It's a pity you didn't allow art, since there's hundreds upon hundreds of art pieces made by people from this period, including animals now only found much farther south.

But: stories it is. What we can do is talk about something that happened as a result of the African Humid Period ending.

Just to be clear, the change between wet to dry in the subtropics was because of the precession of Earth's orbit. The Earth "wobbles" on its axis so that where the Earth points moves in a circular fashion every 26,000 years. The particular orientation led to greater monsoons and the Green Sahara in question, but it was doomed to end. Because it is based on the Earth's direction the change was gradual by latitude, so monsoon levels started dropping from north to south.

Additionally, climate change was clearly abrupt in some local sites, although the exact nature of this is still a subject of research.

However, it isn't as if the moment the Green Sahara is declared ended in a particular place meant the climate just ossified in place. For Ancient Egypt and the Nile in particular we have historical knowledge about the level of discharge fairly accurately (try this figure) and you can see a drop from the "end" of the Green Sahara period all the way to the Old Kingdom.

The Nile keeps dropping during the Old Kingdom period -- that's when the Pyramids were built -- until finally hitting rock bottom roughly around 4200 BP (before present, so roughly 2200 BCE). This also is known as the Old Kingdom Drought, or more universally, the 4.2 ka event.

Now, there's some controversy here. I'm not going to argue about the global universality of the event, but I will say the science (using isotope ratios) is fairly firm about there being a Nile drought. And we definitely have narratives about that.

There's some Middle Kingdom texts of interest in this; Ankhtifi, one of the nomarchs or "Great Chiefs" of the Middle Kingdom has a text about a period where "All of Upper Egypt was dying of hunger, to such a degree that everyone had come to eating his children" -- and he goes on to explain how his nome (region) nobody went without hunger, and he was able to loan grain to others, even though people were like (locusts?) starving going north and south looking for food.

This feels like self-promotion and is also slightly out of the time span. There's also the well known Admonitions of Ipuwer or Ipuwer's Annals (depending which translation you use) written 800 years after the fact which discuss a collapse of the Egyptian monarchy with riots and looting...

See now, things are done that never were before,

The king has been robbed/deposed by beggars/rabble.

See now, men rebel against the Uraeus Serpent,

The disintegration of the country through fighting:

See now, fire has leaped high,

Its flame will attack the land's foes!

Men stir up strife unopposed.

See, the land is tied up in gangs,

The coward is emboldened to seize his goods.

...with dipping hard into sorrow.

If only this were the end of man, no more conceiving, no births

But since giving birth is desired, grief has come and misery is everywhere.

So it is and will not pass, while these gods are in their midst

While science backs up a drought, archaeology does not necessarily back up events so extreme, but again, if we're simply on the lookout for folklore on what things were like at the disaster of the Nile, maybe it doesn't matter if it was real.

Perhaps the most interesting text -- as it claims a ruler from the actual Old Kingdom -- is one that, oddly, was made much, much, later. It in fact dates to the Ptolemaic Kingdom (332 to 31 BCE) but the text, known as the Famine Stela, claims to be in regards to pharaoh Djoser, 3rd Dynasty, he of the famous step pyramid, a stepping-stone (ahem) of sorts to the Great Pyramid.

I was in mourning on my throne,

Those of the palace were in grief,

My heart was in great affliction,

Because Hapy had failed to come in time

In a period of seven years.

Grain was scant,

Kernels were dried up,

Scarce was every kind of food.

Every man robbed his twin,

Those who entered did not go.

Children cried,

Youngsters fell,

The hearts of the old were grieving;

Legs drawn up, they hugged the ground,

Their arms clasped about them.

Courtiers were needy,

Temples were shut,

Shrines covered with dust,

Everyone was in distress.

In short: there was a famine of great length, and Djoser inquires with priests where the god of the Nile is born. He is told of a sacred spring at a temple of Khnum. The high priest Imhotep goes to the temple and falls into a dream:

I am Khnum, your maker!

My arms are around you,

To steady your body,

To safeguard your limbs.

I bestow on you stones upon stones,

That were not found before,

Of which no work was made,

For building temples,

Rebuilding ruins,

Inlaying statues' eyes.

The story ends with Khnum's temple being rebuilt, causing the drought to end and the Nile to flow mighty once more.

It was written more than 2,000 years after the events (and "seven years" is suspiciously similar to the analysis of Pharaoh's dream in the Bible by Joseph). It is still faintly possible it was copied off an earlier preserved text; again, even if entirely written after the fact, it suggests a strong memory of the Nile being depleted at the end of the Green Sahara, long after the events occurred.

...

De Menocal, P. B. (2015). End of the African humid period. Nature Geoscience, 8(2), 86-87.

Middleton, G. D. (2017). Understanding collapse: Ancient history and modern myths. Cambridge University Press.

Nicoll, K., & Zerboni, A. (2020). Is the past key to the present? Observations of cultural continuity and resilience reconstructed from geoarchaeological records. Quaternary International, 545, 119-127.

Sołtysiak, A., & Fernandes, R. (2021). Much ado about nothing: assessing the impact of the 4.2 kya event on human subsistence patterns in northern Mesopotamia using stable isotope analysis. Antiquity, 95(383), 1145-1160.

Sadly, while these two events (Saharan desertification and Mesopotamian literature) happened somewhat nearby in time, desertification was basically done once Mesopotamians started writing literature ca. 2400-2000 BCE. And when they did record things, it's usually local history and only mentions foreigners if they invade or are invaded.

Pastoralism restructured societies across the Green Sahara ca. 6500-5000 BCE through destroying, incorporating, or converting Saharan foragers. Pastoralists would flourish for thousands of years across Africa but living in the original Saharan heartland became more and more difficult after 4000 BCE.

Desertification of the Sahara

By 4000 BCE lots of the Sahara had dried, turning from woodland into scrub savannah.^1 Then the 5.9 Kiloyear Event occurred (ca. 3900 BCE) which meant increased landslides, cave/shelter roof collapses, aeolian sand, erosion, and lakes drying out.^2 At Gilf Kebir (at the border of Egypt, Sudan, and Libya), pastoralists lived there ca. 4400-3500 BCE when that region had seasonal winter rains. This at least created pastures for the spring and summer, but once this regional season ended ca. 3500 BCE the pastoralists left as well.^3 A new sacred-building cultural trend swept the Sahara at the end of the 4000's BCE of building cattle burials. At Djabarona 84/13 in Wadi Howar (northwest Sudan) in the early 3000's BCE archeologists found 1000+ pits filled with cattle bones and relatively complete pottery. This cultural trend is suggested by Savino di Lernia to be a response to a changing climate - ritual innovation as divine appeasement.^4

The great eastern Saharan pastoralist center of culture had been Nabta Playa (southwestern Egypt): featuring cow burials, cemeteries, and an astronomical stone calendar. But this site was abandoned along with the rest of the eastern Sahara by ca. 3500 BCE,^5 and the central Sahara was mostly depopulated ca. 3000 BCE.^6 Although it's notable that remnant groups at Uan Muhuggiag (central Libya) survived til ca. 1600 BCE.^7 But in general, 3500-3000 BCE is considered the end of the Green Sahara period (The African Humid Phase).^8 The rock art styles at Gilf Kebir and Jebel Uweinat are considered done by ca. 3000 BCE.^9 But just because a region's culture declines, doesn't mean it's completely destroyed - Jebel Moya in Sudan was a pastoralist site still occupied in the Ptolemaic and Roman periods (ca. 300 BCE onward).^10

But mostly people fled as the Sahara dried. Pastoralists would go south-west into Mali and Mauritania and form Dhar Tichitt culture ca. 2500-2000 BCE.^11 Pastoralists would go east, spreading to the Lakes Region of east Africa, building megalithic sites and cemeteries around Lake Turkana (Jarigole, Lothagam, and others). This shockwave of pastoralists would take thousands of years to eventually reach southern Africa as they appear there ca. 500 CE.

The more-settled agro-pastoralists who lived along the Nile at the absolute eastern edge of the Sahara simply continued doing what they had been doing throughout the 3000's BCE: focusing on settled agro-pastoralism...along with getting more politically hierarchical. As Egalitarian societies like at Nabta Playa disbanded, pastoralists there probably fled to the Nile valley.^14 Perhaps integrating with local A-Group culture people there or moving to regional neighbors like the Naqadians of Upper Egypt, or other hierarchical pastoralists of Upper Nubia (like Kedada). By 3500 BCE, what surrounded those egalitarian pastoralists at Nabta Playa likely had an impact on their dissolution - they were bordered by powerful settled-agro-pastoralists just to their east - The Naqadians of Upper Egypt, the Kedada site in Lower Nubia, and A-Group people centered at Qustul in Lower Nubia. Only a few hundred years later ca. 3100 BCE, the 1st Dynasty of Egypt would form...ushering in the era of Near Eastern bronze age royal stately-empires.

Desertification became widespread throughout the Sahara ca. 2500 BCE onward,^12 which is precisely the flourishing of Old Kingdom Egypt and Mesopotamian cities who also around that time started writing, though texts from this period are sparse excepting cylinder hoards. All of this is only known through archeology and sometimes oral histories, and none of these Saharan events are recounted in Egyptian nor Mesopotamian histories from the bronze age, sadly.

One of the most interesting aspects about this period is mentioned by Katie Manning, that the Dhar Tichitt culture of Mauritania ca. 2500-2000 BCE used domestic non-shattering pearl millet. They had artificially selected this from their stock of domestic shattering pearl millet (which was more annoying to process), an artificial selection process that took ca. 500-2500 years: implying that the Proto-Dhar Tichitt (western Saharan pastoralists) had a kind of domestic pearl millet ca. 3000 BCE or earlier in that millennium. This is fascinating, because nearly on the other side of Afro-Eurasia...the Indus River Valley culture (a.k.a. Harappan Culture) of the late 2000's BCE had by that time imported African millet.^13 How the millet got there is a tough question, but obviously through Near Eastern trade via Mesopotamia via Egypt. Presumably in the 2000's BCE, other millet-using eastern Saharan pastoralists had got their domestic millet into the Egyptian market which went onward eventually to India.