The Olmecs (1200BC-300BC) in Mexico are an enigma. They appeared 'full blown' as a civilization, no record or history leading up to their culture. Their statues and frescoes show clear representations of the three racial groups, Negroid, Oriental and Caucasian. A lot of controversy surrounding this group. They are cited as the oldest 'civilization' in the new world.
Similar to Sumer, it appears. Wouldn't surprise me if they find evidence showing both had the same benefactor(s).