Thanks, Hilary,

This is a very uncertain area, especially as we have to rely on secondary
evidence, not primary evidence.  And even the secondary evidence does not
indicate an unambiguous unidirectional progression.

However, the following appears to be a reasonable broad-brush picture of
what happened:

6-4 mya the climate cooled and became less stable and forests contracted.
Chimps and pre-humans split, with chimps remaining arboreal and pre-humans,
while still eating fruit, nuts and other tree-borne foods, also exploited
food on the ground (tubers, seeds, vegetables).  The retreating forests and
the encroaching savannas gave the pre-humans an ecological niche.

4-2.5 mya the cooling conti
nued, forests receded and plains increased and
there were more grazing animals for food.  At about this time, three things
happened and we can't say for sure which came first and, therefore, which
way the causality - if any - ran.  These three things were (1) the
development of stone tools which could be used used to butcher animals and
break their bones to get to the marrow and (2) a switch from primarily
plant foods to primarily flesh foods and (3) a rapid increase in brain size
which is a key marker distinguishing the Homos from the
Australopithicenes.  Further refinements of stone tool making appear to
correlate with increases in skull capacity which, palaeoanthropologists
assume, was also correlated with an increase in mental powers - the ability
to co-operate in hunting, food sharing etc.

Cooking, by the way, appears to have become common only 1 mya.

So, yes, berries and other food
s originating in the forests are important,
but it is the tubers I would like to know a little more about.  Tubers
cover a wide variety of foods.  Potatoes are a tuber, but they were not in
Africa.  I worked in the Highlands of Papua New Guinea in the 1970s where
kaukau - their version of sweet potato - was the staple.  Here in Australia
I have, as a child, eaten straight from the ground the tiny tubers of the
onion grass.  These are spherical vegetables about half the diameter of
your little fingernail.

So, with these three sorts of tubers (and the first two requiring cooking)
I'm interested to know about the sorts of tubers that existed on the
African savanna 6 mya and which probably became a staple for pre-humans.
We must have some biological adaptation to these tubers left over from that
period and I'd like to see what these tubers were and play around with them
in my diet.

Any further help wou
ld be much appreciated.

Keith

-----------------------------------------------------------------
To unsubscribe from the list send an email to [log in to unmask] with the words SIGNOFF EVOLUTIONARY-FITNESS in the _body_ of the email.

To get a copy of the old archives or the FAQ, look in the EvFit folder at http://briefcase.yahoo.com/dryeraser