In Brain Evolution, Size Speaks Volumes


The brain, though a small organ, is the most complex one; it serves as the center of the nervous system in all vertebrates and most invertebrates. Our brain size, however, has not always been the same; in fact, when humans started facing environmental changes and evolved bigger bodies, human brain size evolved as well.

What puzzled scientists was the question of which evolved first; the overall brain or larger brain regions. Studies have been conducted and their reporting stated that, in most vertebrates, brain size, abilities, and composition are due to a bigger overall brain size. The studies were conducted on 58 species of Songbirds, showing that, once the species evolved a bigger brain, brain regions controlling the mouth, beak, and the area for song developed extra capabilities.

This theory could also be applicable to understand human evolution, explaining that we may have first evolved larger brains, which then enhanced to allow evolved brain regions that control specific functions, such as language abilities. “Most neuroscientists believe there is nothing special about the way our brains have evolved, that what we need to do is understand the principles that underlie brain evolution in general, which is what this study involves,” said DeVoogd, a Cornell Professor of Psychology.

Scientists believe that bigger brains do not mean that everything is larger, but rather slowing and lengthening the development of certain regions. This process leads to more developed cortex; part of the brain that controls memory, perception, thought, language, and consciousness, and it is the last section to develop in animals and humans. The study discussed two theories; one suggesting that certain species were endowed with bigger brains because they need it to survive, while the other suggesting that some species evolved bigger brains, then larger brain regions developed to be used for specific complex functions. To reach a final conclusion, scientists measured the sizes of overall brains and 30 discrete areas that control behaviors in 58 Songbird species spanning 20 families.

Scientists used the brains of birds because it is relatively easy to obtain samples from lots of different species, and there is a lot of data on what different species do. Also, specific areas related to these functions can be easily seen in the brain. However, scientists noticed that in some species there are variations in certain brain regions that go beyond overall brain size; for example, areas that controlled singing were bigger in species that produce complex songs.

When it comes to humans, “it has always been controversial how we got to be who we are,” DeVoogd said. Since supporting a big brain requires great demands on energy and oxygen, some researchers speculate that changes in the diets of early humans, including the ability to find and cook high-quality food, helped facilitate overall human brain growth by supplying the needed calories and protein.

The human brain will always remain a complex maze where we can only try to sneak a peek.


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