300,000 or a million. It's still not believable that man was smart enough to use tools but not smart enough to realize that plants grow from seeds and start planting what he liked.
um,...15,000 years ago, it wasn't a desert.
Early man lived as hunters and gathers. Many people still live that way. It has nothing to do with smarts.
About 15,000 years ago, some enterprising homo sapiens decided that they might try living in one place permanently and see how it worked out. It really caught on and remains the popular choice even today.
It would be hard to miss. First of all, people would chew on all kinds of plants, roots, seeds, berries; some would be tasty enough to look for on purpose like a bear that prefers a particular brand of beer. This time of the year there are seeds flying everywhere on the breeze. If nothing else, children sometimes play with some seeds. It would be no trick to gather some seeds and keep them over the winter rather than eat them and then notice that they sometimes start to grow and become the same kind of plant. You would have to go out of your way to not notice.
Read this book and then get back to us:
It examines the factors that influenced the discovery and spread of agriculture, writing, animal domestication, steelmaking, nationstates, and so on. It does an excellent job of explaining why these developments occurred at certain times and places, and not others.
As for agriculture, the condensed version is that kickstarting an agricultural society from scratch is a lot harder than it sounds, and at the beginning the future benefits don't look all that great compared to the amount of effort and risk involved. Plus, only a few places on the planet had both a suitable climate, *and* a suitable mix of adaptable crops (and domesticatable animals), to make it possible to subsist on a reliable, steady, nutritionally workable agriculture.
Yet another hurdle is the fact that in their original natural form, even the best of today's crop plants (e.g. wheat, corn, etc.) were barely suitable for use -- it was only after thousands of years of selective breeding (first by accident, later on purpose) were they eventually refined into crops that could truly sustain farming communities.
Figuring out that you could plant seeds and make something grow was the *easy* part, and was undoubtedly recognized for tens of thousands of years before the first real "farming community" managed to make a successful go of things after solving the many other obstacles involved.