Most of us believe in the fact that we use only 10% of our brain. In an average, an adult spends 20% of the total glucose burnt to sustain the brain’s energy requirement, while in children the value goes up to 50% and in infants, it is 60%. As a matter of fact the brain requires a lot of energy to function properly, why has the 90% of the supposedly used fragment of the brain didn’t vanish in due course of evolution? Why is it present till now? Watch the video below to get an answer to the question.