Okay, my fault for skipping a lot of stuff in the middle, but a question began to burn in my mind. They have determined the full inscription, calculated the Olmec date, and correlated it to our Gregorian reckoning. The end of the article says:

  So, while 32 BC seemed awfully early for the Olmecs to carve this stone, there’s no way they could have done it later. (Or earlier, for that matter.)