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Research into the diet of ancient hunter-gatherers shows that
our diet of cereals and grain-fed meat
is not what we have evolved to eat.
A group of scientists, from dozens of disciplines, has lately
started to put together a model of the diet "designed"
by evolution for the human body. When the dust settles on
their investigations, most of today's arguments about human
nutrition might have been laid to rest.
The new field of "evolutionary diet" is (literally)
unearthing the dietary patterns of our paleolithic ancestors.
The paleolithic was humanity's final formative period, stretching
for hundreds of thousands of years, and culminating about
10,000 years ago.
After this time, cereal crops were domesticated, and humankind
began to eat grains. This was a dramatic departure
- until that moment we had evolved for at least 2 million
years as hunter-gatherers and scavengers.
A scientist who has researched paleolithic diet for many
years, Professor Loren Cordain of Colorado State University,
says that after humans started domesticating crops, low levels
of vitamins, minerals and amino acids led to "poor
general health" - and a drop in human stature
of 10 to 15 centimetres.
Cordain is perhaps the world authority on evolutionary diet,
or "paleodiet". Paleodiet information is derived,
he says, from the fossils of many human individuals, of up
to 2.4 million years old.
He says that the change to an agricultural diet led to
- an increase in infant mortality
- a reduction in life span
- an increased incidence of infectious
diseases
- an increase in iron deficiency
anemia
- an increased incidence of bone
mineral disorders
- an increase in the number of
dental caries
Another paleo-scientist, Professor Arthur de Vany of California
State University, puts it more pointedly: "It is easy
to tell from the skeletons of our ancestors whether they were
agriculturists or hunter-gatherers. The agriculturists have
bad teeth, bone lesions, small and underdeveloped skeletons,
and small craniums, compared to hunter-gatherers."
Naturally these findings have prompted closer study of what
we were eating before the advent of agriculture - when there
were lower levels of disease.
It has posed the question:
which foods has evolution equipped
homo sapiens to thrive on?
Work is not complete on this, but some broad facts are emerging.
First and foremost is that humans, and pre-humans, have eaten
meat continuously for 2 to 3 million years. Meat has, for
the most part, been the largest single component of the human
diet. Our ancestors were likely more interested in animals'
organs - tongue, heart, liver, kidney - than the flesh, the
former having greater micronutrients and "good"
fats.
Paleolithic humans' carbohydrate came chiefly from roots,
tubers, leaves and wild fruits. But modern humans can't take
this as license to eat large amounts of fruit. "Ancestral"
fruit was vastly less sugary than today's selectively bred
varieties, and far more fibrous. Replicating it from your
greengrocer would necessitate concentrating on vegetables
and "low glycemic index" (less sugary) fruit.
Cordain believes today's surviving hunter-gatherers provide
a fair guide to the ratio of plant-to-animal food in the paleolithic
diet: his surveys reveal that these people eat up to 65 per
cent of their calories in animal food, and 35 per cent in
plant food.
The present animal-plant ratio in the US diet is 38:62 -
a near-reversal of the evolutionary pattern. Cordain cites
these macronutrient ratios, in calories:
Paleolithic: fat-22%
protein-37% carbohydrate-41%
US today: fat-34%
protein-15.5% carbohydrate-49%
So we now eat more than 50 per cent more fat than we evolved
on - and much of it "new"
fats, notably those in oils and dairy.
But the larger difference is in
our protein consumption - which is less than half what it
was.
But today's meat-eater should be careful in emulating paleolithic
protein intakes, too. Ancestral game was free-ranging,
and highly active. Today's slaughter animals are often fed
a diet high in cereals - which does to animals what it does
to humans: kicks up insulin, which tells the body to store
fat. Paleo-scientists counsel eating white or lean meat.
The ancestral record does not support the SAD (standard Australian
diet) - but neither does it add credence to diets seen as
"natural" by vegetarians, fruitarians, natural hygienists,
macrobiotic followers and their countless splinter groups.
There have been striking individual health improvements in
those applying paleodiet principles - including remissions
from chronic fatigue, autism, diabetes and MS. But these are
one-offs. There have, as yet, been no clinical trials of the
paleolithic diet - insofar as there is even consensus on what
it is. And, of course, the diet of our paleolithic ancestors
was inseparable from their whole lifestyle - the most crucial
aspect of which was exercise.
SMH.COM.AU
February 20, 2001
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