Just want to say everyone, that after a long silence on the Palaeolithic
Diet symposium, what a great discussion this is.
Have decided that I am going to reply to lots of points raised by
different people in two emails, separated by subject, as otherwise we are
getting longer and longer messages with things copied in. I shall reply to
Ed Thompson's more specific email re his and my views in another, so
everyone can skip that if too bored or not enough time!

So, this posting concerns obesity.
Ed Thompson suggests that I think the current increase in obesity is due
to lack of willpower, whereas he has his suspicions of the conspiring food
industry. In a way I do think it related to willpower, but totally
unavoidable as it is an age old drive to eat more, as I go with the
'thrify gene' theory that humans throughout all evolution have struggled
against starvation, and therefore we have been genetically selected to be
on the plump side - gain weight easily in times of plenty,
so there is a reserve in times of hardship. For a great, if v personal
view of recent selection pressures such as documented famines, see:
Prentice, A. M. (2001). Fires of life: the struggles of an ancient
metabolism. Nutrition Bulletin 26: 13-27. A thought-provoking read.

I don't think we can blame the food industry, because all they are doing
is capitalising on a natural urge. We are programmed to prefer energy
dense foods, and this programming came about long before the food industry
happened. Look at the goddess figurines from Neolithic Catal Huyuk in
Turkey (6000BC) - they are hugely fat. Fat has been recognised and
worshipped as desirable for a long time in human culture and society,
until very recently when all of a sudden there was no shortage of foods
to balance out our desire to eat.
This desire for energy-dense foods is also why people will never be able
to eat as much as they like and be as thin as they like, despite what Bob
Avery says. Because what he overlooked in his comment that we would be
fine if we all ate only raw veggies, is that when people want to eat as
much as they like, they want to eat as much as they like OF FOODS THAT
THEY LIKE. I would venture that most people would think that eating only
raw veggies isn't that much more palatable than cutting back.

Thinking about human weight and whether we are the only species that
struggle.
Barry Groves says that 'all animals in their natural habitat are a normal
weight.' That point is one that most animal researchers would debate. Some
can often be severely underweight. The mechanism for controlling animal
weight in the natural habitat is not simply natural satiety, although that
will play a part. There can be an oscillation in weight of an individual,
as Andrew Millard pointed out in the case of an overweight lion that
cannot catch its food, so starves until it is thin enough to be fast
enough to catch it. Or there can be changes in the population size and
structure resulting in the most number of (just) reproducing individuals,
who are not necessarily in prime individual health. The latter point has
been amply demonstrated in the red deer on Rum: Tim Clutton-Brock et al.'s
work that a season of plenty leads to fatter deer in the very short term
but then greater reproductive success which will use up all the reserves.
A similar thing has been observed in feral donkeys in Australia, where
after culling of a population to provide more grazing per individual and
improve individual fitness, the population rebounded in size very quickly,
growing at 20% a year, and with far greater survival of neonates, to get
back to the original density. Both studies are detailed in a v good book:
White, T. R. C. (1993). The inadequate environment. Nitrogen and the
abundance of animals. Berlin, Springer Verlag.

On the flip-side, we are not the only animals that will be obese if given
the chance. Robert Sapolsky's famous study of a olive baboon troop in the
Masai Mara, whom he wrote about as 'junk food monkeys', completely
abandoned their usual diet when they discovered that they could feast to
their hearts' content on garbage from the national park buildings. Despite
that they matured earlier and had a wonderful time with endlessly
available food, they also became obese, cholesterol (LDL) rose, and they
all finally got a nasty dose of bovine TB. I know that one can hold up
hands in horror and say humans were responsible for the waste, but the
baboons CHOSE to eat this food, because it was an easy life. We humans do
much the same.

Next mail: carnivore or omnivore??

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Dr Tamsin O'Connell
Research Laboratory for Archaeology
University of Oxford
6 Keble Road, Oxford, OX1 3QJ, UK
tel:01865-283641
fax:01865-273932
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