A question worth of National Geographic which looks at a stody out of Canada (among other places):
Until the hot tub time machine becomes a reality, the answer to that question will remain as mysterious as the true identity of the '60s garage band ? and the Mysterians.
Nonetheless, academic minds are always trying to come up with a theory. Charles Darwin believed music was created as a sexual come-on. His idea is given credence by the universally acclaimed song of the summer, "Blurred Lines." (Note: The link goes to the Jimmy Fallon version played with toy instruments and is suitable for work.]
Other theorists believe music was an attempt at social glue, a way to bring early humans together into a close-knit community.
Chris Loersch, a senior research associate in psychology and neuroscience at the University of Colorado, likes that idea, and he's done research to try and prove it. He and Nathan Arbuckle, from the Department of Social Sciences and Humanities at the University of Ontario Institute of Technology, designed a series of studies to bolster it.