Barnes

Hi all. I signed up just to ask this question. I only know basic knowledge about this topic, and a thought just occurred to me. The human being takes roughly eighteen to twenty years until it becomes fully grown. Or something like that. For most animals, it seems to take no more than two years. Why does the human take longer to become fully grown than say a chimpanzee? Is it because humans, as the most evolved species (I guess), need more years as infants to fully develop into grown adults? I may have just answered my own question, but can anyone confirm this for me? Hopefully you understand what I'm saying, but it's hard to put into words. Thanks