On this site I have advanced the claim that brains do not make minds. One question that is raised by such a claim is: if brains do not create minds, what is it that brains do? I believe the best answer we can give to this question is: the brain is an organ that helps other parts of the body outside of the skull do their jobs.
Let's consider how the brain helps other parts of the body do their jobs. By controlling autonomic functions, the brain helps keep the heart and the lungs doing their jobs. By being a terminus point and coordinator for nerves throughout the body, the brain helps those nerves do their job. So, for example, the brain helps the touch-sensitive nerves at the tip of your fingers do their jobs.
The brain also helps the senses do their jobs. Much of the brain is involved in helping eyes do their job, by helping sensory inputs form into an image you see in your mind's eye. Some of the brain is involved in helping ears do their job, by helping you decipher auditory inputs that would be unintelligible without a brain. Some of the brain is involved in helping your lips and tongue do the job that they do in speaking. Because of all of the subtle requirements of speech, speaking requires quite a bit of brain involvement. If humans had full-blast telepathic powers as good as speech, we might require a much smaller brain.
The brain also helps muscles and bones do their job, by helping to provide the coordination needed for complex muscular movements such as walking. It could be that the brain is a kind of storehouse for learned complex muscle movements. Accounting for such a kind of “muscle memory” is much easier than accounting for episodic memory.
The brain also has some involvement in sexual function, things such as erections and orgasms. The brain also has some involvement in the endocrine system, maintaining balance and maintaining body temperature and homeostasis. So in all these things we have a large variety of jobs that the brain does. We can combine these examples to form a “lean and mean” concept of what the brain does, by saying: the brain is an organ that helps other parts of the body outside the brain do their jobs.
This is the core of what we know about what brains do. Our scientists should have stuck with such a empirically well-founded core, and been extremely wary about adding a great mass of other unwarranted ideas, such as the idea that the brain stores episodic memories or conceptual learning, or that brain creates abstract ideas, or that the brain creates your self or consciousness.
Given all the different roles the brain has for helping other parts of the body, we have no problem along the lines of “the brain is bigger than it should be if it doesn't make your mind.”