A long, embarrasing time ago, Chet once posted a thread that recieved very, very little attention:
There were a few issues with the original post. The first was that there was an awful lot of hand waving. The second was that there was very little extrapolation of the consequencesof his proposed changes to the TL.
But it is still an intriguing idea!
Let's make it work. Or at least try.
No matter what we do, because of the time frames involved we're going to get a very different TL. I think it's best to not destroy humanity in the process so that we have some sort ofhistory and keep the whole shindig on-topic.
Modern man seems to date from about 200k years ago. That's a long, long time from the civ POV. The arisal of modern man puts an ancient TL bounds on when we can start this process moving faster. I'd rather have it take place at about the 75k yo range since that's the beginning of somemajor toolkit changes. We'll see if that works.
The mechanism is that we move (here's my handwave, smack it if ya like) one of the hotter hotspots from southeast of africa in the mantle to under the East African Rift Valley. We'll assume that we get the upperbounds of rift spreading(13 cm/year) with the extra heat.
The Somali Plate can move southeast 26 km if we use the 200k year start point. We only get 9 3/4 km if we use the 75k year start point. I'd say we're out of luck for going with a Middle Paleolithic PoD then. Even 26 km isn't that much and the resulting channel, if its there, willprobably be only 10 km wide at best.
There's probably not that much difference in fauna or flora. 10 km of shallow - 155m deep or less - gulf make it more like the Bosporus than the differences between Arabia and Africa. The shoreline between Africa and East Africa is more in common with Crimea than something on the Med North African Coast...but stretching for very, very long distances. The climate is prolly not that different from now, but then we have a very warm and shallow sea that stretches from the Gulf of Aden to almost Madagascar. This might get interesting climatic effects. The tides might be less, but with the warm water we might get some nasty currents. Warm and shallow, we might find this sea - the Olduvai Sea? - to be rather fertile.
There will be some intersting consequences of this spread though for historical purposes: there would either be no Nile or a much reduced Nile. So! There's probably no *Egypt arising. However, I don't think that there's much difference in where Civ is going to arise elsewhere though: The Middle East, Ganges, and Chinese Rivers are likely to be the cradles of civilization still. It's just the *Nile that might get jipped. I don't think that we'll see anything arise here that's a First One civilization, but once the others start ship building, something may take root on the northern tip of the Great East African Island. The diseaseenviroment is not going to be improved much, I think. :)