Many millions of years ago an advanced humanoid civilisation visited the Earth and settled there. They were called the Atlans and they established a cultural base on a great continent stretching from America to Australia, which they called Atlantis.
This explains the sudden appearance of Homo Sapiens in around 3 million BC and consequently, the dying out of Earth's indigenous population, as represented by the Neanderthals who could not compete with the new, more advanced race as it spread out from Atlantis to eventually cover the globe.
The Atlans had a two tier social structure comprised of the Priesthood and the People. The Priesthood were an aristocracy of genetically enhanced men and women, with powers that made them very much like gods - but without the immortality of the latter though they were reputed to live for two hundred years. The People, on the other hand, were as limited as Humans - and more so, following the cataclysm that befell Atlantis.
The original Atlan society established on the great continent of Atlantis was dominated by a triumverate of Priests, their names being Qualopec, Tihocan and Natla. The latter of the three, Natla, was cruel and despotic and plotted against the other priests in order to rule alone.
Note: This incomplete backstory of Atlantis is from an earlier version of Tomb Raider's storyline. It may or may not have occured in the final game - http://www.croftgeneration.com/eng/index.php?sec=tr1-prototype