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The “Machiavellian intelligence” hypothesis (or the “social brain” hypothesis) posits that large brains and distinctive cognitive abilities of humans have evolved via intense social competition in which social competitors developed increasingly sophisticated “Machiavellian” strategies as a means to achieve higher social and reproductive success.

In humans, the brain is very expensive metabolically: it represents ≈2% of the body's weight but utilizes ≈20% of total body metabolism at rest. The two burning questions are what factors drove the evolution of brain size and why our ancestors 50,000 years ago needed the brains they had. A number of potential answers have been hotly debated focusing on the effects of climatic, ecological, and social factors. One controversial set of ideas coming under the rubric of the “Machiavellian intelligence” or “social brain” hypothesis identifies selective forces resulting from social competitive interactions as the most important factor in the evolution of hominids, who at some point in the past became an ecologically dominant species. These forces selected for more and more effective strategies of achieving social success (including deception, manipulation, alliance formation, exploitation of the expertise of others, etc.) and for ability to learn and use them. The social success translated into reproductive success selecting for larger and more complex brains. Once a tool for inventing, learning, and using these strategies (i.e., a complex brain) is in place, it can be used for a variety of other purposes including coping with environmental, ecological, technological, linguistic, and other challenges.

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The model studied here is based on a notion of “cerebral capacity” as a measure of the number of different memes/ideas/strategies that the brain can learn socially and use. This measure is analogous to “carrying capacity” used in ecology to characterize the number of individuals that can survive in a given ecological niche. During the cognitive explosion phase, the cerebral capacity evolves faster and to a larger degree than learning ability. Both the average Machiavellian fitness and the average number of memes per individual achieved during the cognitive explosion phase are largely controlled by the average cerebral capacity. The importance of cerebral capacity in our model suggests that incorporation of this notion into theoretical and empirical studies of cognitive processes can potentially be very beneficial.

The model studied here aims to describe only some aspects of the early stages of the evolution of intelligence. The model should not be applied directly to actual human history and society. Our model does not aim to explain why a cognitive explosion has occurred only in the lineage leading to modern Homo sapiens. Rather, it tests whether a particular set of explanations advanced and discussed in detail by many, which places special emphasis on the achievement of “ecological dominance” and on competition in regard to social competencies, is plausible from the population genetics perspective. Alternative explanations do exist, and much more work remains necessary to better understand the origins of human uniqueness. As with most other mathematical models used in evolutionary biology, the goal of our model is not to prove that a particular phemomena arises as a result of particular factors. Rather, we wished to explore the logic and plausibility of the arguments used to explain the phenomenon, to identify important factors, parameters, and time scales, and to check the robustness of conclusions to variation in assumptions.

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Overall, our results suggest that the mechanisms underlying the “Machiavellian intelligence” hypothesis can indeed result in the evolution of significant cognitive abilities on the time scale of 10 to 20 thousand generations.

https://www.pnas.org/content/103/45/16823

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It should come as no surprise that evolutionary mechanisms were suggested to play a role in cognitive evolution. Evolutionary mechanisms that lead to the cognitive explosion of the human lineage were not specified in the above paper and this is where I'd like to make my own suggestions, my 2c.

I'm coming to think that co-evolutionary happenings had a role to play. To give an example first, one could ask; Did evolved tools make us smarter, or did we evolve to become smart enough to make tools? 

And the answer is that it is a co-evolutionary thing, a sort of bootstrapping thing where we get a little bit smarter, smart enough to make tools and then those tools make us smarter so, building and building and building.

My thoughts are that perhaps like with human intelligence and tool use, Machiavellian strategies and self-domestication made it easier for us to communicate with one another and cohabit within complex societies.

In a similar way to how a wolf became a dog, perhaps it too is how an ape became a human.
 

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Another theory that tries to explain the growth of human intelligence is the reduced aggression theory (aka self-domestication theory). According to this strand of thought what led to the evolution of advanced intelligence in Homo sapiens was a drastic reduction of the aggressive drive. This change separated us from other species of monkeys and primates, where this aggressivity is still in plain sight, and eventually lead to the development of quintessential human traits such as empathy, social cognition and culture. This theory has received strong support from studies of animal domestication where selective breeding for tameness has, in only a few generations, led to the emergence of impressive “humanlike” abilities. Tamed foxes, for example, exhibit advanced forms of social communication (following pointing gestures), pedomorphic physical features (childlike faces, floppy ears) and even rudimentary forms of theory of mind (eye contact seeking, gaze following). Evidence also comes from the field of ethology (which is the study of animal behavior, focused on observing species in their natural habitat rather than in controlled laboratory settings) where it has been found that animals with a gentle and relaxed manner of interacting with each other – like for example stumptailed macaques, orangutans and bonobos – have more advanced socio-cognitive abilities than those found among the more aggressive chimpanzees and baboons. It is hypothesized that these abilities derive from a selection against aggression.

On a mechanistic level these changes are believed to be the result of a systemic downregulation of the sympathetic nervous system (the fight-or-flight reflex). Hence, tamed foxes show a reduced adrenal gland size and have an up to fivefold reduction in both basal and stress-induced blood cortisol levels. Similarly, domesticated rats and guinea pigs have both reduced adrenal gland size and reduced blood corticosterone levels.[33][34] It seems as though the neoteny of domesticated animals significantly prolongs the immaturity of their hypothalamic-pituitary-adrenal system (which is otherwise only immature for a short period when they are pups/kittens) and this opens up a larger ”socialization window” during which they can learn to interact with their caretakers in a more relaxed way.

This downregulation of sympathetic nervous system reactivity is also believed to be accompanied by a compensatory increase in a number of opposing organs and systems. Although these are not as well specified various candidates for such “organs” have been proposed: the parasympathetic system as a whole, the septal area over the amygdala, the oxytocin system, the endogenous opioids and various forms of quiescent immobilization which antagonize the fight-or-flight reflex.

https://link.springer.com/article/10.1023%2FB%3ARUGE.0000033312.92773.c1

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Redgreenvines said: I think it is better to back away from evolutionary concepts when examining cognition especially as common use of the word evolve is directed towards more everyday learning and behavior improvement, completely missing the whole selection + mutation + speciation phenomenon that is core to evolution in the world of science.

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In the model, genes control brains which invent and learn strategies (memes) which are used by males to gain advantage in competition for mates.

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Jewstress said:

I purposefully isolate from people in every aspect possible.

I find 90% of my interactions with anyone outside of my immediate family to be very frustrating.

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anyway, if you want to redefine the meaning of scientific terms, do so at the top of your page,

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