How big is your brain compared to your fist?

In this brief guide we are going to answer the question ‘’How big is your brain compared to your fist?’’, We will compare the size of the brain with different animal species, including primates, and we will discover what is the reason for the size of the human brain.

How big is your brain compared to your fist?

The brain is much bigger compared to your fist. In fact, we could say that the brain is approximately two clenched fists.

With just one look you understand the message How do you read a sentence, use a computer or remember the way home? You do it with your brain, the great organ inside your head. The brain coordinates all your senses, makes you move and allows you to store memories.

The brain can do many more things. It is the center of operations of your body: it controls your emotions and your ability to speak, reason and dream. Oddly enough, you can only think about the fact that you have a brain because you have a brain

During the first years, the growth of the body slows down to focus all its energy on feeding it. That is the reason why, unlike other mammals, human babies remain so defenseless for so long. 

While a calf stands up and takes its first steps practically after birth, this feat takes about a year for a child, and it will be a long time before it can survive without the help of its parents.

What is the human brain like?

The human brain weighs between 1,300 and 1,400 grams, is 14 centimeters wide, 13 centimeters high, and has a length of 17 centimeters. The volume of the brain is approximately 1,350 and 1,500 cm3. If we were to extend the cerebral cortex, that is, the surface of the brain, it would measure 0.2 m2.

Compared to other animals, humans have one of the largest brains. Sure, taking into account the size of the body. Of course, elephants have bigger brains, but it only represents 0.2% of their body mass. In humans, the brain represents 2% of our body mass.

The human brain ranges from 1.2 to 1.4 kilograms in weight and is estimated to contain some 86 billion neurons. A whale’s brain can double this number, but it is not smarter for that.

The development of cognitive ability does not depend on brain size, but on more complex variables. The intelligence of a species is largely due to the so-called encephalization quotient, the result of dividing the weight of the brain by the weight of the body.

Other species

Some animal species, despite having small brains, outnumber others with heavier brains; This is the case of crows or rats, more intelligent than cows. Another prominent example is bees; Despite their tiny nervous system, they are able to calculate the volume of honey in the hive, measure distances, orient themselves and communicate socially.

Careful comparison of the human brain with that of our living primate relatives, including chimpanzees, has shown that the parts of the cerebral cortex that deal with high-level cognitive functions, such as creativity and abstract thinking, have increased its size in a striking way.

These cortical regions, known as association areas, mature relatively late in postnatal development. Some of the long-range neural connections that link these areas to each other and to the cerebellum (which is involved in voluntary movement and learning new skills) are more numerous in humans than in other primates.

Language, tool making, and imitation are localized in these enhanced networks. Even the ancient reward systems of the subcortical area, called the striatum (a center of activity for the neurotransmitter dopamine), appear to have been remodeled during the evolution of the human brain.

It’s very likely that this change served to pay more attention to social cues and facilitate language learning.

In the human species, the neuronal structure and density plays a determining role. This is what happens in the cerebral cortex, a superposition of neuronal layers that covers the cerebral hemispheres. How we humans achieve such unique brain-size development is still under debate.

Brain-size theories

The human brain stops growing at the age of ten, long before your body reaches physical maturity. This vital strategy is not repeated in other apes (although it has been proven in Neanderthals, an extinct human species) and is puzzling because it makes us smaller, more vulnerable and less productive for longer.

But what was it that powered our unusually large brain? There are several theories in this regard, including the social hypothesis, which suggests that the brain evolved to a larger size to help manage our increasingly complex social lives, or the expensive tissue hypothesis, which postulates that eating meat allowed brains will evolve.

However, a fundamental problem with these theories is that they depend on correlative data and therefore cannot unravel which is the cause and which is the effect.

The new research, conducted by researchers at the University of Saint Andrews (Scotland) and published in the journal ‘Nature’, has used an innovative methodological perspective to conclude that it was primarily environmental challenges, such as searching for food, that made us into the intelligent beings that we are.

Four challenges

The authors explored four types of challenges: ecological (me versus nature), ecological cooperative (us versus nature), competitive between individuals (me versus you), and competitive between groups (us versus them).

In this way, they concluded that the size of the human brain evolved in response to several factors that were 60% ecological, 30% related to cooperation and 10% related to competition between groups.

Interestingly, competition between individuals was relatively unimportant. The findings are intriguing because they suggest that social complexity is more likely to be a consequence rather than a cause of our large brain size, and that human nature is more likely to stem from ecological problem solving and culture than social relationships.

In other words, learning to survive developed our brain more than learning to solve the problems that others cause us.

What differentiates the human brain from that of other species?

Scientists already knew that the human brain is larger than that of other primates, our closest living relatives – the chimpanzee, bonobo, and gorilla – but the difference in size does not explain the characteristics and functions that make it unique.

How did Homo sapiens achieve that extraordinary brain volume? A team of researchers has developed a model that shows that our gray matter constantly evolved over time (more than 3 million years), from which it follows that it is unlikely that our intelligence has been selected for a particular behavior.

“The first hominids had a similar brain size to chimpanzees, and they have increased dramatically since then. Therefore, it’s important to understand how we got here,” says Andrew Du, a paleobiologist at the University of Chicago and a co-author of the work.

Several hypotheses are based on changes in diet, better blood flow, or metabolic changes to drive additional neurons.

“Conventional wisdom is that our large brains had evolved through a series of staggered increments that each made our ancestors smarter,” says Bernard Wood of George Washington University, lead author of the study.

“Not surprisingly, the reality is more complex, without a clear link between brain size and behavior.” he concludes.

The new study, which has examined nearly 100 fossils (94 specifically) of 13 different human species dating back to when Australopithecus afarensis, whose most famous member “Lucy” was unearthed in Ethiopia, roamed the Earth, finding that the size of the brain it tripled over the past three million years, in a process that was probably slow and consistent, as opposed to a series of ‘staggered increases’.

Experts say the change from our ancestral family tree was driven by increasing complexity, as humans developed culture, language, and the ability to make tools. A long and hard training.

The researchers compare it to rubgy training: “The same goes for brains: we found that existing species developed larger brains, larger brain species appeared, and smaller-brain species became extinct,” says Du.

Far from being studied as a line of descent running from the 3.2 million year old Australopithecus to our close cousin Homo erectus, who lived half a million years ago, the specimens were divided into their family lineages. This allowed the researchers to compare the changes in each branch, as well as across different branches.

What they saw was that evolution within each group gradually boosted brain size.

As hominin species evolved (larger brains), the more limited brain populations were slowly being replaced by larger brains.

Meanwhile, the brain volumes within each species continually expanded with subsequent generations.

The study falls short of speculating on what forces drove the gradual change in brain volume, but it helps limit the hypotheses to those that support slow, steady rise rather than sudden, rapid steps.

Brain size is also not the beginning and end of cognitive functioning. While having more neurons could offer more opportunities to develop additional skills, the connections between them are vital in determining the functionality of the brain.

So, How big is your brain compared to your fist?

Well, it depends on your fist and your brain.

Certainly a fist is not half the size of the brain. In fact, some people take as a reference value that when you join your fists it is the size of your brain, but in reality it is a little bigger.

We cannot compare the first of a robust man to 50-kilogram woman’s fist

In fact, we could say that the organ that resembles the size of a fist is the heart. Let’s see, a fist is approximately 500 cm3, and a heart is 750 cm3.

As we previously reviewed, brain size can range from 1,300 cm3 to 1,500 cm3. That certainly means the brain is much bigger than two fists put together, but you could roughly have it as a 3d idea.

The brain was differentiated six million years ago when we separated from the lineage of our first cousins, the chimpanzees; adapting to being able to speak.

The relevance of brain size arouses some suspicion in certain areas, especially when it is linked to the most precious attributes of humanity (intelligence). But research continues to advance despite everything and produces results that can help us understand the brain-behavior relationship.

The size of our brain is one of the most obvious characteristics that we have as human beings. The complexity of this is related to the multiple activities of our species: there is cultural and language complexity, the brain is required to develop different tools and instruments that we need in our daily lives. That makes us unique

FAQS: How big is your brain compared to your fist?

Is your brain as big as your fists together?

It could be a good reference. The size of your brain is slightly larger than your two fists put together.

How big is the average person’s brain?

The average size of the human brain is between 1260 cm3 and 1130 cm3, with a weight of 3.3 lb.

Does a bigger head mean a bigger brain?

Yes, it is likely, although the size of the head also depends on factors such as muscularity and bone thickness.

Are all human brains the same size?

No, the size of the brain varies. In fact, the male brain is larger and heavier than the female brain.

What is inside the human head?

Inside the human head we can find the brain, eyes, ears and tongue.

In this brief guide we answered the question ‘’How big is your brain compared to your fist?’’We compared the size of the brain with different animal species, including primates, and discovered what is the reason for the size of the human brain.

If you have any questions or comments please let us know!


Brain Size – an overview | ScienceDirect Topics. (2012). Retrieved October 10, 2020, from website:

‌Koch, C. (2015). Does Brain Size Matter? Scientific American Mind, 27(1), 22–25.

Lewis, T. (2018, September 28). Human Brain: Facts, Functions & Anatomy. Retrieved October 10, 2020, from website:,volume%20of%201%2C274%20cubic%20centimeters.

Leave a Comment