The earliest humans were scavengers. We hid behind trees as the big cat took down the antelope. And then waited as the hyenas stripped the bones. Only then did we approach the remains of the dead creature, breaking the bones with rocks, getting at the marrow. We were the lowest of the low, but even then our intelligence, and maybe something other than that, a desire for something more, enabled us to devise better ways of doing what we wanted to do, so a particular technology evolved. Smashing the bones lost some of the marrow. Better to somehow snap off the ends of the bones, suck out some of the liquid core, then use a long twig to push out the remainder.
This leaves you with a cylinder of hollow bone.
Greater dexterity, ingenuity, meant more food for our offspring. In any triangle the sum of any two angles is less than two right angles. We blew the marrow from the bones into stone bowls, and the bones, at some point, became flutes. Those of us with the quickest minds and the quickest fingers passed on our genes. The marrow suckers became flautists and fiddlers, guitarists and concert pianists.