"Agriculture would not have been attractive, and was probably taken up when population pressures depleted ready supplies and forced people to begin to grow their own food or starve."Agriculture would have started just as soon as someone ran out of something like watermelon that they wanted more of.
Besides, how long would it have taken for population pressures to mount? Assuming the population doubles every 100 years, in 2000 years (50 generations) you have 2 million people. In 4000 years (100 generations) you have 2 trillion.
Populations don't double every 100 years. Indeed, prior to a couple of hundred years ago, it took forever and a day for the population to double.
Historical Estimates of World Population
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