Stimulus > Response beings. That's it in a nutshell. Humans have mastered the art of developing more and more elaborate mating rituals.
To quote Dr. Robert Ford the character in the HBO series Westworld:

I read a theory once that the human intellect was like peacock feathers. Just an extravagant display intended to attract a mate. All of art, literature, a bit of Mozart, William Shakespeare, Michelangelo, and the Empire State Building... Just an elaborate mating ritual. Maybe it doesn't matter that we have accomplished so much for the basest of reasons. But, of course, the peacock can barely fly. It lives in the dirt, pecking insects out of the muck, consoling itself with its great beauty. I have come to think of so much of consciousness as a burden, a weight, and we have spared them that. Anxiety, self-loathing, guilt. The hosts are the ones who are free. Free here under my control.