Hmmmmm. So, I had an idea for the first ever PHWI which is short for Pre-Historic What If just now making a simple question that would have actually changed the course of our history as a species: what if we invented agriculture earlier? How would the earlier invention of agriculture affect the technological progress of humanity? How would society, economics and politics be affected? How would humanity as a whole be affected? Well, this is where you come in. So, what would have been if agriculture started earlier?
It's very hard to say because we don't really know why agriculture exploded across the world when it did.
My own bet would be that it was a combination of having a high enough population, pressure from rapid climate change and resource depletion.
Since higher human populations will drive resource depletion, arguably the way to get earlier agriculture is to raise the human population on the planet faster, forcing humans to move on from easy hunter-gatherer living and on to the hard graft of agricultural life sooner.
I really struggle to imagine how to get human populations higher sooner though. I had written a scenario for you based around "no Toba eruption 75kya", but when I did some searches to check details, it seems like there are serious questions over the
climatic effects of Toba or that a
population bottleneck even occurred at this point.
This article (summarized
here) shows a different perspective on when the bottleneck events were. According to this data (which may be being misinterpreted - this is a very new field of inquiry and we're still learning as we go), there looks to have been a bottleneck in all populations the examined between 40 and 20 kya. After the end of the ice age, human population boomed, probably reaching a total of around 5 million persons around 10 kya, when agriculture was being invented. It is really remarkable to me the way the graphs in Li & Durbin's paper show population shooting up rapidly exactly at the point when the ice age ends. This makes me think that even if the human population had avoided its earlier bottlenecks, it would not have zoomed up to the post-ice age 5 million mark, which makes me wonder if humanity absolutely needs a warm spell to grow enough to produce agriculture-friendly conditions.
If the population bottlenecks during the last 100 ky were somehow avoided (possibly impacting human evolution a fair bit but, um, let's just ignore that) and human populations slowly grow as they spread across the planet, my feeling is that the harsh climate and the absence of the violent climatic swings at the end of the ice age (where very favorable conditions were followed by harsh conditions and then again by favorable conditions in a very quick progression that only stabilized around the time the Bronze Age got started) would both put a ceiling on human population and mean that there would be an absence of crises forcing people to innovate. As such, I suspect that the most that could happen during the ice age is for humans to develop proto-agricultural gardening systems (where plants are not domesticated, but humans intervene to create gardens where favored plants grow together).
Then, as the ice age ends, human population would soar, and, go flying off a climatic cliff just as they did in OTL when the very favorable climate between the end of the ice age and the younger dryas ends and humanity needs to intensify their gardening during the cooler and dryer younger dryas.
But, while agriculture proper would begin about the same time in this scenario, the details would be very different. Likely, the human DNA pool has more contributions from other human species such as neanderthals, denisovians and homo erectus (since those populations would likely be made larger by whatever has helped Homo sapiens sapiens avoid OTL's bottlenecks). Likely, the pool is far more diverse generally (due to less bottlenecks and a higher population for a longer period of human evolution), likely leading to more resistance to epidemic disease. Likely, there would be even less in the way of megafauna around to tame. Horses, which were probably close to being hunted to extinction in OTL, won't be around. Nor will dozens of species of other animals. The pool of potential crops is probably larger with gardening having gone on for longer and having had time to spread more widely. This could well mean there are more centers of agricultural innovation as well.
Agricultural civilization would very likely advance more quickly in this scenario, though large empires may be much smaller, due to greater cultural diversity and the lack of horses.
fasquardon