> > When I was doing a report on dreams a while
> > back, I read that that falling feeling is a
> > kind of memory from the VERY early human days,
> > when we lived in trees.
>
> I thought we'd always lived on the ground.
>
> And how do you have a memory of something that happened millions of years before your birth?

If it does come from that source, a better way to describe it would be "instinct" not "memory". You can't have a genuine memory of something that happened millions of years ago, but it seems possible that a species which evolved from tree-dwellers might still have some of the instincts that were useful back then. But Eric is right, you can't say "very early human days" if you're talking about tree-dwelling primates. There are an awful lot of ground-dwelling hominids in between the first humans and whichever of their ancestors left the trees. I don't know a lot about this, and what I do know is probably outdated, but I don't think you can start talking about "humans" before at *least* Homo erectus, but more likely the Cro-Magnons (first Homo sapiens).

When I was at university, the current state of knowledge was:
1) our original primate ancestor left the trees 15 million years ago,
2) three species of ground-dwelling hominids 3 million years ago (Australopithecus africanus, A. robustus, and Homo habilis),
3) Homo erectus evolved from H. habilis about 1.5 million years ago,
4) Neanderthals and Homo sapiens came along about 50,000 years ago, and finally
5) Homo sapiens became the dominant and eventually the only hominid species by about 11,000 years ago.

This is a rather pedantic way of saying that, yeah, "we" have always lived on the ground.

One thing I always find very interesting to think about, is what the world would have been like if one or more of the other branches of hominids had also survived. Going from what I know about them, I would have to consider Neanderthals "humans". What would it be like to live in a world with more than one intelligent talking species?

Of course, the cynical answer is "We'd kill off most of them and interbreed with the rest until there weren't any left", which is pretty much what scientists think already happened.