We have two established facts:
a. continents move over geological times due to tectonic plate action
b. proto-humans arose in Africa and over time populated six of the seven continents.
So my question: did continental drift affect the routes taken to spread population ie. make the routes shorter or longer.
Reported for forum change.
Welcome to the SDMB, syykre03!
We put different kinds of questions in different forums – ATMB is for questions about policy and logistics of the operation of the message board, so I’ve move this from that forum to General Questions, where it will get a better answer.
twickster, for the SDMB
[non-mod]My off-the-top-of-my-head guess would be no – continental drift happens in geological time, which is too slow to affect the lives of a single hominid generation, or even several hominid generations. I’m sure someone will be along soon with a better answer though.[/nonmod]
Not really.
The earliest humans to leave Africa were Homo erectus (or similar to it) about 1.9 million years ago. At this time the continents were mainly in their modern configurations. Homo erectus almost certainly migrated from Africa to the Middle East via the Sinai, which already existed at that time.
Later migrations by modern humans were affected by sea level change rather than by continental drift. Sea level was much lower during parts of the Ice Ages because so much water was locked up in ice. Humans probably colonized Australia around 40-50,000 years ago when the water gaps between it and Southeast Asia were much lower. And they were able to walk between Siberia and Alaska when the Bering Land Bridge was exposed before sea level rose at the end of the Ice Age around 13-15,000 years ago.
Great summary. But let’s take the OP from a slightly different perspective. Continental drift that happened before the evolution of the genus Homo affected the rate at which certain continents were populated. Since South America was once joined to Africa, both South and North America would almost certainly have been populated by early humans long before it was if continental drift had not happened.
Of course, one might argue that humans may never have evolved in the first place (or evolved sooner) if continental drift had occurred differently. Certainly shifts in weather patterns affected human evolution and those weather patterns would have be quite different had the continents been arranged differently.
But if we assume, for the sake of argument, that we can ignore that affect, then humans would have migrated to the Americas directly from Africa, and not through Asia, if continental drift had not separated S. America from Africa until the the time of H. Erectus.
But you’re just considering tectonic movements since the breakup of Pangaea. Africa and South America separated all the way back in the Cretaceous. If you are going to start with such a remote period, why not go back to some of the earlier supercontinents such as Rodinia about 1 billion years ago?
Of course, if plate tectonics did not occur at all we would not get mountain building or renewal of the crust. The continents would have all eroded below sea level long long ago and many of the elements that life depends on would be less available. Only aquatic life would probably be present.
Paleontologist Steven Stanley has postulated that the closure of the Isthmus of Panama about 3 million years ago triggered changes in ocean currents that caused Northern Hemisphere glaciation. This resulted in a drying trend in Africa that caused forests to retreat and prompted the transition from semi-arboreal Australopithecus to the fully bipedal Homo.
You see, it actually all started with the Big Bang. 
Interesting. It’s only been relatively recently, I think, that the partial aboreal behavior of Australopithecines, like A. afarensis, has become the consensus. When Donald Johanson first described that species, one would often hear: “chimp head on a human body”. But more and more evidence of a mixed way of life seems to be popping up all the time.
Stanley’s book is called Children of the Ice Age. Personally, I think that Stanley glosses over a lot of the evidence that is not in accord with his ideas.
Ah, yes. Read it years ago. Forgot the name of the author and that particular hypothesis.
Just clarifying…you are talking about well before ( i.e., 20k-ish years ago), right?
I think the mitochondrial DNA evidence showing increasing diversity of mtDNA lines as you progress south in the Americas strongly suggests colonization well before the last glacial maximum, with subsequent thinning of northern populations during glaciation, and re-expansion northward (in addition to any new post LGM arrivals from Eurasia).
I was speaking of the last time the land bridge itself existed (which may have been about 15-16,000 years ago), rather than the time that the human populations that first colonized the Americas became separated from other populations (which may have been about 20,000 years ago.) The earliest sites in North America for which there is now good evidence may date to about 15-16,000 years ago.
It should be noted that the land bridge was a dead end as far as further land migration goes. Yes, there was an ice-free corridor on the east side of the Rockies, but it wasn’t particularly conducive to travel by hunter-gatherers. Pretty much all of it had been covered by glaciers at one time or another, which leaves the ground barren.
Most likely, the rest of the Americas were settled by people who migrated down the Pacific coast by boat until they reached somewhere where travel inland was not blocked by ice. The Columbia River was probably the first such corridor they encountered.