[Carry_Okie]

History, technically speaking, means recorded human history, so in practical terms, I was talking about stone age through modern Egypt, at least prior to the Aswan dam.

I found the file. The capture of the White Nile into what is now the Nile was in approximately 8,000 BC.

That's borderline "history."

My source is:

Subsurface Valleys and Geoarcheology of the Eastern Sahara Revealed by Shuttle RadarAuthor(s): J. F. McCauley, G. G. Schaber, C. S. Breed, M. J. Grolier, C. V. Haynes, B. Issawi, C.Elachi and R. BlomReviewed work(s):Source: Science, New Series, Vol. 218, No. 4576 (Dec. 3, 1982), pp. 1004-1020Published by: American Association for the Advancement of ScienceStable URL: http://www.jstor.org/stable/1688710.

[yefragetuwrabrumuy]

It still returns to my original point, that for the vast majority of the rise of Egypt as a civilization, the Nile provided an annual flood, which was followed by a single harvest.

This necessitated food storage for the rest of the year, but if it was a successful harvest, also meant that the rest of the year could be used for other things.

However, if in the early part of their rise, there was warmer, wetter conditions, caused by global warming, it might have given them a smaller, secondary growing season, and a food surplus that could be sold, bringing in great wealth.

Yet with the onset of cooler weather, there would be no extra rainfall, and the land outside of the Nile flood region would dry out.

“By 7,000 years ago (5000 B.C.) and lasting for about four millenniums, the earth was warmer than today, perhaps by 4 degrees Fahrenheit... Although the climate cooled a bit after 3000 B.C., it stayed relatively warmer than the modern world until sometime after 1000 B.C., when chilly temperatures became more common.” - Stanford

[gleeaikin]

Sounds as if that shift may have occurred at the end of the Younger Dryas, with changed climate conditions.