In order to learn more about carbohydrates in human evolution I sent a mail
to Dr. Daniel Livingstone, a highly respected paleoecologist and
limnologist who holds the James B. Duke Professorship of Zoology and
Geology at Duke University, where he has been since 1956.  He has worked in
Nova Scotia, arctic Alaska, and especially tropical Africa on lakes and
their history. He is best known as the designer of the Livingstone sampler
for lake sediments, and for having been tasted and rejected by a large Nile
crocodile. This is my question ....

>It has been put forward e.g. by Brand Miller (Brand Miller JC, Colagiuri S.
>The carnivore connection: dietary carbohydrate in the evolution of NIDDM.
>Diabetologia 1994; 37: 1280-6) that human diet was low in carbohydrate from
>the time of H. habilis up to sapiens leaving Africa, allegedly because dry
>climates during the Ice Ages would result in grasslands being the main
>edible plants instead of roots and fruits.
>
>Please give me your opinion on this issue which is important to
>evolutionary medicine in order to know wether there is evidence of an
>optimal balance of macronutrients for humans.

... and his answer:

The question may be of significance, but I doubt that my opinion on it is
worth much.

However, for what it is worth, I wouldn't bet much on this idea.  It rests
on such a train of untested ideas that the final conclusion doesn't have
much weight.

First, very little is known about the environment of early paleolithic
people.  We know something from pollen analysis about the nature of tropical
African vegetation during the last part of the last ice age and the time
since then.  We get a few glimpses of what things were like during earlier
periods from studies of the isotopic composition of old soils, marine cores,
plant fossils, mainly leaves, buried under volcanic ash, and an occasional
pollen analysis of the sediment from paleoanthropological sites.

The picture that emerges is one of a complex mosaic of vegetation types.
During the last ice age, and presumably earlier ones as well, although this
is not a well-tested presumption, the vegetation was richer in grasses and
poorer in trees than it has been during post-glacial time.  It is not easy
to place most archaeological sites accurately in that shifting vegetational
context, but Desmond Clark, the dean of African prehistorians, believes that
until Sangoan time, which may be 100,000-200,000 years ago or so, when a
culture developed that was intermediate between the late Acheulian and
Middle Stone Age, people were not adapted to life in a forest.  This is an
interesting idea, and well worth serious stratigraphic testing.  I have
tried but failed to give it a usefully rigorous test.

It is likely that people from early paleolithic time onward lived in a more
or less open vegetation.  Paleolithic sites seem to cluster around water,
and it is likely that our ancestors, like ourselves, were obliged to drink
water, and not having containers larger than ostrich shells, could not carry
it very far.  There is always a possibility that they had skin or gourd
containers, but sewing up skins would probably require stone tools such as
burins, which don't show up until much later in the record.  It is always
possible that they could get by without drinking water, as gorillas and some
antelopes do, but the distribution of sites argues against this.

In the African vegetation matrix, the local vegetation close to permanent
water tends to be richer in trees than the vegetation farther away.  I don't
mean to argue for gallery forest around every cluster of Olduwan tools, but
only to suggest that it is not likely that early Paleolithic people spent
their lives far away from trees.

From watching baboons, and from keeping a Canadian countryman's eye on the
resources that might be used for food in an emergency, I don't think that
even in a grassland early Paleolithic people would find it difficult to
consume carbohydrates.  I would expect them to depend heavily on grass
seeds, and from the time they had digging sticks, on underground storage
organs of vascular plants.  I don't eat them in Africa, because some are
very poisonous and I don't know which are safe, but I have no reason to
believe that our early Paleolithic ancestors were so ignorant.

As for what those people actually ate, that is still an open question, so
far as I know.  There has been some isotopic analysis of their bones, but I
have not followed that closely enough even to tell if it suggests membership
in a food chain based on C-3 or C-4 plants.  In this state of affairs, there
is a place for speculative papers suggesting that they did not consume
appreciable quantities of carbohydrates, but that speculation doesn't seem
to me very solid, and I wouldn't modify my diet, nor advise you to modify
your dietary advice, in accord with it.

You really need to get in touch with paleoanthropologists about this.  The
people who work with Lower Paleolithic cultures are excellent natural
historians, they read the papers we publish on the paleoecology of Africa,
and they are in a better position to have currently valid opinions than I
am.  Try Dr. Robert J.  Blumenschine in the Anthropology Department of
Rutgers University, Rutgers, New Jersey, USA ([log in to unmask]).

Our African heritage affects our health in other ways.  Our peculiar
fluoride requirement looks like a legacy of a prehistory spent where waters
are fluoride rich.  Possibly something similar is behind our lithium
requirement.

People tend to develop semi-religious feelings about questions of this sort.
When I was a boy, much influenced by the writings of Viljhalmur Steffansson,
I believed that we were all natural carnivores, because Innuit were heavy
meat-eaters and free of dental caries.  I was dragged kicking and screaming
to acceptance of the idea, based on studies of Kalihari Bushmen and the
great apes, that our early ancestors were probably omnivores, with a heavy
component of plant material in their diets.  Maybe I burn with the zeal of
the newly converted, and you should be wary of my opinion for that reason.

I think, though, that it is no such faith, but rather a cold assessment of
what little we know about the history of African vegetation that makes me
skeptical of the idea that early Paleolithic people lived in an environment
so poor in potential carbohydrate foods that they had to eat other things.
That is probably the only part of my opinion that you care about, since you
will know more than I do about the other stuff.

I hope that this helps.

Dan Livingstone

[end of included e-mail]

I have posted the same question to Dr Blumenschine.

Staffan