In the beginning

Man didn’t start the music, it was always all around us: birds chirping in the woods, wind blowing in the trees, gorillas beating their chests, wolves howling kids laughing, women crying. We just add our verses and overtime it became a beautiful thing. 

http://tedgioia.com/music.html

https://www.google.com/amp/s/amp.theatlantic.com/amp/article/255945/

So they can measure it instead of listening to it? 

Started with rhythm....