The human brain is unlike any other! It has the ability to form eloquent language, to perform complex reasoning and be self-aware. But in order to truly understand these extraordinary abilities, it is vital to understand how these are formed.
One of the greatest tools that we use to understand the changes that our brain has gone through is comparison… yes, to monkeys. Comparing our own brains to primates’ brains allows us to understand the evolutionary changes that have possibly occurred – and what they mean for our complex abilities.
Our brains differ structurally from other primate brains: a fact that helps us understand the structural changes our brains have gone through over time. These include changes in size, organization, and density (of different types of cells). So, let’s explore and understand each of these changes!
Compared to other primates, human brains are large! In fact, data collected shows the difference between the brain sizes of nine different species of primates and homo sapiens (humans).
The numbers in the image to the left show the size of the brain in cubic centimeters. With a whopping difference of 961 cubic centimeters between the size of the human brain and the largest primate brain in the data set, it becomes quite clear to us that indeed, our brains are much larger than primate brains.
So could this, then be the reason for our advanced cognitive capabilities? Bigger brain equals bigger smarts? Well… not quite. Think about it! Extending our knowledge beyond primates, there are other animals who have brains that are larger than ours – elephants, for instance. But elephants do not have superior cognitive capabilities to us. So, our advanced cognitive abilities can’t only be based on larger brain size.
The change in brain size, however, does tell us about size increases in specific areas of the brain. For example, compared to one species of primate (rhesus macaques), humans have a larger parietal lobe, and more sections to process three-dimensional shapes. Similarly, we can see that the frontopolar cortex, Broca’s area, and the anterior insular cortex are about 6 times larger in humans than in chimpanzees. Increased size of specific parts of the brain means that our brain has a larger area (or, in some cases, more areas) dedicated to specific functions.
It is also important to note that while structural changes in the brain tell us a lot, similarities do too. The motor cortex and the primary visual cortex are much more similar in size between species of primates – and indeed, when comparing the motor and visual capabilities of humans with other primates’, they remain relatively similar.
Apart from changes in size, neuron density also tells us a lot. The bigger the brain gets, the less dense the neurons are packed – which leaves space for dendrites, axons, synapses, and glial cells (structures which receive and transmit information between brain cells and maintain neurons). Meaning, that the brain has more space for its neuron structures to establish more efficient connectivity patterns!
The image to the left shows the structure of a neuron, including dendrites, axons and synapses.
Interestingly, gene expression also contributes to humans’ advanced capabilities! Studies have shown that certain genes are expressed to a larger extent in the human brain (compared with the brains of primates); particularly, genes linked with synaptic transmission and plasticity (neurons’ ability to communicate with each other and form connections over time). Meaning, that humans have more of the genes which allow our neurons to work quickly and efficiently.
The changes that have been described above distinguish our brains from primates’ brains – and to a larger extent, signify the changes that our brain has gone through over time. And these same changes have contributed to the development of our complex cognitive abilities, which are at the very root of our human experience. So, as you read this article, make sure to think of your incredible brain – and its awesome evolutionary developments!
References
Verendeev, A., & Sherwood, C. C. (2017). HUMAN BRAIN EVOLUTION. Current opinion in behavioral sciences, 16, 41–45. https://doi.org/10.1016/j.cobeha.2017.02.003
What Are the Parts of the Nervous System? (2018, October 1). https://www.nichd.nih.gov/ https://www.nichd.nih.gov/health/topics/neuro/conditioninfo/parts
Isler, K., Kirk, E. C., Miller, J., Albrecht, G. A., Gelvin, B. R., & Martín, R. D. (2008). Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set. Journal of Human Evolution, 55(6), 967–978. https://doi.org/10.1016/j.jhevol.2008.08.004
Decoding brain evolution. (2017, July 6). Harvard Medical School. https://hms.harvard.edu/news/decoding-brain-evolution
Comments