Why is it so hard for women around the world
to give birth?
Why are things like sickle cell disease and
lactose intolerance more common in some parts
of the world than in others?
Why is it so incredibly easy for us to gain
weight?!
Along with many of my medical school classmates,
I have often wondered aloud about questions
like these. My professors’ stock answer?
“Evolution!”
That may fit on a bumper sticker, but it’s
not enough to address the complexities of
human life encoded in just that one word,
“why?”
However, a field of scientific study is emerging
that focuses on finding answers to the questions
I just asked and others that have avoided
easy answers.
It’s not taught at most universities or
medical schools, and many physicians would
be hard-pressed to describe anything about
it. Yet it holds the potential to improve
our health and eradicate many of the diseases
that plague us today.
That field is evolutionary medicine.
It links the processes revealed by Darwin
in the nineteenth century to address twenty-first
century questions in medicine.
It will only take me a few minutes to explain
what evolutionary medicine is and why we should
care about it in this opening episode. In
future episodes, we will cover current applications
and explore future possibilities and directions
for the field.
My name is Florence Yuan, and this is Darwin,
MD!
[Darwin, MD jingle]
So, what is evolutionary medicine anyway?
Evolutionary medicine, also known as Darwinian
medicine, is a field of study that examines
human health and disease using evolutionary
principles and the evolutionary history of
humans as a species.
The field formally emerged in the early 1990s,
and scientists commonly credited as its “founders”
are George Williams, Randolph Nesse, and Stephen
Stearns .
Medicine is generally studied and taught from
a molecular and physiological point of view,
looking at the microscopic mechanisms of how
cells and signals and hormones and genes all
interact to make our bodies function or cause
disease.
These close-up descriptions of biochemical
processes are known as
proximate causes or explanations. And these explanations are important!
But they don’t tell the whole story.
This is where evolutionary medicine comes
in. Evolutionary medicine, or “evo med”
as I like to call it, aims to determine what
are known as the ultimate causes of health
and disease. Rather than looking at the immediate
mechanisms behind a characteristic or process,
ultimate causes look at the broader and higher-level
reasons why something happens the way it does.
In the case of evolutionary medicine, that
usually involves looking at the history of
the human species, its primate relatives,
and other organisms important in human evolution.
After hearing this, you might be thinking.
If evolutionary medicine bases its conclusions
on millions of years of evolutionary history,
how is it supposed to be relevant to a regular
person like me?
That’s a great question, and probably one
of the reasons why evo med isn’t as well-known
as it should be. At first glance, it doesn’t
seem applicable to the average person.
This whole series aims to prove that idea
wrong, but I’ll start by listing just a
few examples of how evo med is relevant to
people like you and me.
Evolutionary medicine can show how many of
the chronic diseases we have today result
from culture changing much more rapidly than
biology can evolve .
For example, evo med can inform the discussion
about obesity and type 2 diabetes, both of
which have become global epidemics as high-sugar
and high-fat foods have become plentiful.
We can use the evidence evo med gives us to
debunk the “Paleo” diet and figure out
what kinds of foods we should actually eat.
Evo med can also reshape the way we look at
certain human characteristics.
For example, the ability to digest milk in
adulthood, commonly seen in the Western world
as normal, actually evolved from genetic mutations
in certain European and African populations
in response to cattle domestication. This
means that those of you who are lactose-intolerant
may actually be the “normal” ones!
One of the topics where evo med truly shines
is in childbirth and parenting. Evolutionary
medicine can inform parents’ decisions about
when and how to give birth, what medical and
non-medical support tools are most beneficial
for both mother and newborn, how to prevent
allergies and other diseases, and so on.
These are only a few of the many ways that
evolutionary medicine contributes to scientific
knowledge and can help us throughout our lives.
These topics and others will be the focus
of future episodes.
As with any science, evolutionary medicine
comes with its own language, so to speak,
of terms that define and describe key concepts
in the field. It’s important to establish the
definitions of these terms in order to have a
foundation for what we will be talking about.
Let’s start with perhaps the most central
concept in evolutionary medicine: evolution.
Evolution can be defined as changes in the
inherited characteristics of organism populations
over time. Such changes are maintained by
a process first described by Charles Darwin
called natural selection, in which organisms
better suited to their environment are more
likely to survive, reproduce, and pass on
those adaptations to their offspring.
Two terms that are crucial to understand for
evolutionary medicine are the concepts of
trade-offs and mismatches.
Evolution deals in trade-offs, where a benefit
in one area or during a particular period
of an organism’s life can often lead to
some sort of harm or disadvantage in another
area or time of life.
For example, the evolution of cells to optimize
growth and survival through early reproduction
may lead to cancer later in life when that
growth continues after reproductive age .
Evo med also commonly focuses on mismatches,
where adaptations designed for one environment
become irrelevant or even maladaptive in a
new and different environment.
For example, the rapid increase in the incidence
of allergies and autoimmune diseases in recent
decades may come from us excessively sanitizing
our environments and getting rid of microbes
that are actually important for the development
of our immune systems.
A lot of the terms I just talked about require
a little more context than I can provide in
this series. A basic understanding of research
design, genetics, biostatistics, and cell
biology can be helpful to more deeply understand
what we will be talking about.
Let’s look ahead now to some of what’s
to come in future episodes.
We’ll be structuring each episode around
clinical cases, since they allow us to learn
about broader concepts in evolutionary medicine
through the lens of individual patients’
stories. You’ll hear about a patient who
presents to you with a particular condition,
and then I’ll give you the background information
about evolutionary medicine that you need
to properly evaluate the case.
This is how medical students and doctors across
the U.S. learn about various diseases and
how to treat them. The process of thinking
through the reasons for a specific diagnosis
is part of what makes medicine so interesting
and exciting.
I hope you’re looking forward to it! See
you in the next episode.
[credits]
