Interesting idea Raven. Love your avatar by the way. I suspect the reason why might be that the Olmecs were not represented with the cranial style found in the dispersal of these people. Now you have my interest piqued as to Olmec dispersal as I had known of them in th new World context only as being likely West African and possibly also connected with Asian migrations. However, in the Yucutan, the story gets very strange as there are skulls of a species of hominid whose skulls are simply massive. I'll surf around for the link, and post it once I relocate it.
You'll be amazed at the skulls.

Not only does the Olmecs have a link to Egypt and Peru they have also been linked to the Xi'an and Shuang people of central China. It is believed that the first Japanese Shogun was Sakanouye No Tamaru Maru who was an African helping the Mongoloids fight the Aboriginies of Japan (also of African origins) called the Ainu people.