Khaberni - The human brain, relative to its size, is the most energy-consuming organ in the body, utilizing about 20% of our energy and constituting a significant proportion of our bodies compared to most other organisms. But why is that?
According to one hypothesis, our brains evolved to accommodate our broad social networks, as humans appear to inherently be social creatures.
The human brain weighs about three pounds (1.4 kg), which is equivalent to 2% of body weight, and the cerebral cortex constitutes three-quarters of this large organ, which is responsible for complex cognitive functions such as memory, language, problem-solving, and self-awareness.
With these functional capacities, humans can handle complex relationships within families, groups of friends, sports teams, work environments, and develop a broad social network that has many health benefits, according to studies.
Julianne Holt-Lunstad, a Professor of Psychology and Neuroscience at Brigham Young University, says: “The more socially connected people are, the higher their survival rates, and they have lower risks of heart disease, strokes, type 2 diabetes, depression, and dementia."
But these beneficial social connections impose a significant cognitive burden on the brain, which limits the number of stable relationships we can maintain, according to British psychologist Robin Dunbar.
To understand these limits, Dunbar studied "primates" such as monkeys, lemurs, and chimpanzees, and discovered a correlation between the size of the cerebral cortex in each species and the size of their stable social groups.
The data showed a clear proportional relationship; the larger the cerebral cortex, the larger the social group size.
For example, Dunbar found that the average size of a chimpanzee's social group is about 50 individuals.
Based on the relationship between the size of the cerebral cortex in over 30 species of primates and the size of their social groups, he concluded that the maximum number of stable social relationships for humans is 150 people.
Dunbar believes that this number has remained consistent since the emergence of modern humans and has not changed even in the age of social networking.
Dunbar tested his hypothesis by studying historical texts, archaeological data, and both ancient and modern human groups—from hunter-gatherer networks to Anglo-Saxon villages, Mormon caravans, and modern German camps—and found that the number 150 is consistently repeated.
- Closest circle: 5 people (closest friends or family emotionally).
- Next circle: 10 additional friends you see at least once a month.
60% of your social attention goes to these fifteen people.
- A larger circle consisting of about 50 people (whom you see at weekly social events).
- The widest circle, which completes the number to 150 people, are those whom you might invite to your wedding or feel no embarrassment in warmly greeting at an airport at 3 AM.
Dunbar adds: "If communication with individuals in one of these circles decreases, they gradually slip to further layers, and after a few years, they become just acquaintances."
Dunbar estimates that the average person has about 350 additional acquaintances above their 150-person network, and most of us can visually recognize about 1,000 other people, such as celebrities or leaders, without them knowing us personally.
But these external relationships, as he says, are "one-way."
The relationships within the 150-person circle, however, are reciprocal.
Scientific debate on the number
In 2021, a team of Swedish researchers published a study claiming that the number 150 underestimates the size of humans' real social networks, and an upper limit cannot be precisely determined.
Johan Lind, a biologist at the Center for Cultural Evolution at Stockholm University and one of the study's authors, says: "Dunbar's assumption is based on the idea that humans and non-human primates are subject to the same evolutionary pressures, but humans have greatly surpassed those limits."
While the availability of resources and predation risks limit the size of groups in other primates, humans live in completely different conditions—they attend football matches or concerts amidst thousands of people, then return to homes filled with food.
Lind believes this should allow for larger social networks.
With the spread of Facebook, Instagram, Discord, and Slack, it seems logical that digital communication could allow for expanding our social networks.
However, Dunbar believes otherwise, saying: "If you look at the frequency of interaction on social media, phone calls, or in-person meetings, you'll find the same circles repeating."
He adds that social media has only helped keep people within certain circles for a longer period but did not change the number or the actual quality of relationships.
Dunbar concludes, saying: "It's hard to get emotional support from someone you can't actually hug... Real-world communication remains the most genuine and closest."
