system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are humans the only animals with brains as advanced as our own?

like, if having a bigger brain to use for problem solving, reason, etc. isn't necessarily a biological disadvantage, then why aren't there like a races of monkey people (us), tiger people, wolf people, etc.?
gpt
Being smart is certainly an evolutionary advantage, but it comes at a cost.  For example, for humans to walk on two legs and thus have hands free to use tools etc, and also to have huge brains, it makes human childbirth much more of an ordeal than any other animal, and it also means newborn humans are much more helpless than those of many other species.

So it's not that being smart isn't an advantage, it's just not the most economical advantage possible for most species.  With tigers, some may be smarter than others, but some also run faster or have bigger teeth, and those traits turned out to be more useful than the bigger brains.

The thing about evolution is, it finds *local maxima*.  Yes, humans are better adapted than tigers, as evidenced by the fact that we use them for rugs and not vice versa.  But that doesn't mean that if you make a tiger slightly more like a human it will be a better tiger.