> I disagree.  It matters a great deal whether one
> draws the line
> at 40,000 or 10,000 years ago.  The former date is
> not really
> within hailing distance of agriculture or even
> pastoralism, as
> far as we can tell.  These were hunter-gatherers
> who, for some
> reason, suddenly became more sophisticated.

Possible explanations: Improved hunting techniques
using better implements and/or dogs allowed larger
game to be hunted. Increased use of fire which allowed
for better drying/storage techniques (and made
previously inedible foods edible). Climate changes
which improved hunting & gathering prospects.

Whatever the true explanation, it emphasizes the
exponential or "plateau" hypotheses of learning and
development of human consciousness. The first great
leap may have been 40,000 years ago. The next great
leap may have been the advent of agriculture and
husbandry 10,000 years ago, which allowed for the
creation of a "ruling class". You might argue the next
was the development of the printing press (I like that
one). And then human knowledge began to build at a
rapidly increasing pace to the point where we are
today. So, it could be argued that each of those
"events" had to occur before the width and breadth of
human knowledge could develop.

If it were truly a linear process, then why would it
take 10,000+ years for us to create a steam engine
when the skills/tools/materials have existed since the
advent of metallurgy?