Conventional wisdom says civilization – writing, agriculture, buildings, cities – is geologically recent, only a few thousand years old. But how do we know that? What if civilization is actually tens or hundreds of thousands of years old, and there were castles and knights in what we now call the Stone Age? Of course, this might not be the case, but it seems like an interesting possibility. Consider that:

– We know, from fossil evidence, that modern humans appeared several hundred thousand years ago. That’s a long time to develop civilization and culture in. And ancient people weren’t stupid; Neanderthals actually had larger brain volumes than modern men.

– The farther back we go, the fuzzier evidence about a civilization gets. If a particular type of data (eg. metal artifacts, or written documents) has a half-life of a thousand years, then we have a lot of information on last year, but little on two thousand years ago. In twenty thousand years, everything is lost.

– Much of our knowledge of past technology levels – even the recent past – depends on single data points. Famous examples are the Antikythera calculator of ancient Greece, and the movable type of Minoan civilization. Hence, for even older civilizations, it seems likely there are zero data points – we just don’t know anything about their technology.

– Until very recently, virtually all cities were on rivers or coasts. Water makes trade, agriculture, moderate climates, and other important things possible. However, over geological time, rivers and oceans shift around. In particular, at the end of the last Ice Age, sea levels rose several hundred feet. Any cities before then have long since been drowned, and exploring under oceans is extremely difficult.

– The oldest cities we do know about – Egypt and Mesopotamia – are in the middle of deserts. Are deserts, even with rivers nearby, really the only place for cities? Maybe, but it seems strange. On the other hand, we do know deserts are exceptional for preserving historical artifacts, as the dry conditions slow rot, rain, and other forms of damage. Even though most Romans were European at the height of the Roman Empire, Egypt is actually the best source for Roman documents – any Roman documents in Rome have long since rotted away. What if other European empires developed earlier, and we just can’t find them?

– We still don’t have definitive proof of when people colonized the Americas, or what native populations were pre-Columbus. Hence, we know it’s possible for people to inhabit a wide area for thousands of years, without leaving any conclusive evidence they were even there. And we know it’s possible for even very recent civilizations (a few hundred years ago) to have their population unknown to within a factor of four or more.

– Metallic artifacts – gold, silver, copper, bronze – have always been considered valuable, as they can be sold and re-melted. (King Tut’s tomb was notable for being virtually the only one with lots of gold jewelry left; all the others were heavily plundered.) Hence, the “Stone Age” might come from stone artifacts being artificially over-represented (compared to metallic artifacts) the farther back one goes.

(Disclaimer: I’m not a historian, and there may well already be evidence refuting this idea. Comments from those with relevant expertise welcome!)