They've found designs and artifacts at the bottom of the ocean, that shows signs of civilizations that predate sumeria and egypt.
Plus Norte Chico was settled around 9000 BC. Sumer was settled 'permanently' around 4500 BC. Norte Chico and about 11 other places around south america had all the making of civilization minus a few things.... but replaced with other things. For example, they had no Art- but they practiced rituals and traditions using mind altering drugs. They weren't heavy into domesticating animals - but they had complicated architecture and used symbols to communicate.
It was a different type of civilization but still probably more ancient.