How Does the Size of Our Brain Have Changed?

Written by Elif Gulce Batgi

Evolution is the process of development that may happen in different kinds of living organisms. The organisms have evolved to have the traits which best benefit them to survive and reproduce, mating and having off-springs. As much as the changes occur in behavioral and physical ways, there are remarkable amendments in the structure and function of the brain as well.

Humans have the largest brain ratio compared to the body sizes of other living creatures, also the most complex one [Evolution of, (n.d.)]. Different parts of the brain are specialized with particular functions and structures [Evolution of, (n.d.)]. Across approximately seven million years, the human brain had become three times bigger than it was [How has, 2013]. Moreover, most of this growth has occurred in the last 2 million years[How has, 2013]. The human brain is 15 times bigger than a mouse brain and 4 times bigger than a chimp brain [Evolution of, (n.d.)]. The organisms with larger brain size to body weight ratios are more capable in neuronal processing such as advanced cognition and intelligence. However, studies show us that the size of the brain is not directly correlated with intelligence in humans [Evolution of, (n.d.)]. The size and shape of the skulls in modern people’s brains are also different when compared to our earlier ancestors [Evolution of, (n.d.)]. Homo habilis, the first of our genus which appeared 1.9 million years ago, saw the crest level of brain size involve an evolvement in language learning in an area called Broca's area in the frontal lobe [How has, 2013]. The first fossil skulls of Homo erectus had brains averaging a bit larger than 600ml 1.8 million years ago [How has, 2013].

(Image credit: https://cdn.the-scientist.com/assets/articleNo/68649/iImg/41829/poncedeleon7hr.jpeg.)

The abovementioned things are about the development of the brain structure. However, there is a part that evolution affects the function of the human brain. Even though there are no accurate investigations and results it is still an undeniable fact. To understand the human brain and how it works it is necessary to learn the long past of human evolution and the selective pressures that shaped our ancestors [Human brain, (n.d.)]. One way to understand is to compare the differences and similarities among current creatures in cognitive processes and the neuroanatomical structures that underlie them [Human brain, (n.d.)]. Comparative analysis has contributed to understanding the behavioral and cognitive evolution of people by providing important insights [Human brain, (n.d.)]. It showed that most of the behavioral traits are also present in the other species while they were known as special for human beings such as eusociality in Hymenoptera [Human brain, (n.d.)].

Similar to the other traits of humans, behaviors, and structure of the brain are, were, and will always be open to development. After millions of years, our brains will be investigated and compared with that time situation like we do today. There is no shadow of a doubt that the brain will evolve.

References:

1. Evolution of the human brain. (n.d.). @yourgenome · Science website. https://www.yourgenome.org/stories/evolution-of-the-human-brain/.

2. How has the human brain evolved? (2013, July 1). Scientific American. https://www.scientificamerican.com/article/how-has-human-brain-evolved/ .

3. Human brain evolution. (n.d.). PubMed Central (PMC). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624727/.