Try to Ignore the stilted narration and give this video a viewing.
I apparently am following in my late father's footsteps because he was obsessed with this stuff, albeit he came at it more from an Erich Von Daniken/Ancient Astronauts viewpoint—something I find increasingly unlikely. I do, however, find it very likely that our current civilization is not the first to harness high-technology and spread to every corner of the globe…and it doesn't require aliens at all.
People will say, "Okay, then…if there was a high-tech civilization that came before us, where are the remains of ancient cars, computers, helicopters, continental highways? What happened to them?" I have an answer for both those questions.
First, watch the series Life After People, which lays out exactly how short a period of time would need to pass before all traces of our civilization disappeared.
The oldest currently discovered human habitation, Gobekli Tepi in Turkey, dates to approximately 12,000 BC. If humans were to disappear from the planet through some natural or unnatural catastrophe today, 12,000 years from now the only things that would remain identifiable are the stone and massive concrete constructs (i.e.the Hoover Dam and Mt. Rushmore, and yes, even the pyramids, are examples). Archaeologists would find no cars, no computers, no helicopters. Our continental highway system would have crumbled to sand long before that amount of time passed. Even ships lost under the seas would have long since decomposed.
Grand, planet-wide civilizations could have conceivably risen and fallen several times over the last hundred thousand years that modern humans are believed to have existed.
But what happened to at least the one which immediately preceded our own? As I've written here before, research the Younger-Dryas event, a cataclys
And I'm not even saying that all those civilizations would use the same tools that we currently do. It would be very much like comparing apples to oranges. They might very well have used technologies we have no knowledge of yet (automatically implying alien intervention to some people), and no doubt used something other than petrol chemicals to power their world. (Because if they had, we would not have the supply we currently do if they had depleted them as rapidly as we have.) Likewise if we're wiped out, there will be precious little of those petroleum and its byproducts left to power the next civilization, forcing them to seek out other sources.
I'm not trying to convince anyone that this is what actually happened on our world, but give the video 30 minutes of your time and see what you think. Lord knows I can hear Ben's eyes rolling back up into his head when I'm watching this stuff, but it explains it for me, and a lot of the questions I've been asking since I was a child now have answers that make sense.