I was wondering how much smaller was the Atlantic Ocean when each of these species were around: Australopithicus Afarensis, Homo Habilis, Homo Erectus, Neanderthal, and Cro-Magnon?

Well, the first step is to establish when they lived... here're some estimates:
Australopithecus ramidus - 5 to 4 million years BCE
Australopithecus afarensis - 4 to 2.7 million years BCE
Australopithecus africanus - 3.0 to 2.0 million years BCE
Australopithecus robustus - 2.2 to 1.0 million years BCE
Homo habilis - 2.2 to 1.6 million years BCE
Homo erectus - 2 to 0.4 million years BCE
Homo sapiens - 400,000 to 200,000 years BCE
Homo sapiens neandertalensis - 200,000 to 30,000 years BCE
Homo sapiens sapiens - 130,000 years BCE to present

I haven't been able to find any solid info on it, but continents apart drift at between about an inch and 4 inches a year... so, if my calculations are right, these are the ranges:

5 million years 79-316 miles
4 million years 63-253 miles
3 million years 47-189 miles
2 million years 32-126 miles
1 million years 16-63 miles
0.4 million years 6-25 miles
0.2 million years 3-13 miles
0.1 million years 2-6 miles

Thanks, methos. But wasn't the the Americas and Europe/Africa once together? I think you might've had your years swapped because shouldn't they be closer longer ago? Or is that 5 million years after they started drifting?

Your question was "how much smaller?"

Sorry I wasn't overly clear, but my answers were meant to be, "5 million years ago, the Atlantic was probably somewhere between 79 and 316 miles narrower than it is now (meaning the distance between Europe and North America was still 3,000+ miles), etc."

At the most, according to these calculations, In the 5 million or so years since Australopithecus ramidus, the distance between Europe and North America has change ~9% (since they are currently around 3,500 miles apart). At the least, the distance has changed by ~2%.

Based on 135 million years as an estimate of when N. Amer. and Eur. started to move apart, assuming a constant speed, we would calculate that they were only 129 miles (~4%) closer 5 million years ago. This is probably a more precise estimate.

Yes, the continents used to be closer together. The atlantic began to form 100-200 million years ago though, so the five million years of humanoid existance is short comparitively.

See here for some drawings of the earth at various stages.

[This message was edited by methos5000 on 04-07-03 at 11:37 AM.]

Thanks methos. That helps.