If humans can build up their muscles, why can't they build up their brains? Or why can't humans increase their intelligence/IQ?
Neuroscientists generally agree that your actual IQ (Intelligence Quotient) is primarily determined by genetics. However, what you do with your intelligence is far more important, and a far better indicator of success, than the IQ number itself. Consequently there are skills that you can practice that will increase your mental effectiveness, making you more successful and a "smarter" person. Learning how to do logic problems, for instance, will improve a variety of thinking skills. Exercises that improve one's memory are always useful.
One way to think of it is to think of each mental skill - memory, logic, calculation, communication, and so on - as a separate muscle, requiring a different exercise for development. Traditional education concentrates on some of skills, but in order to develop others you have to work on your own. Also keep in mind that work ethic is a necessary skill for success. It doesn't matter how high your IQ is, if you can't organize yourself and complete tasks, you will accomplish little.
Of course we can increase our intelligence. It needs more practice and concentration. Intelligence is all about gaining knowledge. so yes, it is possible to increase your IQ.