Ska is simple, fun music that cares little for anything other than being fun, and is often gleefully immature.

Ska, as youngsters know it today, was reinvented by the 2-Tone movement in the UK (specifically Coventry) in the late 70s. The scene was overtly political and as @NuPNuA has stated was a deliberately multicultural movement, hence the name.

If you want to hear some original ska from Jamaica then have a look for songs by Prince Buster but beware you will find some historical attitudes.