In chapter 6 of Guns, Germs, and Steel, "To Farm or Not to Farm" (p. 111), Jared Diamond says that primitive harvesting tools like flint blades and grinding slabs
were prerequisites to the planting of cereals as crops. These cumulative developments constituted the unconscious first steps of plant domestication.
How could these tools possibly have helped humans domesticate plants unconsciously? What are some examples to support Jared's case?
The start of the sentence, which you have excluded from your quotation reads 'All these techniques, though developed for the exploitation of wild cereals,' I think this is important context.
The techniques and tools were developed to harvest, store and process wild cereals. But, as there would be no point in planting crops if you did not already have the means to harvest, store and process them, those tools and techniques are prerequisites for arable farming, i.e. 'something that must exist or happen before something else can exist or happen'.
So Jared is saying that domestication of plants could not happen without early humans already having the understanding and the means to process the crops.
I don't think Jared means that humans domesticated plants unconsciously, but that having the skills they would need to maximise the benefits of doing so, was a step which brought them closer to that domestication, although it was not taken with that intent.
NB: If anyone is wondering where the ‘history’ is in this answer, it was made when the question first appeared in Literature SE and was migrated with it!
Flint blade is needed to collect the grains from plants. A grinding slab is needed to make flour from those grains. Which means that humans learned to make some kind of bread.
Citing the book "After the Ice", from Steven Mithen:
The key difference between wild and domestic varities [of grain] lies within the ears of grain. In the wild forms these are very brittle, so that when ripe they spontaneously shatter and the grain is scattered on the ground. Domesticated forms do not do this; their ears remain intact and the grain needs to be removed by threshing. So without human management the domesticated forms cannot survive, as they are unable to reseed themselves.
Which means, domesticated grains wait for the harvester.
Hence, the unconscious first steps of plant domestication is that humans had to select the grains that riped later, because the ones that shattered earlier where already in the ground. Those grains that humans collected where later used as the seeds for agriculture.
After several generations of bread making, the plants human had where the ones that needed manual labor to obtain the grains.
All these techniques [e.g. flint blades, grinding slabs], though developed for the exploitation of wild cereals, were prerequisites to the planting of cereals as crops.
Buy a new tool for a handyman or a cook, and just watch how many ways they find to use it during the initial period of newness.
Abraham Maslow summarized the Law of the instrument as:
I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.
Or, as Abraham Kaplan said:
Give a small boy a hammer, and he will find that everything he encounters needs pounding.
Consider what happened in the development of agriculture.
Yes, it sounds backward, but it wasn't the desire for more food that inspired agriculture, it was the desire to use existing tools.
