Author’s note – This is the second post in a series titled ‘Demystifying the Brain‘. In this series, I will discuss some fundamental neuroscience concepts, and try to explain what scientists have been able to discover so far about how our brains work. You can find previous posts in the series here. If you have any questions, comments or suggestions, do leave a comment below.
Nothing in biology makes sense except in the light of evolution.
–Theodosius Dobzhansky (1900-1975)
Remember last week, when we discussed what the brain is, what it does, and how it goes about doing its job? We learned that the brain is a specialized part of the nervous system – the system which helps control and coordinate our actions. The brain controls the body by sending electrical signals through long bundles of connecting fibers called nerves. The nervous system is also responsible for receiving information from our senses (sight, hearing etc.) and building our worldview using that information. We talked about the energetic costs of maintaining the brain, and why some species may have chosen to maintain a small brain size in exchange for conserving more energy.
Today, however, we are going to take a slightly different approach, and go on a brief tour through the history of our species. And while doing this, we are going to try to answer a basic question – how could a structure as complex as the human brain ever have evolved?
As is the problem with any question of this nature, the answer must come through indirect means. Since we cannot invent a time machine (yet) and open a window into the past to observe evolution in action, our only recourse is to figure out what happened using two lines of evidence. The first set of evidence comes from the fossilized remains of animals, plants or other artifacts that have been preserved naturally; in these, we can look for missing links, or lost stages in evolution. The second method is to look at all the different groups of organisms living today and use their similarities and differences to estimate how far back in evolution they diverged from each other – i.e. when did their last common ancestor live and walk the earth?