Where do zombies come from?

I have started to read a bit about zombies and their past. My not-so-extensive research pointed to the depths of Haitian history and being rooted way back in the slave trade when Haiti was a brutal slave colony surviving only on imported slavery from Africa (as the local population had mostly been killed off).  One third of the slaves who arrived on the island were worked to death within 3 years. 

So when Haiti gained its independence it is no surprise that one of the biggest fears that plagued popular culture was the idea of becoming a mindless, identity less, helpless manual worker. During the 1800’s, evil voodoo sourcers on the island, were said to prey on dead bodies, bringing them back to life for grueling work in the fields.  The locals were not afraid of the ‘zombies’ (who were often thought to be their dead relatives and friends) but of becoming one.  They would go to great lengths to protect their deceased from this fate, sometimes even shooting a body twice to lessen the chances being preyed upon.