The ice age itself would have had glaciers grinding down all evidence to nothing. Even our metal based structures would not withstand it very well over a few thousand years.
I agree that it doesn't make sense for there to be a single 6,000 year time period of human prosperity and collaboration, its much more likely that there have been multiple periods over a 200,000 time span. Perhaps some traits in humans continually set us back to a rudimentary lifestyle with thinned populations.
> Even our metal based structures would not withstand it very well over a few thousand years.
Well, not steel framed buildings or anything like that. But our modern civilization has certainly done things that I think stand a good chance of lasting hundreds of millions of years. Take for instance glass bottles. Those tossed into the ocean won't last more than a few decades before they're eroded to nothing (see: sea glass), but we've created so many glass bottles and distributed them so far and wide, it is virtually certain that many of them will survive in the soil for a very very long time. There is no doubt that glass can last for millions of years under the right conditions; there is a lot of volcanic glass around that attests to this. There are so many glass bottles in landfills or littered around the world, at least some of them are certain to be in geologically stable conditions.
Then there are things like mountaintop removal mining. Maybe normal quarries get filled in and hidden over time, but there's no hiding the top of a mountain being sliced right off.
Humans were not mass manufacturing things back then, and there were orders of magnitude less people.
On top of that, we don't even have exact knowledge of where to look. Most places we do discover have plenty of signs and evidence, they are just buried under 10ft of dirt and thus essentially undiscoverable.
> Humans were not mass manufacturing things back then
Ah, but how do you know that? You weren't there. ;)
Sometimes the absence of evidence really is evidence to the contrary, but other times it isn't. It all depends on whether or not it's reasonable to expect evidence to be found given the amount of looking we've done and the nature of the evidence we're looking for. If we don't find a ton of glass coke bottles in the soil around the world, after digging around in innumerable construction sites on almost every corner of the globe, that's strong evidence that nobody was mass manufacturing coke bottles 50k years ago.
Contrast that with the lack of evidence for ancient wooden sailing vessels. We don't have any evidence of wooden ships 50k years ago. But supposing there were a shipbuilding culture back then, would we really expect to find evidence for it? All those wood artifacts would be LONG gone, even the oldest bog wood ever found is less than 10k years old. In this case, the absence of evidence is weak evidence to the contrary at best.
Old things aren't necessarily that far under our feet. I've excavated 4,000 year old sites under a couple inches of dirt, and found 10,000+ year old artifacts on the surface.
Were that the case we'd have evidence of the "Material culture" of these cultures, yet we do not. Conversely, we have literally TONS of archaeological evidence of Neolithic hunter-gatherer people spread across the entire world during these so called "Lost ages" so personally I think it's preposterous to assume that somehow some advanced civilization that left absolutely ZERO trace of it's supposed grandeur existed beside a hunter-gatherer civilization for which we have plenty of archaeological evidence.
It's a certainly fun through experiment to think of some lost ancient civilization with glittering cities and high technology that was ground down to dust by the last ice-age, but there's literally no factual evidence to support such a notion and plenty of factual evidence to disprove it, so it's best not to get sucked too far down that particular irrational rabbit-hole.
Early civilizations did not appear out of nothing 6000 years ago. The earliest evidence of cereal harvesting in the Middle East is from 23000 years ago. The transition from hunting and gathering to sedentary farming communities took over 10000 years, and those communities needed thousands of years to grow into large sophisticated cities.
It's also good to remember that there has been an ice age for the last 2.5 million years. The climate is generally too cold and dry for agriculture, except during relatively short interglacial periods. Maybe there was an opportunity for a civilization to develop in the Eemian period 130k to 115k years ago, but that was likely the only window of opportunity.
Eh, that doesn't get you much. Glaciers weigh heavy on the minds of North Americans and Northern Europeans, but they didn't reach much further -- no civilization south of, say, 40N would be obliterated by the glaciers themselves such that we would expect no trace to remain today.
Sea level change would be a bigger global risk, but aside from sudden flooding, you would expect that to just push back an established civilization to the uplands of their territories rather than wiping them out root and branch.
The fact that civilisations tend to cluster near shorelines and waterways means that the impacts of sea level rise would likely be quite significant. Particularly at eliminating incidental traces of, say, groups or cultures migrating along such coastlines. I suspect virtually all of the early migrations of native Americans would be so affected, especially along the west coast of the Americas.
I agree that it doesn't make sense for there to be a single 6,000 year time period of human prosperity and collaboration, its much more likely that there have been multiple periods over a 200,000 time span. Perhaps some traits in humans continually set us back to a rudimentary lifestyle with thinned populations.