The Human Brain is where our memories are stored and where the management of all of the 'automatic' body systems are controlled from.
The central nervous system, comprising of the brain and the spinal cord, are continually working to manage our body systems and to complete tasks that we wish to do. Examples of these tasks are walking, catching an object, breathing, detecting and fighting infections, controlling our heart beating, etc. All of these are managed by our brains on a subconciouse level, we do not need to think about them, they just happen.
The brain is also a memory store and can return an answer to a question instantly. When we think of a question the brain instantly returns the answer that we have been taught is correct.
When a computer wants some information, it has to go through a process of searching through all the information it holds to find a match. Using indexes and writing the program code to be more efficient allows a computer to return the information more efficiently but the brain seems to 'know' the answer immediately (if the person has tried to remember it).
The brain also gives people the ability to think and come to new conclusions, new in that this information was not in our memory store before. But now that this new information has been thought about, it will be stored in the brain for future use. This thinking process is amazing. It can be used for storing and understanding information from televisions and films. In this case the brain receives information in the form of sound, words and images; yet it is able to understand and store this information, sometimes for life!
The brain can also take in detailed information such as mathematics, science, languages and can 'learn' it and allow people to remember it when required.
I emphasise the above functions of the human brain. Although the brain is immensely complex and immensely capable, it would be of no consequence whatsoever if there was not this conscious human being which inhabits the body in some way.
The human being is 'dead' if this consciousness is not present. The body may be breathing, it may seem to be alive but if the consciousness has gone then the person is gone.
How could such a consciousness evolve? The complex brain with it's memory store and hugely complex control systems for operating the immensely complex body functions, would have to exist in an advanced form before the human being could exist.
Was there an evolutionary stage where humans without consciousness and the ability to think existed? Purely robots, wandering around planet Earth responding only to external stimulii and somehow knowing how to stay alive?
And then, when enough memory cells had come into being, the conscious person magically appeared and started thinking and reasoning!
I don't think so! The animal kingdom, from which humans supposedly evolved, has the ability to make conscious choices and decisions. These animals are not as complex as humans but they are still hugely complex conscious beings and can make decisions about what they do.