organisms when investigated has found net benefits to the “altruistic” individual (Wessells and Hopson 1988, p. 1048). This echoes Ghiselin’s prescient comments: “The real matter . . . is how the system is controlled. Once the point is clear it becomes obvious that supposedly altruistic individuals may act by compulsion.” (1974, p. 137) Alcock provides historical perspectives and more nuanced views of why: “Most researchers [in biology] exploring ultimate questions about behavior look first to Darwinian Theory [rather than group-selection] when producing their hypotheses” (2009, p. 22). Still, Ghiselin (2016) cautions against unscientific closed-mindedness; he worries that the parsimony of selection at the organism level “may result in real instances of it being overlooked.”
See Bowles and Gintis (2011) for a comprehensive review of the recent literature attempting a resolution between observed cooperation exceeding predicted levels.
Cooperation occurs throughout biology; multicellular organisms exist because cooperation exists within organisms at the cellular level. Above the cellular level, all sexual animals have to cooperate in reproduction. Social animals are cooperators almost of necessity. Because cooperation is so widespread in the biological world there must be benefits to the organisms involved in cooperation; otherwise, over evolutionary time, non-benefiters of cooperation would have been eliminated from the gene pool.
Khadjavi and Lange suggest that human cooperation derives from “social preferences.” Camera and Casari speculate that “other oriented preferences” rather than cognition were more likely drivers behind the surprising levels of cooperation in their experiments. These scholars may well be correct; our interest is in how and why such preferences came about.
See Iwamoto et al. (1996).
See Tamura (1989).
See Estes and Goddard (1967). The absolute size of the brain is probably less important than its size relative to its body mass. Elephants and whales have big brains, but the human brain is much larger relative to its body size.
The brains of modern humans require substantial proportions of the typical human’s nutritional intake. In utero (and in newborns) the brain takes about 87 % of a nutritionally adequate metabolic diet to maintain itself and to develop. The percentage declines as human beings age and grow larger: in a typical 5-year old the brain requires 44 % of the metabolic budget, while in adults the brain’s metabolic demands fall to 25 %. The decline in the percentage of the nutrition taken by the brain is a result of a larger body size; bigger bodies demand more nutrients to move and sustain them. See Leonard et al. (2003) , Eppig et al. (2010) and McGuire and Coelho (2011).
Developing and maintaining human brains make other demands on dietary inputs beyond the caloric; also required are amino acids, fats, proteins, and a host of assorted micronutrients. In the ancestral environment animal source foods were virtually the only source of these nutrients that could be accessed in sufficient quantities. See Leonard and Robertson (1992) and Milton (2003), Leonard et al. (2007), Krebs (2009), and Milton (2015).
It is possible that the current human status at the top of the food chain has biased us against thinking about early hominids scavenging for protein at the expense of animals endowed with greater natural weapons and defenses (e.g. claws, fangs and/or body mass).
This was long before humans controlled fire and food was cooked; the control of fire and cooking increased the ability to process and absorb protein. Raw (uncooked) foods are not easily absorbed by the human gut. After fire was controlled and used, the human brain had the resources for continued growth and evolution. Wrangham (2009, pp. 96–103) dates some cooking to Homo erectus whose beginnings predate the present by approximately 1.9 million years. Wrangham also ascribes various changes in the anatomy and physiology of the progenitors of H. sapiens to cooking.
A vivid example of instinctual cooperation is found in the African honeyguide bird; it deliberately attracts human attention and guides humans to bee hives where the humans harvest the honey and the birds eat the grubs and beeswax. We know that this behavior is instinctual rather than learned because the honeyguides are brood parasites; like cuckoos, they do not raise their own chicks. Brood parasites deposit their eggs in the nests of other birds, and the foster parents, hatch, feed and raise the honeyguide chicks.
We frame this scenario in conjunction with the growth of hominid brains; however it is important to realize this model, a positive-sum game, underlies the evolution of cooperation for all species. Organisms, mindless or brainy, “cooperate” because it is beneficial to all cooperators; the benefits may, or may not, be equally shared, but all cooperators are net benefiters. This is why cooperation evolved; alternatively it is the evolutionary basis for cooperation.
In the cooperative case A and B fight together against competing carnivores.
The numeric values in the payoff matrix are largely heuristic. The value 1.2 could be replaced with any number greater than one; the values 0.8 and 0.4 could be replaced with any values that had both values less than one, but greater than zero, and had the former greater than the latter.
Darwin speculated that it was sexual selection that made large brains attractive to the opposite sex; if females found brainier mates more attractive, then brainier males would have more surviving descendants. Following Darwin, Cronin (1991) argued that the human brain was analogous to the peacock’s tail in that it was for to attracting mates, even though it does have some significant ecological costs among the Peafowl. The reason why sexual selection is relevant is that it offers an explanation for the evolution of brainier hominids in spite of the brain’s large costs (just as sexual selection provides an explanation for the peacock’s tail despite the costs it entails in terms of predation).
An example of the cost/benefit calculus is that of brains versus brawn. Because the brain is so costly to develop (see footnotes 14 and 15) and maintain, getting larger brains must entail reductions somewhere else in the organism’s body. Big-brained but physically smaller carnivores (e.g., lions or wolves) face severe disadvantages when competing against conspecifics with larger muscles and body mass. Lions and wolves acquire and ingest large amounts of protein, but have not evolved the large brains that characterize human beings. Again (as noted in the main text) the acquisition of large quantities of protein is a necessary, but not a sufficient condition for the evolution of large brains. Again (as noted in the text and in Footnote 22 above) the evolution of the human brain is anomalous, akin to the peacock’s tail, with sexual selection also being the likely explanation.
The stag game, like the PD, involves strategizing players. Unlike the PD, in the stag game there are two Nash equilibria: (a) in the Pareto efficient equilibrium the two hunters cooperate to bag a stag yielding each hunter say 3 units of meat, and (b) in the risk dominant equilibrium each hunter bags a rabbit yielding just one unit of meat. In the stag game, players will cooperate (hunt the stag rather than rabbit) only if they can be made to believe that the other player will cooperate because if one hunts stag while the other hunts rabbit, then the stag hunter gets no meat while the rabbit hunter bags two rabbits. In our Hominid Scavenging Game, there is, again, no presumption of strategizing players; rather it is the process of mindless evolutionary selection in the ancestral environment that would probabilistically have favored the survival of individuals who cooperated over those who did not.
Our model focuses upon inter-species competition. As an anonymous referee pointed out, discussions of this type of competition were once frequent in the literature but have been crowded out to a large extent by the over-emphasis of intra-species competition. Although we acknowledge that interactions between these types of competition may exist, we see them as beyond the scope of this paper.
This scenario also explains the acquisition of protein before cultural developments (the acquisition of fire, cooking, and increased cooperation) which further aided human evolution. This scenario underlies the evolution of human cooperation in the actual environment(s) and temporal sequence in which it occurred.
As an anonymous referee pointed out primate research reveals that there are tradeoffs associated with living in larger groups. In a study of the limits to primate group sizes, Dunbar (1992, p. 469) discovered that “species will only be able to invade habitats that require larger groups than their current limit if they evolve larger neocortices.”
Large herbivores (musk oxen, water buffalo) cooperate by creating defensive formations to repel predators; Alcock has numerous examples of defensive formations, mobbing behaviors, and other forms of intra-species co-operation.
Changes in the brain are nuanced. Calvin (2004, pp. 96–97) explains that most of the evolutionary data suggest that the emergence of the cognitive planning associated with hitting moving targets did not arise in a specialized “ ...bump on the head that could be labeled Hand-Arm Planning Center. ...Certainly there is much evidence suggesting that oral-facial movement planning can overlap that for hand-arm—and with that for language, both sensory and motor aspects.” That is, it is most likely that “major portions of the brain [increased] together.”
A good example of the coevolution of genes and culture is in Wilson (2015, p. 64). Paraphrasing Wilson, lactose intolerance is common among humans after weaning. Pastoralism and the herding of cattle, goats, horses, and sheep made milk a source of adult nutrition. Over generations a genetic aberration that made the human adult digestive system lactose tolerant became widespread among herders. The ability to utilize milk products made the animals more valuable, thus increasing incentives to herd these animals; their numbers and the population of lactose tolerant humans dependent upon milk-based nutrition both increased.
Box 4 includes a host of major and minor developments. Among these are: language, male-female pair-bonding, fire, gender based division of labor, tool-making, problem-solving, and abstract thinking.
Wrangham explains that cooking allowed the human gut to evolve into a smaller organ that required fewer calories to process and digest foods. This released calories and nutrients that had previously been claimed by the gut’s processing demands to be reallocated to the evolving brain. Humans have by far the smallest guts and the biggest brains in the primate family; these developments are synergistically intertwined.
“Although culture has for many decades been envisioned as an evolutionary process, there is little agreement about its precise nature, importance, or relationship to genetic evolution . ” Wilson (2002; p. 28; emphasis added)
An anonymous referee called attention to Chapais’ (2008) theory that pair bonding gave birth to human society. As Chapais (2011, p. 1277) explains: “...pair bonding ... brought about the multifamily composition of human groups, with enduring associations between mothers and fathers enabling children to recognize their fathers. This, in turn, made it possible for children to recognize their father’s relatives; that is, pair bonding would reveal the underlying genealogical structure and create bilineal kinship.” This was “a factor alleviating conflicts between male affines. Similarly, grandfathers, brothers, and uncles would recognize their transferred kin and their affines [their mates] instigating a state of mutual tolerance.” (Chapais 2011; p. 1277).
Chapais (2008, p. 183) argues that “the sexual division of labor was the outcome of a specific concatenation of unrelated events, namely, (1) bipedalism, which rendered gathering possible, (2) pair-bonding, which created food-sharing biases among primary kin, and (3) a chimpanzee-like male hunting bias, which operated as both a template and a spring-board for complete sexual specialization.” While the nuances of this argument are beyond the scope of our model, it is not in conflict with the sexual division of labor in Box 4 (Fig. 1) with its positive feedbacks to both Cooperation (Box 1) and Protein (Box 2).
Adam Smith famously wrote: “The division of labor is limited by the size of the market.” As the absolute size of economic output increases, the returns to specialized economic activities increase, leading to increasing (absolute and per capita) output. This generates a “virtuous cycle,” or, in the context of this paper, coevolution. See Stigler (1951) and McGuire and Coelho (2011).
As noted earlier, there is evidence of cooperation among species that have small brains. Certainly early humans had brains, but cooperation has evolved throughout the animal kingdom among both creatures with large brains and those with tiny ones; large brains are not necessary for the emergence of cooperation.
Strategic thinking should not be confused with deception or mimicry. Chameleons, puffer fish, butterflies and a host of other species have behaviors that thwart predators and rivals. As examples, the chameleon does not have to think about what color his skin is to be, neither do stick insects have to think about how to look like sticks; these are innate actions accomplished without conscious thought. Strategic behaviors have to be planned and thought over, so perhaps non-cooperation and strategic behavior is a result of the large human brain. If so, this is paradoxical; game-playing and strategic non-cooperation were results of the large brain which resulted from cooperation.
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Coelho, P.R.P., McClure, J.E. The evolution of human cooperation. J Bioecon 18, 65–78 (2016). https://doi.org/10.1007/s10818-016-9213-z
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DOI: https://doi.org/10.1007/s10818-016-9213-z