system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why haven't other species evolved to be as intelligent as humans?

How come humans are the only species on Earth that use sophisticated language, build cities, develop medicine, etc? It seems that humans are WAY ahead of every other species. Why?
gpt
A slightly different answer: 

Species evolve qualities that are beneficial for survival, and passing on their genes. That's the only reason a particular trait gets selected and passed on in a species. Humans developed large front brains (which make us intelligent), because intelligence confers advantages for surviving and passing on our genes. So, humans developed big, smart brains for the same reason that we developed arms, that rhinos developed thick skin, that alligators developed an incredibly slow metabolism, and that owls developed acute vision. All of these traits are very helpful for helping the creature survive and mate. So, our asking "Why aren't other species as intelligent as us?" is very much like an alligator asking "Why don't other creatures have as slow metabolisms as we do?" or an owl asking "Why can't other creatures see or fly as well as we do?". The answer is that those traits aren't the ones that were helpful for those creatures to survive. Each creature developed the traits it did in order to overcome environmental challenges to survival, and it happens that intelligence was a huge help for primates in trying to survive, but not so much for alligators. Alligators don't need to be able to make tools or to fly to weather their environmental challenges. What would be more helpful is if they could slow their metabolism to the point that they only need to eat about once a year - and this is the trait they developed. The same goes for us. Intelligence is one of many evolutionary tools developed for survival, but by no means the most efficient one. Bacteria - stupid as they are - are better at surviving than we are.