The Clash: The Ancient Genome And The Modern Diet
by Stephanie Allan
As humans, we often believe ourselves
exempt from the forces governing
other organisms, but this is
not true. Since hominids—humans
and our ancestors—emerged five to
seven million years ago, the majority
of our history has been spent following
a hunter-gatherer (HG) diet,
characterized by relatively large
quantities of lean game, wild plant
matter, and a little starch. One major
factor in human evolution has
been our unique ability to manipulate
our environment. While intelligence
may have increased over the
course of our evolutionary history,
the same perhaps cannot be said of
wisdom. In our unrelenting march
to “progress,” we have not stopped
to question whether the things we
can do are things that we should.
The introduction of agriculture
and animal husbandry approximately
10,000 years ago caused a
huge shift in diet, and further inventions
since the Industrial Era
have continued to alter our eating
habits even more drastically. While
our diet has changed rapidly, especially
over the last few centuries, our
genome is still adapted to the HG
diet of our ancestors. Some experts
believe this hasty departure from
our ancestral diet marks the beginning
of many so-called diseases of
civilization, which include obesity,
type-2 diabetes, and cardiovascular
disease. Could it be that our ability
to manipulate our existence to
fit our desires has ultimately led us
to create the weapons of our own
destruction?
Evolutionary theory states that
while no animal will actively develop
a harmful characteristic, there is
no guarantee that something once
useful will continue to be so as
circumstances change. This is the
premise of the discordance hypothesis
of disease, which focuses on the
dissonance between our genetic
heritage and our contemporary
lifestyle in disease development.
The discrepancy between the two
means that our bodies are unable
to properly process the novel substances
we ingest, in turn causing
the chronic degenerative diseases
that plague Western countries.
In order to determine the health
impacts of the modern Western
diet, it is beneficial to compare it
to our ancestral diet. While direct
comparison is not possible, we
can look to a number of sources to
give us insight. Our first source of
information comes from the fossil
record. The field of paleopathology
has gleaned huge amounts of
data about past health status from
fossil remains. Many excavation
sites throughout the world yield
pristine skeletal specimens prior
to the introduction of novel foods
like corn. However, once grains
replaced game and plant matter as
the basis of the diet, remains show
a marked increase in cavities, malnourishment,
rates of anemia, tuberculosis,
osteoarthritis, and other
degenerative diseases.
Another method to gauge the
impacts of the modern diet is to
examine the changing health status
of societies that have undergone an
evolutionary “fast-forward.” While
Europeans and their descendents
have lived in an agriculturallybased
society for several thousand
years, there are many societies that
have embraced the Western lifestyle
within only the last two centuries
or so. Examples include Australian
Aboriginals and North American
First Nations. Since colonization,
westernized aboriginal communities
have seen the incidence of diseases
sky-rocket to epidemic proportions,
to the point where 50-80
percent of adults are overweight or
obese and type-2 diabetes and cardiovascular
diseases are the norm
rather than the exception.
The previous two examples illustrate
how the modern diet seems
to have detrimentally affected our
health. However, it could be argued
that any number of factors in our
rapidly changing world could produce
these results. Let’s look to the
closest example we have of our ancestral
diet–remaining HG societies,
which are scattered worldwide.
While no discussion of diet and
health can ignore the impact of
exercise, this article will not delve
into the relationships. Suffice it to
say, there is a huge discrepancy in
the exercise habits of HG tribes
and Westerners. For example, it is
estimated that the !Kung San of the
Kalahari walk 10-15 km per day,
while American adults walk effectively
less than 1 km per day.
There is no universal HG diet;
rather, it changes regionally. There
are universal characteristics that
underlie all HG diets—they’re
comprised of minimally processed
foods with high nutrient density,
mainly wild plant matter and
game.
The HG diet is relatively high
in animal matter (45-65 percent
of daily energy), but meat is lean
and effectively devoid of saturated
fat. Diets are high in fibre, complex
carbohydrates, polyunsaturated
fats, and minerals, and are low in
saturated fat and sodium. Furthermore,
HG tribes eat little to none of
the dairy products, cereals, refined
sugars, vegetable oils, and alcohol
that make up over 70 percent of the
energy consumed by North Americans.
Since the discordance hypothesis
of disease was introduced,
many clinical studies have prescribed
diets similar to our ancestral
HG diet to alleviate or reverse
disease progression. Not surprisingly,
they have seen much success
in treating the target issues.
So what exactly have we done to
our food to create such evolutionary
discordance between our genome
and our diet? Many dietary
missteps are common knowledge—
we eat too much saturated fat and
salt, and not enough fibre—but we
typically brush them aside because
one extra slice of pizza can’t do that
much harm, right? Well, we couldn’t
be more wrong. The effects of our
modern diet on our ancient body
systems are so powerful that what
we eat is essentially killing us.
So what can we do about this
discordance? Our genome has remained
fairly constant over thousands
to millions of years, so it
seems unlikely that it will spontaneously
change to suit our eating
habits any time soon.
The other obvious answer is to
change our diet. But there is clearly
no way to revert back to our ancestral
diet, and even if we wanted to,
there simply is no longer enough
area on earth to sustain our planet
without commercial farming.
And so we come to a standstill.
Will biotechnology and the genetic
modification of our genome solve
the problems caused by the modern
diet? It sounds too science fictionish
to ever become a reality, but researchers
are currently examining
biotechnical methods to counter
genetic factors affecting obesity, so
why not change other diet-related
areas of our genome as well? Barring
this, it seems plausible that the
clash between our ancient genome
and modern diet will eventually
come to a head and we may share
a fate similar to that of the countless
organisms that failed to adapt
to changing conditions. The only
difference is that our ill fate will be
at our own hands.