In its initial conception, the music of hip-hop was not intended to drive any encompassing social message or lyrical commentary. Of course, as a diasporic musical form, it is inherently political, but in 1970 not many individuals were rapping in the modern sense of that word, let alone dropping verses that deal with police brutality or socioeconomic marginalization. The “invention” of hip-hop is not unlike the trope of accidental ingenuity that we love to attribute to the creation of all our most beloved things, like Edison and the lightbulb, or Wozniak and the Apple computer. The tinkering in this case took place not in a Palo Alto garage, but in the recreational room of a high-rise apartment building in the South Bronx, just off the Expressway. https://www.youtube.com/watch?v=aHL6iKpZ8hc
A young Jamaican-American DJ, with knowledge of the dance hall culture of the country from which he migrated, made the simple discovery that there are some songs, and more pertinently, certain instrumental breaks of some songs, to which people enjoy dancing the most.