Earth Log 0017 Out of Africa

We left the previous entry at a gate. Our species had existed for something like a quarter of a million years, almost all of it inside Africa. It had pressed against the northern exits more than once, during the wet intervals when the desert greened, and each time it had fallen back, leaving no lasting line beyond the continent. Then, sometime around seventy thousand years ago, the corridors opened again, and this time the people who passed through kept going. Everything in this entry follows from that crossing.

A word on the gate itself, because it has been argued over for decades and the honest answer is that we do not know which one they used. There are two natural exits from Africa toward the rest of the world. The northern route runs through the Nile valley and across the Sinai into the Levant — the same land bridge by which the earlier, failed excursions had reached Skhul and Qafzeh. The southern route crosses the narrow mouth of the Red Sea at the strait of Bab-el-Mandeb, where, at times of low sea level, only a few kilometres of water separate the Horn of Africa from Arabia. Both routes have their advocates and their evidence, and it is entirely possible that the truth involves both, or that the distinction matters less than the arguments suggest. The previous entry deliberately left this question open, and so does this one. What matters is not the precise doorway but that, this time, the people who passed through it survived and multiplied on the far side.