Why did the brain size of our ancestors increase?

There is no doubt that a larger brain has given us unlimited possibilities. The human brain is one of the most valuable parts of the body, occupying only 2% of its mass and using a fifth of the energy produced by the body. Moreover, about 2 million years ago, the brain size of our ancestors was no larger than that of a monkey.
One of the versions says that an increase in brain size was necessary for a person in order to make more convenient tools. Another claims that this helped our ancestors communicate better with each other. Perhaps the radical changes taking place in the world around them required corresponding changes from a person.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.