In his 1976 book The Twelfth Planet, Russian-American author Zecharia Sitchin claimed that the Anunnaki were actually a race of extraterrestrial beings from the undiscovered planet Nibiru, who came to Earth around 500,000 years ago in order to mine gold.

According to Sitchin, the Anunnaki genetically engineered homo erectus to create modern humans to work as their slaves. Sitchin claimed that the Anunnaki were forced to leave Earth when Antarctic glaciers melted, causing the Flood of Noah, which also destroyed the Anunnaki’s bases on Earth. These had to be rebuilt and the Nephilim, needing more humans to help in this massive effort, taught them agriculture.

Ronald H. Fritze writes that, according to Sitchin, “the Annunaki built the pyramids and all the other monumental structures from around the world that ancient astronaut theorists consider so impossible to build without highly advanced technologies.“Sitchin also claimed that the Anunnaki had left behind human-alien hybrids, some of whom may still be alive today, unaware of their alien ancestry. Sitchin expanded on this mythology in later works, including The Stairway to Heaven (1980) and The Wars of Gods and Men (1985). In The End of Days: Armageddon and the Prophecy of the Return (2007), Sitchin predicted that the Anunnaki would return to earth, possibly as soon as 2012, corresponding to the end of the Mesoamerican Long Count calendar.

Source: Anunnaki Origins