How did the dolphin and chimpanzee become so intelligent through natural selection?

What challenges does a dolphin or chimpanzee face in it's environment that would cause only the most intelligent to survive and reproduce making the offspring increasingly more intelligent? How is a dolphins challenges its faced with different than say a sharks, which is not as intelligent as a dolphin.|||The chimpanzee became "so intelligent" the same way humans did; isolated populations of chimps devised ways of dominating their environment, and by selective "partitioning" of the smarter population eventually separated themselves from their ancestors (a group of earlier apes that you and I have in common with the chimps).





Sharks have not evolved to be any smarter because they began with less raw material. A shark is a fish. What do they teach in school these days? It is not impossible that in a few million years, sharks will evolve into something smarter, but it is unlikely because something is already dominating that opportunity.|||It has been scientificaly proven that mammals that live in the water have a much more developed brain than mammals that live on land. It has also been theorized that apes once lived and dived around water, reason for humans having such a developed brain.|||They didn't. God made them that way.|||Intelligence improves an animal's chances of survival, but brain tissue is costly to feed (we've all heard that our brains consume 25% of the calories we eat, even though they are only 2% of our body weight). Therefore an evolutionary optimum is reached when more smarts requires more calories than the animal can provide.|||Dolphin,Seals,Parrots,Orcas,Chimpanzees, and another animal that have well-developed brain often must think fast for their live,otherwise they will be dead.Since they have to think fast,Their brain will become bigger for thinking fast.But the intelligent of an animal is depend of its live.