There are absolutely some huge unknowns out there. Here's one that fascinates me: The earliest evidence for crop domestication around the world all happen within roughly 1-2k years of each other. Hundreds of thousands of years of foraging, and all of a sudden agriculture evolves independently half a dozen times in that tiny span. We've spilled libraries worth of ink on the subject, but pretty much the only firm conclusion we have is that there wasn't a singular cause.

There is a [paraphrased] saying that might explain your friend's reactions though: the most exciting thing in archaeology is your data, the most boring is someone else's data.

We have to compartmentalize a lot because there's an overwhelming amount of stuff out there.

Heh, that's a good reaction. :-)

Maybe I don't know the problem well enough, but the relatively simultaneous nature of domestication seems like less of a mystery to me. More recent domestications (eg. in the Americas) seem to indicate that a hunter-gatherer population needs to be getting comfortable with a particular bioregion for at least a thousand years or so before an accumulation of of local knowledge can lead to the development of decent local cultivars. If this is a general and defensible rule, then I think our climate history can provide the rest of the evidence.

The ice age wasn't just cold, it was also chaotic, with temperatures pinging all over the place from year to year:

https://www.nature.com/scitable/knowledge/library/abrupt-cli...

In that context, any population would have had difficulty staying in one place for a thousand years -- I don't mean living a settled life, I just mean hanging out in generally the same bioregion. Bioregional adaptation would be detrimental in such an unstable environment: your tribe needs to stay mobile and highly adaptable, or it'll die. No chance to develop agriculture under those circumstances.

Eventually we enter a nice calm interglacial period, and settle down to do some fishing -- then spend the next thousand years being chased around by rapidly rising sea levels and mega-floods from bursting glacial dams.

Finally, about 11k-10k BPE, all that settles down -- although not without us acquiring some nice flood myths along the way -- and we have time settle down and start getting to know some bioregions on a long-term basis. A thousand years or so later, we've got agriculture popping up all over the place.

Seems like a reasonable story? Or am I missing something?

It's not bad as a first idea, but there are a couple difficulties with it.

1) We know sedentary hunter-gatherers existed throughout the upper paleolithic. This is a bit of an under-researched area for various reasons, but we know they definitely weren't all mobile.

2) Humans had been continuously inhabiting areas in east Africa since even before they could be called anatomically modern. Yet, agriculture there emerged at roughly the same time as elsewhere.

3) The earliest agriculturists were semi-sedentary anyway, not predominantly sedentary and fixed in place. How mobile they were depends on where and when we're specifically talking about, as it varied over time.

4) Climatic variability in New Guinea (another early center of agriculture) actually increased during/after the younger dryas.

This one's a bit unfair, as it's outside the scope of what I originally said. Nonetheless, it'd be nice if we could also use our explanation to say things about independent domestications long after the start of the holocene, like the eastern agricultural complex.

I'm defending a thesis I haven't thought about too much, but just to play devil's advocate, I'd say:

1.) Interesting about sedentary hunter-gatherers during the upper paleolithic -- I'd like to know more about that! But my argument would be that even if the the people were settled, the climate wasn't -- and that the severe climatic fluctuations which were happening would have been enough to deter the incremental steps towards agriculture.

2.) I presume Africa would have experienced the same climatic fluctuations as everywhere else. This begs the question of why they didn't develop agriculture 120k BPE, during the last interglacial? I'd argue it's because we still had some evolution to do to become behaviorally modern, around 80k BPE. So this interglacial is really our first time at-bat with a stable climate.

3.) True, but if they passed through the same bioregion/climate at the same time every year, then that's enough of a fixed point to begin experimenting with agriculture. My theory is as much about the mobility of the bioregions/climate as the people.

4.) Could be a counter-argument indeed. I know too little about New Guinea, which is a crazy fascinating place. I know that there was very early cultivation there, which was also abandoned some thousands of years ago. Don't know how that relates to its history of climate stability. Do say more?

Climate. We know from ice cores that the climate prior to the current interglacial period wasn’t very conducive to crops. It was dryer and had less CO2. 180ppm be 260ppm pre-industrial area.

Lower CO2 levels meant that plants lost more moisture opening their pores and growth would be stunted.

Climate change is a big part of the puzzle, but for cases like the cucurbitaceae family in the Americas, it likely also reflects quaternary extinction events and social/behavioral changes in human populations, among other things. It's complicated and multifactorial.

> ziggurats are just an inevitable step in the development of urban architecture (this is definitely untrue).

Are you sure? I'm not strongly in one camp or another, but it seems relatively intuitive that if you are stone age people and want to build something tall, a square-based step-pyramid is the most stable form that can rise relatively fast wrt to the amount of material used and work needed

Of course this only pushes back the question of _why_ did all these people want to build tall things roughly at the same time, but still

Defensibility. Hill forts have been around as long as settlements. Don’t have a hill? Build one.

i dont know i think your thinking implies years of growing with the same theories, like getting to a point of building with square like objects i dont think its a given

> in sites separated by thousands of miles, with no possibility of communication between them

Human walking speed is about 3.1mph. Walking 8 hours a day, it takes 40 days to cross a thousand miles. Communication's slow, but not that slow – especially if you've got horses. My working theory is that people walked.

Across the ocean? The walking theory breaks down when you look at the development of the Americas. That actually almost certainly kills any theory that communication is required. At least in the Americas, the timing was surely a coincidence?

From what I've heard, transatlantic boats can be fairly small and rudimentary.

Not really. The Vikings pulled it off, but it was hardly a walk in the park and required a network of bases in Iceland, Greenland and elsewhere to support venturing further.

I was thinking of the leather coracles used in another voyage. I read this book: https://www.goodreads.com/book/show/1088116.The_Brendan_Voya...

There is evidence that some Pacific Islanders made it to the coast of South America in very small craft.

doesn't look like anything to me