Are the Mayans & Aztecs ancestors of the modern mormons?

In a question i asked about the great civilizations that killed each other off in the book of mormon, I asked the whereabouts of these cultures and received answers that said these people were in south america and were related to the Aztecs and Mayans. If this is true then why are their beliefs so different without any similarities? Do the mormons think the world is ending in 2012? I don't know but, this seems highly unlikely.