Why Giant Brains Are So Rare

Giant Brains Are Rare

In Sapiens, Yuval Noah Harari explains that Homo sapiens means wise man. It is a term we have given ourselves as a species because we have large brains and use those large brains to set ourselves apart from the rest of the animals and creatures on the planet. There are some other species with big brains, but in general large brains are rare, and no other species has been shown to use their brain to the same competitive advantage as humans.
But if large brains have made us so competitive across the globe, why are they so rare? Harari writes, “The fact is that a jumbo brain is a jumbo drain on the body. … in Homo sapiens, the brain accounts for about 2-3 percent of total body weight, but it consumes 25 per cent of the body’s energy when the body is at rest. By comparison, the brains of other apes require only 8 per cent of rest-time energy.”
Our brains are incredibly active and use a lot of sugars for fuel, even when we are not doing anything. This is great news for those of us who are trying to go on a diet to lose some weight today, but it was not great news for our ancestor hunter-gatherer humans and proto-Homo sapiens species of the past. According to Harari, large brains essentially have a high up-front cost. There is a large energy up front energy cost that goes into maintaining the brain before a species can really use the brain to a competitive advantage, and that has been a barrier to other species developing large brains and using them in a way that could give them a competitive advantage.
Harari continues, “Archaic humans paid for their large brains in two ways. Firstly, they spent more time in search of food. Secondly, their muscles atrophied. … A chimpanzee can’t win an argument with a Homo  sapiens, but the ape can rip the man apart.” Strong thinking and reasoning skills are helpful today and are the reasons we live in houses, build rocket ships, and are able to develop vaccines to end global pandemics. However, our big brains are not always the best tool to bring to a fist fight. It is not obvious that better reasoning skills will help a species survive better than sharp claws and teeth, thick hides, or spiky spines. Evolution doesn’t have an end goal in mind, and for all species besides the human species that evolved into Homo sapiens, the big brain payoff simply wasn’t the evolutionary rout that provided the best chance of survival and spread. It wasn’t until the big brained human species began to live and interact in clusters and tribes, communicating and working together, that big brains and reasoning skills could begin to pay off and become competitive against larger animals with bigger muscles and more ferocious claws, teeth, and tusks.
Prioritizing Bad News

Prioritizing Bad News

I hear a lot of criticism of news and the tendency of news organizations to operate under a model of “if it bleeds, it leads.” The idea is that news is too negative, that it focuses too much on violent crime, corruption, and scandal rather than important but often somewhat boring news and developments. The negativity bias within the news is cited for our misunderstandings of violent crime, for tainting our views of politics, and for making us more cynical. But research that Daniel Kahneman presents in his book Thinking Fast and Slow suggests that maybe we shouldn’t blame news organizations for prioritizing bad news.


Kahneman writes, “the brains of humans and other animals contain a mechanism that is designed to give priority to bad news.” There appears to be physiological structures in the brain that allow our brains to react at super speeds to threats and injuries. If you hear a lion roar, your body is going to react to the threat immediately, before you consciously recognize exactly what you just heard. Similarly, if you touch a hot stove your body is going to react by jerking your hand back before you even feel the pain from the burn.


There is an evolutionary psychology explanation to the immediate reaction of our brain to threats and injuries. If you are deep at work and concentrating intensely on something, you don’t want your brain to be slow to shift gears and respond to the sound of an approaching predator. You want your brain and body to begin reacting to a dangerous sound immediately, to help you survive a potentially fatal attack. Animals, and early human ancestors, that could respond at a subconscious level to threats and injuries were more likely to survive and and reproduce, passing their super quick response system to the next generation.


Today we don’t have to run from lions as often as our ancestors, and despite what we might sense from action movies and the news, violent crime is actually rather low compared to historic levels. Our super quick threat detection system is still with us, but many of the evolutionary pressures that built it have been left in the past. Our threat and injury detectors are still operating, and Kahneman’s quote suggests that we see their influence in our lives reflected in the news we prioritize. Bad news may activate the same threat responses in our brain, and we may have an instinctual drive to know about understand threats and dangers. “If it bleeds, it leads” is not a grim decision made by news executives, it is a driving force of our evolutionary past, a part of our brain which once served us well, but now prioritizes bad news and biases our media.

Social Brain Hypothesis

The California Redwoods are amazing trees. They stand taller than any other tree, scraping at the sky as they compete among each other for sunlight. The trees can be packed together in a dense manner, all competing for the same light, all pulling massive amounts of water from the ground up enormous heights. What is interesting, however, is that the redwoods are geographically isolated, not stretching out across huge swaths of the continent, but contained within a fairly narrow region. They don’t compete against other species and spread, but mostly compete for sunlight, water, and resources among themselves.


In The Elephant in the Brain, Kevin Simler and Robin Hanson introduce the redwoods as a way to talk about the Social Brain Hypothesis in humans. The idea is that our brilliant brains developed so that we could compete against each other, not because our brains really helped us outsmart lions or obtain more resources than other animals. The authors write,


“The earliest Homo Sapiens lived in small, tight-knit bands of 20 to 50 individuals. These bands were our “groves” or “forests,” in which we competed not for sunlight, but for resources more befitting a primate: food, sex, territory, social status. And we had to earn these things, in part, by outwitting and outshining our rivals.

    This is what’s known in the literature as the social brain hypothesis, or sometimes the Machiavellian intelligence hypothesis. It’s the idea that our ancestors got smart primarily in order to compete against each other in a variety of social and political scenarios.”


I find this super interesting because in many ways we are still fighting among each other as if we were part of a small band of 20 to 50 individuals. We live in a world where food is relatively bountiful (for many but certainly not all) in the United States. We live in a world of online dating where finding a mate is more open to more people. Our “territory” today can be more private than ever and online niche communities can give us a new sense of social status that we could not have obtained in the past if we did not conform to the small groups of our high school, family, or work.


We seem to be in a place where we can let go of the pressures that the social brain hypothesis put on our early ancestors, but I don’t see people shedding those pressures very often. We can look at what has driven our species to behave the way we do and see that we don’t need to compete in the same way. We can recognize the great possibilities available to us and move in our own direction, but so often we chose to just show off and do more to impress others as if we still lived in small tribal bands. Rather than branching out, we seem to often retreat back to a group of 20 to 50 and compete internally in a way that wastes resources on our own selfish motives. I think that we should talk more openly about the social brain hypothesis and the ideas that Hanson and Simler present so that we can have a real discussion about how we move forward without pushing everyone to compete for things that we should be able to provide openly with new systems and organizations.


Humans will always be competing against each other in one way or another, but I think we are at a point where we can begin to decrease our competition. Our societies are at a point where we can be more constructive and inclusive if we can decide that we don’t need to participate in so many of the competitions that drive the world today and ruin so many of our lives. Changes along these lines would probably encourage us to live in smaller homes, live in a more community focused way, show off less, and help each other more. How we get there and give up some of this competitive nature I am not sure, but I think that we need to move in this direction to act as a global species and solve major problems such as climate change.

The Fast Brain’s Habits

Return on Character by Fred Kiel is a business book that argues that individuals with high moral character become better leaders in the business world and create more value for the companies they lead.  Kiel spends time in his book explaining how leaders with strong moral characters improve the workplace, and he also discusses ideas about where those moral character habits come from. He addresses the idea of the fast brain where our subconscious makes decisions and drives our emotions and behavior, and our slow brain where we rationally think through our ideas and actions. Focusing on the fast brain and its role in our behaviors, habits, and character Kiel writes,

“The fast brain is where all of our subconscious intuitions, cravings, habits, and emotions reside.  The fast brain’s primary purpose is to prove the subconscious “spurs” to drive behavior patterns aimed at bringing us safety, security, food, and social connection. … Our Fast brain also spurs behavior through habits — automatic responses such as putting our foot on the brake when we see a stop sign.  Those habits that determine how we relate to others, such as a reflexive response to tell the truth or own up to our mistakes, become our character habits.”

What Kiel’s quote shows me is that we will not be able to control, guide, or shape our character if we are not able to recognize the habits that are formed within our fast brain.  Increasing our level of self-awareness, focusing on our reactions to others, and being cognizant of our interactions with those around us will allow us to begin to form our fast brain into a tool that guides us along a moral path. We can use practices of self-awareness and perspective  to turn our fast brain into a machine that builds our character over time.  By focusing on our relationships with others and becoming comfortable with adopting strong character habits we can reach a level where we treat everyone around us better.

I think that an important component within the idea of shaping our fast brain is accepting the reactions and habits we have formed without realizing it. Often these habits can be quite negative, such as looking the other way when a person from a different ethnic background walks by, and it is important that we accept those habits rather than sweep them under a rug and hide them from ourselves. If we cannot accept that we have negative habits formed by our fast brain, then we never give our slow brain a chance to think through them and tumble through a solution to become a better person.  During the process of shaping our fast brain we must recognize the behaviors we want to change, but we must do so by accepting that we have those habits and behaviors before we tell ourselves how wrong they are, and before we castigate ourselves for having such thoughts and behaviors. An honest inner dialogue of reflection will help us grow, and give us a chance to help others grow by accepting our flaws, as well as the flaws of others, and finding a way to grow in a positive direction as a group.