(For a book) - how was the process of grain-threshing carried out by neolithic (or similarly primitive) tribes? I know that there are still modern methods of doing it by hand - would they have been similar back then, for example beating the grain in a rawhide sack or something like that? Do we have any evidence of tools that may have been used to thresh?
Probably the earliest tools for de-husking grains were the same as tools used for grinding grains. De-husking is the process of applying force between two hard objects until the husk cracks, and then it falls off after some rubbing. You can do this simply by pounding grain (lightly) between two stones.
This history goes back a lot further than farming. People were harvesting grains for food many tens of thousands of years ago. There are 30,000 year old grindstones with flour residue on them, showing that people were processing grains at least that far back.
The technique is to simply pound the grain between two stones, using a light amount of force to begin with. Then you winnow the grain (just let it fall from a height and let the wind blow the chaff away), pound some more, winnow, repeat. As more of the husk is removed, you can pound a bit harder to remove particularly sticky parts and crush the grain a bit as well. They weren’t producing machine refined flour at the time, more of a crudely crushed grain like semolina. This is good enough for baking into flat pancakes over a hot rock, after proper hydration.
After people started farming and had access to larger amounts of grain, they probably used simple methods like spreading the grain on a hard surface and walking over it. You have to throw some hard objects like sticks among the grain, because de-husking happens when grain is crushed between two hard objects. Human feet are too soft - they simply provide the weight/force on the sticks to do the job.
After the domestication of cattle, the same thing could be done by walking cattle over the grain. You don’t need sticks for this because their hooves are already hard, and they weigh a lot more than a man. This method is still used in some parts of the world.
I’ve seen no evidence of beating grain in a sack. My understanding is that this comes from China, where it was used to de-husk rice. They would beat the sack with flails to thresh it. But rice de-husks a lot more easily than wheat, and way more easily than ancient grains like emmer or einkorn, so I’m not sure how effective that would have been for our very early ancestors.