[lumost]

To what extent is our understanding of this period limited by survivorship? Granite doesn't weather significantly, so we see lots of metalithic stone structures with ambiguous dating. The near east had significant changes in inland climates so we find ancient cities that were not built over there. Soft rock/mud Brick structures can survive in dry climates - so we see evidence of the oldest civilizations in deserts.

Colonial New England barely exists outside of active preservation attempts.

[AlotOfReading]

Short answer: it's hard to fully say, but most people believe that the holocene is a lower bound on this sort of thing. I'll try to explain, but keep in mind that I'm trying to massively simplify a huge field of open questions.

The fundamental assumption underlying most archaeology is that changes in material culture broadly reflect people reacting to the world around them in intelligent ways. Most archaeologists therefore believe that Pleistocene people didn't build permanent structures out of stone because nomadic or seminomadic lifestyles were more optimal for the chaotic pleistocene environments happening globally. There's a few people who disagree with the universality of this idea, most famously the authors of Dawn of Everything who argue for a more diverse family of lifeways in early humans, but that's just quibbling about the edges of this overall narrative rather than rewriting it.

And we'd expect to have more evidence than we do if the holocene boundary wasn't the effective start date for this kind of structure. Cave environments are much more stable, and it's where much of our evidence comes from. Gobekli Tepe (GT) and other Tas Tepler sites are made with local limestone, an extremely erosion-prone rock. We have sites covered by existing urban cities like Jericho, the earliest layers of which date from around the same time as GT. We also have older structures, like the epigravittean mammoth huts, and a fairly good idea of the forager->farmer transition in the near east across the natufian culture. GT is actually thought to be part of that transition.

But yes, a lot of organic stuff from the pleistocene is gone. Organics were probably the dominant form of material used, so that leaves a huge gap we're still struggling with. Not really sure where I'm going with this, so I guess I'll stop here?

[nemomarx]

Thank you for this thoughtful explanation

Do you think recent findings about early human sites on other continents (Americas etc) change any of this, or does that still mostly fit with our understanding? My layman's knowledge is that the exact date of when people reached certain landmasses shifts around based on new evidence but I'm not sure if that's an important part of the timeline generally

[AlotOfReading]

No, those are different topics. The current evidence for the initial peopling of the Americas is particularly problematic because we don't have a great narrative for how those dates could work.

[biotinker]

> Colonial New England barely exists outside of active preservation attempts.

As someone who grew up there, this isn't really true. It's more that buildings have been upgraded/replaced over time by choice, resulting in a sparse patchwork of old buildings rather than large old cities. Places like the Wayside Inn[0] predate the country by a century, and have been "preserved" only because they have more-or-less continuously operating as an in since 1686.

The New England climate isn't all that different than the original England. I think the cultural and legal climate around old buildings is more impactful here. I would be curious to know about the comparative longevity of 17th-century wooden buildings in Europe.

[0] https://en.wikipedia.org/wiki/The_Wayside_Inn_%28Sudbury%29

[gerdesj]

Some years back an aunt and uncle owned a cottage in Devon (near Exeter) with 1649 carved into the wall by the front door.

Cottages like that had a simple timber frame and cob walls, which is only a slight improvement on wattle and daub! Cob is mud and straw and a few binding agents and traditionally: horse piss to act as an accelerant to aid setting or something. Floors are joist and boards. The roof is thatched, often with a "cat slide" and foundations are laughable.

The thatch needs replacing something like every 25-50 years. Cob needs patching, especially if the roof leaks (not replaced on schedule) and it starts rotting. However all this stuff happens gradually and it can be repaired gradually too in most cases, as and when you like and within budget.

A concrete structure ... let's say Charles Cross multi-storey car park in Plymouth ... well hello concrete cancer! OK this is a bit different to the cottage but let's see how the "modern" world has progressed with a building material that was used by the old Romans and likely before.

A concrete beam on its own is "quite" good as a supporting material. Conc is superb in compression and quite good in tension. In a horizontal beam when you put a load on it, the top will be compressed and the bottom will be in tension. Think about a wide thin rectangle and imagine pushing down on it. Imagine it bending into a U shape - the top side will be compressed and the bottom will be stretched (tension). That's a fairly simplified model!

Now, cast your concrete beam around a long steel bar and put nuts and washers on both ends and tighten them so that the entire beam is in tension. There are other methods to do this but this is easier to envision.

Now you have locked in a lot of energy into the system. The upside of "pre-stressed" concrete is that a given beam ("member") cross section can carry a lot more weight than a non pre-stressed member. The down side is that deliberate demolition is really hard and non deliberate demolition is possible.

So, that concrete cancer thing. Conc cancer is caused when salty sea air and moisture (rather likely in Plymouth) permeates conc made from Portland cement. Its more complicated than that but the sea salts are key. The conc gradually degrades in a rather strange way - map cracking and a gel develops in the cracks (I think, I studied this stuff quite a while back). The usual conc matrix ends up with weak lines running through it.

Anyway - you have energy locked up in members and those members are failing. Boom!

There is a lot to be said for old school materials and practices.

[physicsguy]

These almshouses are near where my father lives, and are fairly unremarkable: https://historicengland.org.uk/listing/the-list/list-entry/1...

[WalterBright]

> cast your concrete beam around a long steel bar and put nuts and washers on both ends and tighten them so that the entire beam is in tension.

I think you meant "compression".

[throwaway173738]

The steel will be in tension and the concrete in compression.