Recently published in the journal Nature Neuroscience were the results of a study that showed a part of human brain structure (the amygdala) actually grows larger in those who have large numbers of friends and family members they see regularly. On the one hand, the related data was viewed as unsurprising for researchers, as it has long been recognized that the amydala rests at the center of the brain network that is important to socializing; while, on the other hand, the related data inspired researchers to ask if the size of the amygdala dictates behavior, or if behavior dictates the size of the amygdala, or if perhaps both occur as a matter of positive feedback. But really this finding is not even news, let alone insightful, at least for those with a deep understanding of the evolution of species on earth.
Predatory Socialization and Intelligence
It is now broadly accepted among evolutionary scientists that the single strongest driver for increasing intelligence within higher-level species has been cooperative social dynamics, particularly when survival for group members is enhanced by behaviors that require specific coordination. There is some evidence to suggest that pack hunting within certain advanced dinosaur species, such as Velociraptor, around 75 million years ago, involved such coordination. But by 55 million years ago the new-age mammals that took over after the extinction of the (non-avian) dinosaurs clearly included species that would display this type of behavior. One would become the common ancestor to dogs and cats, which split into dog-like and cat-like lines by around 50 million years ago. Both would give rise to numerous species that made a living through the highly refined coordination of efforts by group members, including those efforts related to the hunt, the defense of the group, and the protection of offspring. Reflecting the intellectual requirement of this social activity, dogs and cats would come to possess the largest brains for species at large when correcting for body size—at least for a time. All of this makes sense, because in order to coordinate sophisticated activities with others each group member must have some idea what others are going to do given the circumstance, which for highly intelligent beings that modify behavior on-sight and in real-time this will require a significant level of empathy and/or communication for group members.
Early Generalized Socialization and Intelligence
It was around this same time that other mammal lines found success using a different survival strategy. These were the first species known as primates that made a relatively small-scale living within the trees. As insectivores and/or herbivores, they would increasingly make use of social dynamics as a defensive strategy for dealing with a multitude of predatory threats—from above and below. In this case, the coordination of actions was not nearly as important as the communication that would warn of imminent threats, and better yet, to instruct what particular actions would best deal with specific threats. By 40 million years ago there would be very successful lemur and, especially, monkey species that would increasingly make use of highly social survival strategies requiring considerable brainpower. Pound for pound, primates would acquire brains 3 times larger than the average mammal, which had a brain around 4 times larger than the average reptile, which had a brain around 4 times larger than the average amphibian, and so on.
Intermediate Generalized Socialization and Intelligence
By 25 million years ago one or more monkey lines would give rise to the first ape lines, which would spend more time on the ground, while also facing more exposure to large-scale predators, especially dogs and cats. This would drive trends of increasing size and increasing cooperation for ape species, while this increased size and cooperation would allow apes to themselves become highly successful predators, especially with regard to hunting their monkey cousins. While being somewhat awkward hybrids at first, these species would increasingly become highly refined omnivorous generalists. By 15 million years ago the success of this survival strategy led to the rise of the great apes from lesser apes, with the former to include orangutans, gorillas, and chimpanzees. It was one or more species in the ancestral line of chimpanzees that would give rise to one or more hominin (bipedal ape) lines around 7 million years ago. Forced to travel in open areas, because of the decreased provisions and protection offered by shrinking forests in conjunction with cooler, dryer conditions, hominins would have to become increasingly cooperative, resourceful, and migratory; all while they lacked the raw athleticism and physical weaponry of their open-field predatory rivals (in Africa). To be successful in this realm rife with diverse and ever-changing threats would require an immense degree of coordinated group function, with strength in numbers being of utmost importance.
Advanced Generalized Socialization and Intelligence
This survival formula would allow a number of hominin lines to become highly successful by increasingly relying upon intelligence to overcome threats—including those physical, predatory, rival and, over time, microbial (e.g., by harnessing fire and cooking food). However, all along the way this success would increasingly be shared by many groups within a number of hominin species—all sustaining an existence by virtue of the same intellectual talents. With increasing access to the meat of all other large species using handcrafted tools and weapons, and especially through the use of increasingly sophisticated tactics and strategy for larger and larger hominin groups, this unprecedented hunting success would mean an unprecedented access to meat, not only allowing increased population size but increased brain size, as meat contains proteins critical to brain growth. Then, as rival hominin groups of increasing size were competing within the same niche, noting that some became more specialized to stay out of the fray, this competition between and within the most-intelligent generalist species ever to inhabit the earth would place all on an ever-steepening escalator for intellectual and technological advancement in both the social and material realms.