The Mysterious Cities of Gold/Headscratchers

So what ARE the Olmecs? They say their ancestors built or somehow were involved with the cities of gold. Are they decended from the people of Mu, like Tao's family? They why do they look like Goblins?
 * They're survivors from the nuclear war between Mu and Atlantis. They look weird because of mutations from the radioactive fallout.
 * They were supposed to be aliens, but they were changed to the above in the dubs.
 * In the original French, they never were aliens either. Just a civilization living in periphery to Mu and Atlantis who hid and took refuge during the Great War, hoping they could stay in hibernation and outlive the disaster.