Just as there was a first instant when someone rubbed two sticks together to make a spark, there was a first time joy was felt, and a first time for sadness. For a while, new feelings ere being invented all the time. Desire was born early, as was retreat. When stubbornness was felt for the first time, it started a chain of reaction, creating the feeling of resentment on the one hand, and alienation and loneliness on the other. It might have been a certain counterclockwise movement of the hips that marked the birth of ecstasy, a bolt of lightning that caused the first feeling of awe. Or maybe it was the body of a girl named Alma. Contrary to logic, the feeling of surprise wasn't born immediately. It only came after people had enough time to get used to things as they were. And when enough time had passed, and someone felt the first feeling of surprise, someone, somewhere else, felt the first pang of nostalgia. 
It's also true that sometimes people felt things and, because there was no word for them, they went unmentioned. The oldest emotion in the world may be that of being moved; but to describe it --just to name it-- must have been like trying to catch something invisible.
(Then again, the oldest feeling  in the world might simply have been confusion.) 
Having begun to feel, people's desire to feel grew. They wanted to feel more, feel deeper, despite how much it sometimes hurt. People became addicted to feeling. They struggled to uncover new emotions. It's possible that this is how art was born. New kinds of joy were forged, along with new kinds of sadness: The eternal disappointment of life as it is; the relief of unexpected reprieve; the fear of dying.

Nicole Krauss