Scientific American Feature
Article December 2002 issue
EVOLUTION
Food for Thought: Dietary change was a driving force in human evolution
by William R. Leonard
WILLIAM R. LEONARD is a professor of anthropology at Northwestern University. He was born in Jamestown, N.Y., and received his Ph.D. in biological anthropology at the University of Michigan at Ann Arbor in 1987. The author of more than 80 research articles on nutrition and energetics among contemporary and prehistoric populations, Leonard has studied indigenous agricultural groups in Ecuador, Bolivia and Peru and traditional herding populations in central and southern Siberia.
WL: We humans are strange primates.
True, and the
fiction they create disguised as "science" to support their
own personal cultural conditioning and superstitions, which they refuse
to examine logically, is even stranger.
WL: We walk on two legs, carry around enormous
brains and have colonized every corner of the globe.
We also have,
by the continuing misuse of those "enormous brains", brought
to extinction tens of thousands of other species of Life, polluted ourselves
and every corner of the planet, changed the weather on this planet, have
been at constant war with our own species throughout our history, and
are currently carrying on an unprecedented campaign of global ecocide.
WL: Anthropologists and biologists have
long sought to understand how our lineage came to differ so profoundly
from the primate norm in these ways, and over the years all manner of
hypotheses aimed at explaining each of these oddities have been put forth.
Simple: culture.
The other species are driven by instincts, thus can function only
in harmony with Nature, not destroy it and themselves through misuse of
intellect as humans do as a result of cultural conditioning. Some
of the primates, such as the chimp, are starting to develop culture as
shown by their limited flesh-eating.
WL: But a growing body of evidence indicates
that these miscellaneous quirks of humanity in fact have a common thread:
they are largely the result of natural selection acting to maximize dietary
quality and foraging efficiency.
Natural selection
made our species into the self- and omni-destructive plague that is currently
destroying our planet? This is, indeed, a perverted view of evolution.
"Quirks" of behavior are not the slightest bit related
to evolution, which occurs in the physical body, only. "Quirks"
of behavior exist only in the domain of culture/consciousness, which is
totally independent from, and different than, genetic processes.
WL: Changes in food availability over time,
it seems, strongly influenced our hominid ancestors. Thus, in an evolutionary
sense, we are very much what we ate.
Here, the false
and long-abandoned 18th Century Lamarckian
view of evolution, that personal behavior in one generation influences
the physical evolution of the species in the next, is invoked. If
were really "are what we ate", then the human species would
show some signs of "adapting" to a flesh-oriented diet; however,
we have developed no physiological or biochemical tools to do so successfully.
Further, the current epidemiology of degenerative diseases proves
otherwise, also.
WL: Accordingly, what we eat is yet another
way in which we differ from our primate kin.
Much to our
own detriment, as epidemiology shows.
WL: Contemporary human populations the
world over have diets richer in calories and nutrients than those of our
cousins, the great apes.
Thus, humans
are the only ape species to suffer rampant acute and "degenerative
diseases".
WL: Scientific interest in the evolution
of human nutritional requirements has a long history.
Yet, evolutionary
theory provides no known mechanism whereby any species can adapt to a
diet different that the one prescribed by its own biochemistry. The
"nutritional requirements" of the human ape has not changed
over time, and that is the reason cultural diets inevitably produce disease
profiles characteristic of their local chemistry.
WL: But relevant investigations started
gaining momentum after 1985, when S. Boyd Eaton and Melvin J. Konner of
Emory University published a seminal paper in the New England Journal
of Medicine entitled "Paleolithic Nutrition." They argued that the prevalence
in modern societies of many chronic diseases--obesity, hypertension, coronary
heart disease and diabetes, among them--is the consequence of a mismatch
between modern dietary patterns and the type of diet that our species
evolved to eat as prehistoric hunter-gatherers.
The glaring
error in the whole Paleolithic Diet mythology, conveniently and uniformly
overlooked by its proponents, is that there is no way our species could
have "adapted" to it, as opposed to our original tropical frugivorous
diet. The claimed successes of adopting a Paleo diet is an effect
due only to the fact that it is somewhat closer, chemically, to the original
than the modern, processed, low-fiber flesh/dairy/grain/junk food cultural
diets. Thus, reducing some of the modern dietary perversions
will produce some improvement; however, reducing them further by
adopting a frugivorous ape diet will obviously produce better results,
and this is born out in practice. The Paleo diet propagandists ignore
the fact that there is no mechanism espoused in modern evolutionary theory
that will allow any species to "adapt" to a diet radically different,
chemically, from its natural one. Note that we do not see any other
species changing its diet radically over time; only the human does this
due to culture and choosing to live in an environment not its natural
ecological niche.
WL: Since then, however, understanding
of the evolution of human nutritional needs has advanced considerably--
Is there any
evidence that any other species demonstrated any "evolution of nutritional
needs"? Do we see the diet of any other species changing over
time?
WL: ... thanks in large part to new comparative
analyses of traditionally living human populations and other primates--and
a more nuanced picture has emerged.
Major error:
"traditionally living human populations" also eat unnatural,
culturally-driven flesh-including diets that necessitate tools and fire.
This "Noble Savage" paradigm falsely assumes that such
tribes are eating the natural one for our species, and that is simply
not true if tools and fire are necessary to secure or consume any element
in that diet.
WL: We now know that humans have evolved
not to subsist on a single, Paleolithic diet but to be flexible eaters,
an insight that has important implications for the current debate over
what people today should eat in order to be healthy.
Nonsense: we
simply do not see any other species "evolving" to eat as "flexible
eaters" since animals eat as a function of their instincts which
obviously do not change over time or as a function of cultural whim (except
in those species "advanced" enough to be exhibiting cultural
behavior).
WL: To appreciate the role of diet in human
evolution, ...
We should look
at current evolutionary theory and discover that there are no mechanisms
elucidated by which any species' inherent biochemistry changes as a function
of its dietary input. Humans do not have this magical ability, either.
WL: Thus, by looking at the way animals
go about obtaining and then allocating food energy, we can better discern
how natural selection produces evolutionary change.
One does not
find this in contemporary evolutionary theory. This implies that
behavior influences evolution, the long-abandoned Lamarckian
theory.
WL: Chimps, gorillas and orangutans evolved
in and continue to occupy dense forests where only a mile or so of trekking
over the course of the day is all that is needed to find enough to eat.
Much of early hominid evolution, on the other hand, took place in more
open woodland and grassland, where sustenance is harder to come by.
So, the human
apparently abandoned its natural ecological niche, which resulted also
in its abandoning its natural diet.
WL: Indeed, modern human hunter-gatherers
living in these environments, who provide us with the best available model
of early human subsistence patterns, often travel six to eight miles daily
in search of food.
Here is another
fundamental error. Once our species abandoned its proper ecological
niche and the plants therein, and thus also abandoned its natural, biologically-correct
diet, any diets chosen in a different ecosystem can NOT be used as any
valid indication of human nutritional needs. That is, our inherent
digestive and assimilative biochemistry did NOT change to accommodate
any new, cultural diet; there is nothing in current evolutionary theory
that supports this even as a possibility, and certainly not as a fact.
By conveniently ignoring this fundamental fact, the Paleo Diet propagandists
blithely, dishonestly, and without the slightest bit of credible support,
claim it did.
WL: ... bipedalism can be viewed as one
of the first strategies in human nutritional evolution ...
Strategy implies
conscious decision; evolution occurs mechanically, without the slightest
bit of participation of the intellect of the individual or the evolving
gene pool.
WL: Across all primates, species
with bigger brains dine on richer foods, and humans are the extreme example
of this correlation, boasting the largest relative brain size and the
choicest diet [see "Diet and Primate Evolution," by Katharine Milton;
Scientific American, August 1993].
This allegedly
"choicest diet" of cultural humans has led directly to all the
currently-popular "degenerative diseases"
not seen in the wild.
See my
critique of Milton's
bizarre concepts and illogic.
Some real data, shown in this graph, however,
clearly indicate that largest primates eat NO "richer foods",
i.e. animal flesh, but conversely the smallest primates consume the most.
Note that the facts refute ML's propagandistic claims.
WL: According to recent analyses
by Loren Cordain of Colorado State University, contemporary hunter-gatherers
derive, on average, 40 to 60 percent of their dietary energy from animal
foods (meat, milk and other products).
Cultural diets,
hunter-gatherer or couch potato, are not the slightest bit useful for
developing an understanding of the optimally-healthy human diet. Bringing
in factual, but totally irrelevant, data to create the illusion of credibility
is a common, reprehensible tactic among propagandists.
WL: Modern chimps, in comparison,
obtain only 5 to 7 percent of their calories from these comestibles.
WL seems to also
accept the arithmetically-absurd concept of "%
of calories from xxx".
WL: Animal foods are far denser
in calories and nutrients than most plant foods.
True, and that
is a reason that eating them leads to obesity,
heart disease, cancer,
and toxin-producing putrefactive bacteria in the
colon.
WL: For example, 3.5 ounces
of meat provides upward of 200 kilocalories. But the same amount of fruit
provides only 50 to 100 kilocalories. And a comparable serving of foliage
yields just 10 to 20 kilocalories.
So what?? With
65% of Americans being overweight, obese, or morbidly
obese what is the point of "evaluating" the desirability
or appropriateness of "foods" based on calorie content alone?
Would he recommend coal or petroleum based on their calorie content
alone? There is an unstated and quite erroneous assumption in WL's
irrational pro-meat propaganda, and that is that all ingested dietary
calories are efficiently and totally converted to usable calories, and
that is simply not true. The body muscles and brain uses glucose,
blood sugar, as a source of energy, and it is a lot easier to convert
fruit sugars, and less easy to convert starches, to glucose than animal
protein or fat.
Nuts have a calorie density comparable to
meat, and there is NO cholesterol, cooking-induced carcinogens, artery-clogging
animal fats, denatured protein, farm-chemical
residues, bacterial contamination, antibiotics,
or other hazards inherent in meat consumption.
WL: It stands to reason, then,
that for early Homo, acquiring more gray matter meant seeking out more
of the energy-dense fare.
No, there is
no "reason" here; this "meat-eating caused brain growth
in humans" theory is commonly touted in Paleo propaganda, yet strangely,
obligate carnivores did NOT produce large brains as a result of their
only-flesh-consumption, and conversely the large brains of the elephant
and gorilla do quite well on plant-based diets. Several misconceptions
about brain size are discussed here.
WL: Fossils, too, indicate that improvements
to dietary quality accompanied evolutionary brain growth.
There is no way
to "improve dietary quality", since the proper/optimum diet
for any species is fixed at the genetic level and manifested
by each individual species' inherent physiology, biochemistry, and instincts.
There is no way to "improve" on the original design by
cultural diets, and the profusion of cultural diet-caused degenerative
diseases is proof of that. I am always amused by such pseudoscientific
claims regarding the great wonders conferred to our species by flesh-eating,
when the proponents of such claims can not explain just why the human
did NOT evolve the sharp, pointy tools seen among all natural flesh-eaters,
and especially why we did NOT evolve instincts to capture, kill, and eat
flesh raw. In fact, there is a strong anti-instinct to do so, and
no proponent of these nonsensical theories will test their beliefs by
killing and eating raw any small animal, using only their natural equipment.
WL: (This is not to say that australopithecines
never ate meat. They almost certainly did on occasion, just as chimps
do today.)
Strangely, people
who bring this trivial fact up never indicate that this is strictly a
cultural practice among chimps, and certainly
not a nutritional imperative. Shouldn't anthro-apologists
be able to distinguish between culture and Nature?
WL: As to what prompted Homo's initial
shift toward the higher-quality diet necessary for brain growth
There is no evidence
that any "higher-quality" diet exists; the proper diet for any
species is dictated at the genetic level. Similarly, there is no
evidence that different diets are necessary for small or large brains.
WL: The continued desiccation of the African
landscape limited the amount and variety of edible plant foods available
to hominids.
True, but irrelevant
to any discussion of the natural/optimum diet for our species as these
groups had left their proper ecological niche and the plant communities
therein.
WL: As it turns out, the spread of grasslands
also led to an increase in the relative abundance of grazing mammals such
as antelope and gazelle, creating opportunities for hominids capable of
exploiting them. H. erectus did just that, developing the first hunting-and-gathering
economy in which game animals became a significant part of the diet and
resources were shared among members of the foraging groups. Signs of this
behavioral revolution are visible in the archaeological record, which
shows an increase in animal bones at hominid sites during this period,
along with evidence that the beasts were butchered using stone tools.
True, but irrelevant,
since the use of tools/fire is absolutely and unquestioningly not necessary
with our biologically-corrent diet; conversely, their use proves that
the items for which they are necessary are NOT part of our natural diet.
It is insightful that anthro-apologists conveniently obfuscate or
ignore the profound differences between Nature and culture to support
their hollow theories. Will the evidence of pesticide pollution
in our corpses some 10,000 years from now convince those future anthro-apologists
that we somehow "adapted" to pesticides?
WL: ... the addition of modest amounts
of animal foods to the menu ... would have significantly increased the
quality and stability of hominid diets.
No evidence
is presented that links animal foods and "quality" of diets.
In fact, there is none; however, there is abundant and convincing
data that all the currently-popular "degenerative
diseases" are linked with the consumption of "animal foods".
This false link is simply assumed as a result of WL's cultural programming
and superstition; clearly, he has not any personal experience with plant-based
diets, or such foolishness would not be presented as fact. Insightfully,
people who tout human flesh-oriented diets, or disparage human plant-based
diets, generally have not had any personal experience
with the latter.
WL: The impetus behind this newfound wanderlust
again appears to be food. What an animal eats dictates to a large extent
how much territory it needs to survive. Carnivorous animals generally
require far bigger home ranges than do herbivores of comparable size because
they have fewer total calories available to them per unit area.
But, wait. Weren't
we told that a flesh-oriented diet was "better" since it was
more calorie-dense and thus necessitated less locomotion? Carnivores
do not have "home ranges"; they follow herbivore herds, or hang
out at watering holes, and have an incredibly-populous food sources available
at all times.
WL: Large-bodied and increasingly dependent
on animal foods, H. erectus most likely needed much more turf than the
smaller, more vegetarian australopithecines did. Using data on contemporary
primates and human hunter-gatherers as a guide, ... I have estimated that
the larger body size of H. erectus, combined with a moderate increase
in meat consumption, would have necessitated an eightfold to 10-fold increase
in home range size compared with that of the late australopithecines.
Weren't we told
above that a "better", more calorie-dense diet necessitated
LESS locomotion to obtain it?
WL: -- enough, in fact, to account for
the abrupt expansion of the species out of Africa. Exactly how far beyond
the continent that shift would have taken H. erectus remains unclear,
but migrating animal herds may have helped lead it to these distant lands.
And, moving out
of our natural ecological niche also was responsible for the "addiction"
our species developed to tools and fire, with the logical diminution of
health resulting from using such.
WL: As humans moved into more northern
latitudes, they encountered new dietary challenges. The Neandertals, who
lived during the last ice ages of Europe, were among the first humans
to inhabit arctic environments, and they almost certainly would have needed
ample calories to endure under those circumstances. Hints at what their
energy requirements might have been come from data on traditional human
populations that live in northern settings today. The Siberian reindeer-herding
populations known as the Evenki, which I have studied with Peter Katzmarzyk
of Queen's University in Ontario and Victoria A. Galloway of the University
of Toronto, and the Inuit (Eskimo) populations of the Canadian Arctic
have resting metabolic rates that are about 15 percent higher than those
of people of similar size living in temperate environments. The energetically
expensive activities associated with living in a northern climate ratchet
their caloric cost of living up further still. Indeed, whereas a 160-pound
American male with a typical urban way of life requires about 2,600 kilocalories
a day, a diminutive, 125-pound Evenki man needs more than 3,000 kilocalories
a day to sustain himself. Using these modern northern populations as benchmarks,
Mark Sorensen of Northwestern University and I have estimated that Neandertals
most likely would have required as many as 4,000 kilocalories a day to
survive. That they were able to meet these demands for as long as they
did speaks to their skills as foragers.
Interesting
as these comments are, they completely ignore the negative health consequences
of living is such unnatural environments and consuming the unnatural diets;
that is, why do these types of "analysis" always ignore the
poor health and shortened life spans of these tribes?
Modern Quandaries
WL: Just as pressures to improve dietary
quality influenced early human evolution, so, too, have these factors
played a crucial role in the more recent increases in population size.
Where do we
see these supposed "pressures to improve dietary quality" elsewhere
in Nature? Nowhere. They did not exist.
WL: Innovations such as cooking, agriculture
and even aspects of modern food technology can all be considered tactics
for boosting the quality of the human diet.
There is no
rational argument that suggests that cooking and/or modern food technology
"boosts" the "quality of the human diet"; in fact,
the opposite is true.
WL: Cooking, for one, augmented the energy
available in wild plant foods.
The cooking
of starchy plants, such as roots and tubers, increases the availability
of starch for digestion because the cell walls are broken, thus cell contents
are more readily available to digestive enzymes. However, the creation
of carcinogens, mutagens, teratogens, Maillard
reaction chemicals, cross-linked protein-sugar complexes, various toxic
and foreign species of chemicals, and the reduction of the nutritional
efficacy of many nutrients by cooking are all conveniently ignored.
WL: With the advent of agriculture, humans
began to manipulate marginal plant species to increase their productivity,
digestibility and nutritional content-- essentially making plants more
like animal foods. This kind of tinkering continues today, with genetic
modification of crop species to make "better" fruits, vegetables and grains.
Similarly, the development of liquid nutritional supplements and meal
replacement bars is a continuation of the trend that our ancient ancestors
started: gaining as much nutritional return from our food in as little
volume and with as little physical effort as possible.
Conveniently,
the ongoing reduction in nutritional quality of commercial products over
time as a result of this continuing "progress" and the coming
horrors related to genetically-modified organisms being released into
the wild are ignored.
WL: Overall, that strategy has evidently
worked: humans are here today and in record numbers to boot.
When did quantity
relate to quality? The health of people who are victims to this
"tinkering" is rapidly decreasing, as seen in the ever-increasing
disease statistics.
WL: But perhaps the strongest testament
to the importance of energy- and nutrient-rich foods in human evolution
lies in the observation that so many health concerns facing societies
around the globe stem from deviations from the energy dynamic that our
ancestors established.
Here, the false
concept that our ancestors' misguided nutritional perversities somehow
affected our genes in a way such as to require our continuing their mistakes
is propagated again.
WL: For children in rural populations of
the developing world, low-quality diets lead to poor physical growth and
high rates of mortality during early life. In these cases, the foods fed
to youngsters during and after weaning are often not sufficiently dense
in energy and nutrients to meet the high nutritional needs associated
with this period of rapid growth and development. Although these children
are typically similar in length and weight to their U.S. counterparts
at birth, they are much shorter and lighter by the age of three, often
resembling the smallest 2 to 3 percent of American children of the same
age and sex.
Could the growth
hormones, both natural and artificial, in animal products be responsible
for this excessive growth? When did bigger mean better? Especially
with the global epidemic of obesity rapidly following the introduction
of "modern civilized foods"?
WL: In the industrial world, we are facing
the opposite problem: rates of childhood and adult obesity are rising
because the energy-rich foods we crave--notably those packed with fat
and sugar--...
Hmm, animal
and junk "foods" ; exactly what was touted as beneficial "tinkering".
WL: Obesity has also appeared in parts
of the developing world where it was virtually unknown less than a generation
ago.
As tradition
diets, somewhat closer to our nutritional needs, are abandoned in favor
of "tinkered foods", including more animal foods.
WL: We are victims of our own evolutionary
success, ...
What an incredibly
stupid thing to say. It is "evolution's" fault for the
current state of degenerate health existing only in the human species.
WL: The magnitude of this imbalance becomes
clear when we look at traditionally living human populations. Studies
of the Evenki reindeer herders that I have conducted in collaboration
with Michael Crawford of the University of Kansas and Ludmila Osipova
of the Russian Academy of Sciences in Novosibirsk indicate that the Evenki
derive almost half their daily calories from meat, more than 2.5 times
the amount consumed by the average American. Yet when we compare Evenki
men with their U.S. peers, they are 20 percent leaner and have cholesterol
levels that are 30 percent lower.
The dietary
practices of people living so far from our natural ecological niche has
no relevance to our optimally-healthy diet. What is the life span
and health profile of these people? This important data is always
ignored in "the noble savage" paradigm.
WL: These differences partly reflect the
compositions of the diets. Although the Evenki diet is high in meat, it
is relatively low in fat (about 20 percent of their dietary energy comes
from fat, compared with 35 percent in the average U.S. diet), because
free-ranging animals such as reindeer have less body fat than cattle and
other feedlot animals do. The composition of the fat is also different
in free-ranging animals, tending to be lower in saturated fats and higher
in the polyunsaturated fatty acids that protect against heart disease.
More important, however, the Evenki way of life necessitates a much higher
level of energy expenditure.
So, he admits that
such "apple and orange" comparisons are useless?
Again, we see that anthro-apologists have abandoned real science, facts, and logic in their fanciful creative writing efforts.