In this chapter, we learn that the brains of our ancestors were growing very rapidly for three million years to become human. The expansion of the surface area of the cerebral cortex launched the positive feedback loop between itself and the cultural evolution of the human species.
About three million years ago the brains of some hominid species began to gain volume much faster than the brains of all mammals including other primates. Since then those hominids had become human species and had tripled the size of their brains that became over six times larger than the brains of any other mammals of similar body size.
Even more importantly, the volume of their brains increased mostly due to the growth of their cortex, a many times folded thin and smooth layer of grey matter consisting of neurons, the brain cells with which we think.
Furthermore, the folding of the cortex had increased beyond the limits set forth by euclidean geometry. If we would take the brains of a mouse and increase them up to the volume of the human brains we would expect the surface area of the cortex to become 480 square centimeters following the rule of geometric similarity. However, the surface area of the human cortex is four times larger, 2000 square centimeters.
It isn’t by accident that the cerebral cortex resembles a crumpled paper ball. When the cortex is folding in a growing skull it follows the same seemingly random pattern as a crumpled sheet of paper when we are filling a glass with it. A fractal structure emerges that makes it possible to accommodate more cortical surface area into the skull. The bigger is the volume of the cerebral cortex the more folded its surface becomes.
A pathological decrease in cortical volume and folding leads to intellectual disability. Therefore there is a threshold in the size of the brain that defines human intelligence. We became human because of the unprecedented growth of cortical volume and cortical folding of the brains of our ancestors. The expansion of the surface area of the cerebral cortex enabled distinctively human broad cognitive maps to emerge.
Many theories have been proposed to explain the miracle of brain growth. Unfortunately, any theory about the events that took place millions of years ago can’t be conclusively proven.
The three most common hypotheses are climate change, ecological demands, and social competition. Anthropologists Drew Bailey and David Geary from the University of Missouri-Columbia in the USA analyzed data on 153 hominid skulls over the past two million years testing the feasibility of each hypothesis. They found out a clear correlation between population density and the size of skulls. The denser the population was the larger skulls it had. They also established a less clear correlation between the growth of the skull size and climate change.
A team of researchers from the School of Biology, the University of St Andrews in the UK proposed a model based on the metabolic cost of having larger brains. According to their model, the growth of the human brain was driven by “a combination of 60% ecological, 30% cooperative, and 10% between-group competitive challenges”.
The importance of between-group cooperation and the competition was also emphasized in the research of Robert Boyd and Peter J. Richerson from the University of California in the USA. They coined the term cumulative cultural evolution to underline the non-genetic nature of the adaptation that human ancestors went through using winnerless competition for better adaptive solutions between groups of strangers which were connecting and disconnecting frequently but randomly.
Also writing about cultural evolution, the father of modern anthropology Claude Levi-Strauss strongly underlined the special nature of such brain and cognitive map expansion driving winnerless competition. In the essay Race and Culture he wrote, “The great creative eras were those in which communication had become adequate for mutual stimulation by remote partners, yet was not so frequent or so rapid as to endanger the indispensable obstacles between individuals and groups or to reduce them to the point where overly facile exchanges might equalize and nullify their diversity.”
Indeed, the value of receiving the information that you already know is zero. The value of information that you can’t understand is also zero. Cultural evolution and winnerless competition lay in between. A bigger brain and wider cognitive map scale up the volume of information that you don’t know but can understand.
You will meet the term winnerless competition in the section dealing with the mathematical modeling of the natural learning process. The universality of some simple but deep ideas is stunning.
Humans need contact with dissenting people to gain access to information they don’t know and a wide cognitive map to understand them. In the face of frequent and severe environmental fluctuations, cumulative cultural evolution becomes a necessary condition for the survival of species and stimulates individual brains to grow.
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