Were Early Humans Vegetarian?
By: Sally Grande And Stephen Leckie
Ironically, our greatest achievement as a species may be applying our enlarged
brain and our technology to recreating the diet we instinctively ate a million years
Imagine the primordial jungle. Imagine many kinds of primates, including
anthropoids (chimps, gorillas and early humans) foraging for fruits and
protein-rich leaves in the canopy of the arboreal forest.
This story begins more than 55 million years ago but it has been the life-long
study of Dr. Katherine Milton, professor of anthropology at the University of
Her quest for links between diet and evolution is shared by David Popovich, a
doctoral student in nutritional sciences at the University of Toronto, who also
sees a connection between diet and human development of vision, depth
perception, memory, speech, dexterity and social behaviour.
We have been given the impression that our early ancestors were closer to
carnivores than they were to plant eating animals. The degree of meat in the
early hominid diet is a matter of controversy and the more conservative view
sees evidence for including small amounts of meat in the ancestral diet through
opportunistic foraging and scavenging.
The ancestors in question lived long before any modern human predecessors.
The National Geographic Society's recent report on Neanderthal life in glaciated
Europe, for example, cites evidence of cannibalism and reliance on hunting for
However, these primate cousins were relatively recent in hominid history. Our
original ancestors predate them by eons, long before the last great ice age. The
early hominids were much more similar to modern day chimpanzees and gorillas.
Most of us think of a chimp's life as being fairly carefree. Dr. Milton was
surprised when she was observing a troupe of chimps and noticed that, instead
of sitting around in the tree branches and eating what was nearby, they hurriedly
sought out specific foods, rejecting a number of delicious looking leaves in order
to move on.
When they found an acceptable specimen, they did not gorge themselves.
Instead, they seemed driven to obtain a mixture of fruits and leaves from a variety
of plant species. On the spot, Dr. Milton decided to devote her career to studying
how these animals met their nutritional needs.
Chimps in the wild today face many challenges to obtaining a sufficient variety of
plant material - similar challenges were likely faced by our distant ancestors.
For starters, many plants have developed outer coatings to discourage hungry
herbivores. These outer layers contain chemical compounds that taste terrible
and sometimes are lethal.
In addition, the fibrous content of plants, which we call "fibre" or "roughage,"
resists breakdown by mammalian digestive enzymes. Excessive intake of fibre
is troublesome because when fibre goes undigested, it provides no energy for
The trick is to do a better job of digesting the fibre. At the University of Toronto,
David Popovich has been studying the micro-nutrient content of the wild
vegetation consumed by gorillas.
He has found that much of the energy and nutrient value that gorillas are able to
derive from such a diet comes from colonic fermentation. Their studies on
human subjects have shown that humans may also be able to rely on colonic
Thus, a diet consisting of substantial quantities of fruits, vegetables and nuts -
no pasta or starches - will provide adequate protein, B-12 and amino acids (the
building blocks of protein).
Gorillas and chimpanzees have little trouble digesting cellulose thanks to the
presence of the ciliate Troglodytella in their intestines. However, chimps and
gorillas in captivity begin to lose their Troglodytella when they are fed cooked
food. Thus, it is reasonable to assume that humans lost their intestinal cilia when
they started cooking with fire.
While the amount of meat consumed by our distant ancestors is still debated,
there is consensus that the Pleistocene diet consisted overwhelmingly of
Another concern with such a diet is finding time to forage. Primates cannot
concentrate on just a few plant sources because, even if the fibre could be
well-digested, many plant foods are low in one or more of the required nutrients,
such as vitamins or amino acids.
Fruits tend to be rich in easily digested forms of carbohydrate and relatively low
in fibre, and provide little protein. Given that primates in the arboreal canopy do
not cultivate protein-rich beans and vegetables, they rely heavily on efficient
access to a wide variety of preferred fruits and leaves to achieve adequate
Developing a better memory for the exact location of favored trees, the shortest
routes between them and a timetable for when they would likely be fruit-bearing
would definitely favor survival.
A larger brain would no doubt support these activities as well as group
communication. Today, spider monkeys comb the forest for fruit by dividing into
small, changeable groups. Their expanded mental capacity helps them
recognize members of their own social unit and learn the meanings of different
The inherent complexities of the plant food niche could have been a factor in
increasing the longevity of primates. Neither apes nor humans can rely on their
relatively poor senses of taste and smell to detect toxicity, so they require several
years of adolescence to learn which foods are safe and nutritious. This may be
why humans are one of the longest living animals on earth.
Dr. Milton claims that the crafty Homo sapiens were better equipped to solve the
dietary problems wrought by changing environmental conditions. Expansion of
brain power in combination with growth in body size and reduction in the jaw
and teeth, are evidence of achievement of a high quality diet.
Without the high quality diet, the increased body size simply produces a slow
moving, fairly sedentary and unsociable ape, like present-day orangutans and
Dental patterns among fossils of hominids support evidence of a high quality,
plant-based diet. The decreased mass of the jaw and teeth signify that either our
ancestors were eating less fibrous; easier-to-chew foods or they were
processing them to remove material that would be hard to digest.
Some researchers have proposed that modification in dental structures resulted
partly from specialization in hunting and scavenging. However, electron
microscope examination of bones collected from early hominid sites reveals that
our ancestors most likely scavenged bones that were already ravaged by
While the amount of meat consumed by our distant ancestors is still hotly
debated, there is consensus that the Pleistocene diet consisted overwhelmingly
of vegetable material.
While chimpanzees are known to kill, this behavior is not necessarily dietary but
ritualistic and their diet is at least 94% plants and fruits.
Wild chimps take in 100 grams of fibre each day, much more than the 10 grams or
less that the average North American ingests today. Dr. Milton's studies have
shown that the chimpanzee gut is strikingly similar to the human gut in the
efficiency with which it processes fibre.
According to Dr. Milton, our digestive tract does not seem to be greatly modified
from that of the common ancestor of apes and humans, which was undoubtedly
a predominately herbivorous animal.
While there is no authoritative recommendation for the daily intake of fibre, the
small amount ingested daily by most Canadians is far less than we need to
According to David Popovich, captive gorillas are dying in zoos of the same
arterial sclerosis afflicting human cardiac patients because the zoos are unaware
of the gorillas' reliance on fibre.
Dr. David Jenkins, known as the father of the "fibre movement" in Canada and
Director of the Clinical Risk Factor Modification Center at St. Michael's Hospital,
continues to make a strong case for vegetarianism as the optimum human diet.
By: Sally Grande and Stephen Leckie