20,000–15,000 BCE: (The Last Glacial Maximum as the Catalyst for Grain Harvesting in the Horn of Africa — Widely Drier Climates Across Africa Causing Foreste…

20,000–15,000 BCE: (The Last Glacial Maximum as the Catalyst for Grain Harvesting in the Horn of Africa — Widely Drier Climates Across Africa Causing Forested Areas to Shrink and Grassy Areas to Expand Especially in the Northern Ethiopian Highlands, Whichever Society First Began to Harvest Wild Grains Gaining a Productivity Advantage That Would Have Allowed Population Growth and Expansion into New Territories, and the Sickle-Shaped Stone Blade with Grain-Harvesting Sheen as the Diagnostic Archaeological Marker of This Economy): The adoption of grain harvesting in northeastern Africa was most likely a response to the climate changes of the Last Glacial Maximum, which peaked in the twentieth millennium BCE. Widely across Africa the climates became significantly drier during this era. The effects in the Horn of Africa would have included a shrinking of forested areas and a great expansion of grassy areas, especially in the northern Ethiopian Highlands. Faced with this kind of climatic challenge, whichever society first began to harvest wild grains from the newly expanded grasslands would have gained a productivity advantage in their subsistence over other nearby foraging peoples — an advantage that would have allowed their population to grow and expand into new territories. This is the mechanism that drove the initial expansion of the Afrasian family: not conquest, not migration for its own sake, but the competitive advantage conferred by a new subsistence strategy in a changing climate. And there is a diagnostic archaeological marker for this economy: a small, sickle-shaped stone blade with a particular surface feature — a kind of sheen caused specifically by the cutting off of grain stalks. These blades survive well in the archaeological record, far better than the grains themselves. Where you find sickle blades with grain sheen, you find grain harvesters. And when you find them in the Horn of Africa at dates consistent with the Last Glacial Maximum, you find the proto-Afrasian people themselves — the ultimate ancestors of the ancient Egyptians, harvesting wild grain in the Ethiopian Highlands twenty thousand years before the first pyramid rose on the Giza plateau.