I was taught in school that civilization is believed to have begun with the Sumerians around 6000 years ago. However after some quick research on my own it appears that a step pyramid has been found dating back to 22 000 BC, as well as several ruins falling into the 15 000 - 10 000 B.C. range. What does this mean for the current model of how civilization started? If a civilization 22 000 years ago could build a step pyramid, does this mean they probably had agriculture as well ? Were there many cities all over the world with distinct cultures that have been lost to the ages ? What would life have been like for people in this time ? Would we have had armies and "nobles" and merchants and trade routes ? 22 000 years ago, would it have looked like Sumeria but without the writing ? Does the existence of ruins from 20 000 B.C. lend credence to stories of Atlantis and other lost civilizations? What exactly do we know about this enigmatic period in human history?
It sounds like you may have stumbled upon some pseudo-archaeology articles. The oldest monumental construction that we have is from the site of Göbekli Tepe which dates to the 10th millennium BC. People were certainly around long before then and had their own cultures, but they were somewhat different as these people were hunter and gatherers and did not construct monumental works like step pyramids. It's very unlikely there are any advanced "lost" civilizations because we just don't find the material culture associated with it. We've got stone tools that date back a couple of million years ago and can see the general progression from there to the present. Sure, there may be some gaps in areas, but those gaps are not going to be filled by anything as out of the ordinary as a lost advanced civilization.