Modern humans’ brains evolved approximately 200,000 years ago. For most of our species existence we lived as hunter-gatherers with maximum group sizes around 150 individuals. This persisted until 10 – 15 thousand years ago. From that time forward, our society has evolved a rapid pace—much more quickly than the biological evolution of our brains. Therefore, we are educating hunter-gatherer brains, but now in a modern society based on agricultural histories, which changed us from nomadic social groups to sessile, agricultural groupings.

Social group (class and school in this discussion) size really does matter. All teachers know this. Give a teacher too many students, and the best he or she can do is lecture to the masses, but not interact with the individual in a meaningful way. Too few students, and he or she does not have enough learners to create a community of learners that interact, encourage, and teach one another. I have long felt that classes of 15 – 20 students were the size with which I felt most effective as a teacher, or a total of 45 – 60 students to have contact with throughout a day and I would have to get to know throughout a term. I have had the luxury of this experience. However, this is not the norm for the typical public school secondary teacher. The norm is 5 classes of 30 – 40 students, or 150 – 200 students a day that a teacher interacts with each day and must get to know throughout the term. I’ve been in the experience of teaching 150 students and felt that was my limit to how many I could work with and effectively “know.” Though I could know this many, effectively teaching, assessing with writing assignments and projects, required smaller numbers just for logistical reasons.

My personal experience as a student and my professional experience as a teacher tells me that classes should be smaller, for logistical and social reasons, and schools themselves should be smaller as well—hundreds of students housed together, not thousands. Turns out there might be some research to support my “gut.”

Evolutionary psychologist, Robin Dunbar, has discovered a link in primates between brains size and average preferred social group size—the larger the brain, the larger the acceptable social group size. The more neural connections, the greater ability to manage the intricacies of neural information required for social interaction. In Apes and Old World monkeys, most species effectively lived in groups of 5 to 50. Comparing brain size of the different species of primates and effective social group size, then extrapolating and adding humans to this chart, the predicted, highly functioning social group size for humans is around 150. Interestingly, this size matches natural human group sizes, from military companies, Hutterite farming communities and even average size of hunter-gatherer bands. It also matches my (an probably many teachers) experience as well.

While we may be able to remember up to 2000 people, according to Dunbar’s research, the maximum number of social interactions tops out at around 150 individuals. In hunter-gatherer bands, this translates into groups splitting when they approach this maximum size of 150 individuals. In schools, this translates into smaller social groups, clubs, sports teams, classes, and unfortunately then cliques. If the maximum number of individuals one can know is around 150, then when put into groups larger than that, the individual must dehumanize on another. To not do so would be too overwhelming for our senses. Imagine trying to maneuver through an urban setting, or a school setting with many hundreds of individuals passing on the street or in the hallway, and then trying to manage all those social interactions. You would never get anywhere. The only option is, to at best acknowledge presence of most of the other individuals, but for the most part you must ignore most other individuals. To do otherwise would simply be overwhelming with too many social interactions to mentally process.

There appears to then be a mismatch between our human brains which evolved over thousands of millennia as sparsely populated hunter-gatherers and the now densely populated, noisy, modern world in which we live. This background overstimulation might very likely be the cause for such high rates of mental illness—the highest rate of which occurs in the most developed and urbanized environments as well. The most prescribed drugs in the United States are antidepressants. Additionally, 10% of American boys are prescribed ADHD stimulants such as Ritalin. Why predominantly the boys? In a TED Talk, Ken Robinson said that many children weren’t suffering from a disorder that needed pharmaceutical treatment. They were suffering from childhood. He went on to say that, if you take a child and make them sit and do clerical work for 8 hours a day, then yes the might get bored, fidget, and even act out. Maybe being forced to sit still in too-large of social groups is just too much to ask of many of our children—especially the boys—who need to be out “hunting and gathering.” If so, what ramifications does this have for how we design schools, classrooms, and curriculum? Maybe us educators need a better education in our evolutionary history as we continue to reform (or evolve) our schools for the future. To do otherwise, might simply exacerbate the problem and marginalize more and more students, requiring more and more medical intervention.

To dig deeper into this, I highly recommend the book Pandora’s Seed by Spencer Wells.