Nature does not usually select for increase in intelligence greater than that needed for survival. Ants are collectively quite intelligent but they are probably not much smarter than they were 60 million years ago. The difference in our brains from other apes is not great. We have a greater density of neurons and a bigger, more convoluted brain. How difficult would that be for nature to select for in other species if intelligence gave a general advantage? Not difficult at all I think. Why doesn't evolution generally select for intelligence? And why have we been the exception?