>> Kevin Coots: Thank you for coming. My name is Kevin Coots, and I'm
here to welcome Daniel Lieberman to the Microsoft Research Visiting
Speakers Series. Daniel is here today to discuss his book: The Story
of the Human Body: Evolution, Health and Disease. The human body has
undergone numerous changes over millions of years. While all this
evolution certainly brings benefits such as greater longevity, it's
also helped create conditions our bodies can't handle like obesity and
Type II diabetes.
Daniel Lieberman is
Lerner Professor of
for his research on
especially barefoot
Professor of Human Evolutionary Biology and a
Biological Sciences at Harvard. He is well known
the evolution of the human head and on running,
running.
His research and discoveries have been highlighted widely in the media.
Please join me in giving him a warm welcome.
[applause]
>> Daniel Lieberman: Thank you so much. It's a real pleasure to be
here. Now if I stand here will I be able to -- is this okay? Okay.
And can you -- okay, I guess I'm micced. So, first of all, thank you
for inviting me it's an honor and pleasure and I find it a little bit
bizarre to be here at Microsoft. This is sort of fabled place. I
spent a lot of time working in parts of the world where computers don't
even exist. So it's fun to come to the other extreme. In fact, we try
to bring computers every summer to the places we work at in Africa.
So it's fun to experience this amazing place. So I'd like to talk
about a question or actually a pair of questions that have evolved over
the last 20 or so years since I've been teaching human evolution. When
I first started teaching human evolution, I was pretty much fascinated
with and focused on telling the story of the human body in terms of the
family tree. You know who beget whom. Teaching students about
australopithecus afarensis,
Australisafricanus and homohabilus homoerectus and all that kind of
stuff and the dates and who found them.
And over the years I've become more and more interested not so much in
that story but rather the story of how the body itself has changed.
And also why that's relevant. And a large extent, to a large extent
that's because of the questions that my students ask.
After all, most of them don't become like me, professors, most of them
go on to become doctors or software engineers or whatever. And they're
not going to remember the minute differences between one species or
another species but they all have bodies and they all use their bodies
and they all care about how other peoples' bodies are functioning.
So my book really is an attempt to try to answer two questions, which
have sort of arisen over the years in my teaching and one is and my
research which is why is the human body the way it is and the second is
why is that relevant, why should we care about that evolutionary
history. I'll try to briefly summarize some of my thoughts.
And the first 150 or so pages of the book actually tells the
evolutionary story of the body, and obviously there's no way I can do
that in a 35, 40-minute lecture. Let me briefly summarize that I see
five major transformations that really caused our bodies to diverge
from essentially a chimpanzee-like creature 6 million years ago up to
the bodies we have today. The first ones are origin of bipedalism.
Our very first ancestors appear to have been bipeds, apes that walked
on two legs. And another major shift occurred around 4 million years
ago with the genus Australopithecus. You heard of Lucy, a famous
Australopithecus. And she was adapted to more open habitats, eating
diets other than fruits all day, because chimps basically all they do
eat is fruit, 90 percent of their diet is fruit.
Around two, two and a half maybe 3 million years ago there's a shift to
hunting and gathering with the origins of the genus homo. Brains get
bigger. People start cooperating and processing their food. They
start running and throwing. Modern bodies more or less evolved then,
but that wasn't the end of evolution of our bodies because the
descendents of homoerectus grew even bigger brains and larger bodies
and slowed down their rate of reproduction and probably became fatter
and all kinds of transformations.
And the final major shift was actually just a small one from an
evolutionary perspective, the origins of our own species, homo sapiens.
And we're basically very much like Neanderthals and other archaic human
cousins except we differ primarily above the neck.
But of course what happened above the neck in humans, especially in our
brains and our ability to communicate through language, had major
effects on, of course, the entire world and still is today. So that's
like a 5-second, maybe a 5-minute intro to everything that happened in
human evolution. Now let's move on.
Because let's just assume you've read all those chapters, you
understand it all, and let's think about the consequences of those
shifts. The important point if you stand back from all those five
transformations, each of which was an improbable event, many of them
driven by climate change. If you stand back what we end up with is a
creature like us that was evolved to be bipedal, slightly fat, so
typical chimpanzee or typical ape has five or six percent body fat, but
even lean human beings, hunter gatherers super models, have maybe 10,
15, maybe even 20 percent body fat. We're very fat species compared to
most mammals. We're furless. We're sweaty. We're big brained.
Dependent on tools. But of course the other factors that we're very
interested in today is our diet and activity adaptations.
So we're adapted to either diet that's very high in fiber low in
carbohydrates. But we're also adapted to crave energy. We love sugar,
fat, love starch. We're also adapted to be highly physically active.
I'll show you some data there in a second, but we also adapted to enjoy
comfort and to enjoy rest whenever possible. And it's these
transformations, of course, that are very important in today's world.
So humans didn't stop evolving when we evolved, when our species
involved around 200, 250,000 years ago. Evolution has been continuing.
And it's even going on today. After all, natural selection is the
outcome. Emergent property of heritable variation. So variations that
you inherit from your parents and differential reproductive success
that's related to those variations, individuals with variations that
cause them to have fewer offspring or more offspring than result in
change from one generation to the next in terms of the percentage of
those genes.
And so it's still going on. There's actually evidence for natural
selection going on today. Like one of the biggest studies I was
talking to somebody from Framingham, one of the biggest studies going
on today is the Framingham Study where people actually are documenting
selection that's occurring right now in our lifetime.
But so although natural selection is still going on, anybody with who,
if space aliens came to earth and to observe us for a while what they'd
most notice is our cultural behavior. And there's another form of
evolution going on that's also incredibly important, cultural
evolution. Culture is essentially what we learn. You learn culture
from your parents, learn it from each other, the Internet, reading a
book or going to lecture and cultures change over time. They change
rapidly. Think about the last 5,000 years or so of changes in text and
script. It's been amazing transformation. And a lot of it going right
on here at Microsoft, still being transformed. In fact, probably what
makes this as an important company is its role in cultural evolution,
if you really think about with the Internet age.
So it's a very important force. But if you stand back from the details
of what's gone on since our species have evolved, I would say there's
two really big transformations that sort of stand out. This is broad
brush, the first, of course, is the origins of farming. The
agricultural revolution, which actually happened seven times
independently. The first incidents of agriculture about 10,000 years
ago in the Middle East, also the same time in China and elsewhere in
different parts of the world and of course that transformed the world
in terms of the food we get. We get a lot more food. We have much
larger population sizes. But also people started living in cities and
towns and surrounding themselves with their own waste products and
interacting with animals and getting diseases. So along with more food
and more people also came a lot more infectious diseases. And the
other sort of huge transformation was the origins of the Industrial
Revolution, as well as modern science. Those happened hand in hand.
They were interrelated. And through industry we've been able to
generate more food and of course there's been incredible population
explosion; and at first, as cities started to swell, infectious disease
rates went up even more. But then with the invention of sanitation and
antibiotics and various other aspects of modern medicine we've now
become able to combat many of those infectious diseases that were
unleashed initially by the agricultural revolution and then became even
more important during the industrial revolution.
So arguably today is the healthiest era in human history. And let me
give you a few bits of information to try to convince you of just how
good it is today. So one important fact is or measure of health is
infant mortality.
So today, in developed countries such as the United States, infant
mortality rates are at less than 1 percent. But that's actually very
unusual for most of the human evolutionary history. We know during the
paleolithic, infant mortality were pretty high. We can estimate them
from population size estimates from the fossil record. And when
farming evolved, although people had more offspring because they were
able to have them more rapidly, infant mortality rates were still
extremely high about 30, 40 percent, reasonable average. A lot of
variation around these numbers. It's only been very recently, as I
said, really since the invention of penicillin and antibiotics that
infant mortality rates have plunged like what we have today.
Adult mortality is also a case. If you survived childhood, turns out
many people think that hunter/gatherers lived horrible nasty lives.
It's not true. If they survived childhood, they lived to be pretty
old. Lived to be in their 60s and 80s. It was with the origins of
farming that mortality rates started to plunge precipitously as people
started dieing from all kinds of infectious diseases and malnutrition
and famine and all those things that affect farmers. And it's only
again since, mentioned modern medicine and sanitation and various other
wonderful things that, again, mortality rates have climbed back up
again. And actually we're not too different from our paleolithic
ancestors. Again if you discount infant mortality that occurs during
childhood.
So the end result of this, of course, is growth in world population.
So the world was pretty unpopulated until the origins of farming. Then
it started to increase very slowly. This is in billions, by the way.
Of course with the Industrial Revolution there's been an incredible
accelerated increase in population. Today the world has more than 7
billion people. I guess the best estimates are by the end of the
century we should have more than 9 billion people on the planet. All
of this of course is a result of lots of people having lots of babies
who survive.
But there are other ways of measuring health. A good one is stature.
So all of us have a certain genetic potential to grow to. There's
many, many genes which influence how tall you're going to be. But not
all of us reach that height because usually insult to our growth. So
if you have infections or malnutrition or other problems, you don't
actually reach your genetic potential. So height actually turns out to
be a really useful measure of overall health. And so this is a graph
of height of males in Europe. I've actually taken French males since
Napoleon and this guy over here, and these are European paleolithic
males and you can see that during the Ice Age, during the paleolithic
people were about 5'8" inches in Europe. And during farming again
health declined precipitously around the world. People shrank down to
about 5'4". Here's Napoleon. We all know a famous shrimp. And then
height started to increase again with the Industrial Revolution. Now
actually we've not only caught up but we've slightly exceeded, even in
France, their paleolithic ancestors. The average frenchman is 5'10".
>>: [indiscernible] homo sapiens.
>> Daniel Lieberman: Homo erectus varied a lot in height depending
where they were. Homo erectus was a species that evolved around 2
million years ago and died out, went extinct in different parts of the
world. There are ancestors. In Africa for example homo erectus was
pretty tall. There's examples of homo erectus in populations in some
parts of the world that were much shorter. In the caucuses they were
quite short. There's lots of variation of height in the paleolithic
just as there is today. A lot of that driven by selection.
But the important point is that although health is doing well today by
many markers, we could also be clearly doing a lot better. And the
best way of encapsulating this is what's called the epidemiological
transition. Some may have heard of this. If you stand back from the
last few hundred years, look at what's happened recently, we know
there's been an incredible decline in death illness that comes from
infectious diseases as well as malnutrition.
Our ancestors were much more likely to die of plague and smallpox and
tuberculosis and infectious diseases such as that. Most of us don't
even worry about that anymore. But what's risen in concert with that
is not infectious diseases. So today we die from cancer and from heart
disease and osteoporosis and Type II diabetes and various autoimmune
disease disorders. These are all on the rise. Lots of evidence
they're on the rise. Some have seen the famous graphs. It's plastered
all over the place. Hard to go anywhere without seeing graphs about
the shifts in obesity around the world. But suffice it to say that
during my lifetime the percentage of people in the United States who
are obese has more than doubled. And along with that has been the rise
in a whole series of other diseases such as Type II diabetes going up
in the U.S. and also going up and even faster rates in many developing
countries such as China or India where diabetes rates are climbing at
really alarming rates.
Breast cancer, the list goes on, of noninfectious diseases whose
incidence is going up. I'm not talking about death from these
incidents. I'm talking about the incidence of these disease and
there's a whole series of other diseases people are getting, myopia and
cavities and lower back pain and flat feet and various mental health
issues and acid reflux. We don't have a huge amount of data on them
like Alzheimer from the paleolithic, but good evidence that they're
becoming much more prevalent today. I'll show you more evidence of
that in that in a second.
Is this just the price of progress? People people would think, of
course, if you're not going to die from smallpox or the plague, we're
actually lucky to be able to live to be old and die from cancer or
heart disease. This is actually a trade-off if you're living longer.
To some extent that's actually true. For example, think of cancer,
cancer is a disease caused by mutations and mutations accrue with time.
So as you live longer you're more likely to acquire mutations to some
extent.
But it turns out that if you look at the evidence, that's only a
partial explanation. Because -- and one of the major reasons for that
is that it's very important not to confuse diseases that are more
common as you age with diseases that are actually caused by aging.
And so, and the hypothesis from the field of evolutionary medicine and
evolutionary medicine is the field of essentially applying evolutionary
theory, Darwinian biology, to medicine and disease. So the
evolutionary medicine hypothesis, and if you know this wonderful book
by Nessy and Williams: Why we get sick. What started this field, is
that many of the health problems that people encounter today, these
noninfectious diseases, and actually many infectious diseases as well,
are what we call mismatch diseases. It's an important term. If
there's any term you remember from this lecture I hope it's mismatch
disease. Those are defined as diseases more common more severe because
our bodies are inadequately or poorly adapted to novel environmental
conditions in which they experience. And so I actually as an
experiment try to list all the mismatched diseases that I think are
common today in our culture and it was a pretty unpleasant task, let me
tell you, and I should mention that this is, I use the word hypothesize
for a reason because we lack a lot of good data on hunter/gatherer. We
don't know, for example, about ulcer rates or pre-eclampsia among
hunter/gatherer populations, but there's compelling arguments to
believe many of these diseases are more common or sometimes even novel
because of the environmental conditions in which we live in. And, by
the way, this is just, these are just the noninfectious diseases. Had
I put in the infectious diseases that have arisen since the origins of
agriculture this would be a really truly scary horrible list. I've
left those out. If you think these diseases aren't important, the
chances most of us in this room are going to decide from mismatch
diseases. The number one cause of death today is coronary heart
disease, kills about a third of Americans. Evidence shows that
coronary heart disease used to be extremely rare to nonexistent among
hunter/gatherer populations. Cancer is ancient. Dinosaurs have cancer
and dogs get cancer. It's not a novel disease but the evidence clearly
is that cancer rates have been rising particularly many kinds of cancer
around the world. So that's another mismatch disease, and cirrhosis,
Type II diabetes, metabolic, hypertension, osteoporosis, these are all
common diseases today that are costing us billions. But which are
mismatched diseases. In fact, if you think of United States today
there's a big debate about healthcare we spend about two and a half
trillion dollars a year on healthcare the estimates are about
70 percent of the disease that we treat in the United States is
preventible, and I would argue that almost all of those are mismatch
diseases. So we're confronting an epidemiological transition that's
costing us an enormous amount not only in terms of money but in terms
of misery. So the origin, so why we get sick from these diseases is
important. But I think an equally important perspective is what do we
do when we get sick from these diseases. And here's where I think the
importance of cultural evolution comes in because how we respond to
these diseases is setting up an interesting new dynamic. So many of
you may know that I'm interested in running and barefoot running and
feet so I have a bit of a foot fetish. I'll use a foot example to
explain this. We obviously evolved to be barefoot. Until recently
shoes didn't exist anywhere on the planet. When shoes were invented
they were very minimal. So our bodies were adapted to be either
barefoot or wearing very minimal shoes. Okay. So what happens, well,
we invented all kinds of novel shoes looking around the room I see
quite an interesting variety of shoes here, many of the shoes we invent
are cushioned and comfortable and sexy and have all kinds of features
we like about them but there's also no question that those shoes cause
a variety of problems including flat feet. So I work with barefoot
populations around the world. I can tell you that barefoot people
don't get flat feet. It's almost completely nonexistent. We can make
a very compelling case that flat feet are caused by shoes which cause
your feet to become weak so you don't develop an arch or it collapses.
That's a mismatch disease. Not a serious one, but nonetheless a
mismatch disease.
What do we do, we go see a podiatrist, gives us an orthotic. Nothing
wrong with that. It basically replaces the natural arch of the foot.
It's fine. You can live with a flat foot. Probably a third in the
room have flat feet and wear orthotics. Maybe because it's Microsoft,
maybe it's a bit more than a third. I don't know. Sorry. That was a
cheap dig. But the point is that that what happens that sets up a
vicious circle because we can get away with flat feet, right, we can
then continue to have the shoes that cause our feet to be flat and keep
the cycle going. So we don't pass on flat feet to our children
although there's a genetic, there's some genetic proclivity towards
flat feet but those genes aren't novel genes that have swept through
the United States in the last few generations causing an epidemic of
flat feet. What's happening is ancient genes interacting with modern
environments and we're basically continuing the cycle. I think the
cycle is so important, so vital to think about that I think it deserves
a term. Now I'm not the first person to come up with this idea of this
vicious cycle, but I would propose that we call it disevolution; dis
for bad and evolution for change over time.
Another example would be something I work on. I work on heads as well.
If you eat very soft processed food, you don't chew very much, chewing
is necessary to grow a proper sized jaw. If you don't grow a proper
size jaw, your third molars, wisdom teeth, can't go in. They get
impacted, go to an oral surgeon, get them removed enables us to eat
food all day, doesn't require much chewing, keeps the cycle going on.
My hypothesis is that this vicious circle, this dynamic, disevolution,
is a really important cause of the underlying epidemiological
transition that we're experiencing. And let me try to give you a few
bits of criteria by which to judge this. So characteristics of
mismatch diseases that generate this kind of feedback loop are, first,
they're caused by gene environment interactions. Pretty much all
diseases have a genetic basis to some extent to them.
But what's changed is not the genes it's the environments that have
changed. I think that's not a pretty noncontroversial statement.
Secondly, for most of these diseases the environmental causes of them
are very hard to perceive. They're incremental. They happen
step-by-step. There's no obvious relationship between cause and
effect. Like all of you folks are sitting very comfortably in these
chairs and that probably all of you are aware of the data that sitting
in chairs ain't good for you. We do it, nonetheless. And sitting in a
chair for an hour is not going to cause you to decide instantly. But
keep doing it over and over and again, hour after hour, day after day,
year after year, decade after decade, the problems caused by sitting in
chairs accrues very slowly.
Third, I don't think anybody's died from sitting in chairs. Most of
the diseases that we get from this mismatch don't affect reproductive
success, they don't tend to occur to us until we've had not only our
children but often our grandchildren, we're already quite old. They
don't really affect how many offspring you leave and who then survive
and have offspring. And finally all of them are based in causes that
have trade-offs. There are benefits to chairs, for example. They help
you sit at a computer, for example. I'm sure people in this room are
very interested in that. So there's always trade-offs, everything
involves trade-offs. Let's look at three different kinds of examples
of this vicious circle, and I'll first start with environmental changes
that involve too much of a stimulus and we'll talk about environmental
changes that involve too little of a normal stimulus and then finally
environmental changes that create too novel a stimulus. Let's start
with too much, because that's on everybody's mind today.
So one of my major arguments is that we evolve to be sort of gas
guzzlers of the primate world. We're very energy intensive species,
even hunter/gatherers. And that actually, that transformation really
started around two, two and a half million years ago with the origins
of the genus homo. When brain size started really increasing rapidly.
Brains are very expensive tissues. If you're sitting here listening to
me, you're using about 20 percent of your body's resting metabolism
just to pay for your brain. If you're dozing off, you're still using
20 percent of your metabolism to pay for your brain. Brains are costly
tissues, guzzling vast amounts of energy all the time. Big brains are
very expensive; you have to pay for them. Big brains are costly, but
an even more costly aspect of our biology is our reproductive strategy.
We evolve from creatures sort of ape-like, they were apes and they
probably reproduced about every six years.
A chimpanzee has offspring every six years. But hunter/gatherers are
able to have offspring every three years. So basically they can double
the rate at which they pump out babies. Not only do we pump them out
faster, which takes a lot of energy, because each baby costs a lot of
energy, we also grow them more slowly. So here's Prince William, for
example, at the age of about 13 and you can see that he's still not
even shaving, but if he had been a chimpanzee he would be an adult,
ready to have, starting to breed, and have offspring.
We have extended our period of, the trajectory of development, slowed
it down incredibly by about 50 percent, adding an enormous amount of
cost to raising a child to become reproductive. We slowed it down.
Made them more costly with bigger brains and bigger bodies, pumped them
out faster which takes a lot of energy. This is a very
energy-intensive system. And how did we get the energy to have this
kind of biology. And the answer is, I mentioned it before, hunting and
gathering. Hunting and gathering didn't occur all at once, like 2
million years ago, like somebody invented it like the computer. It
evolved probably very slowly. But it involves the combination of a
number of important human behaviors, making tools, for example, which
really takes off around two and a half million years ago. Food
processing. Hunting, which didn't really start until around then.
Endurance running, one of my passions, begins around then. The ability
to throw spears, for example, in order to hunt, starts around then. We
also know there must have been important division of labor and intense
cooperation and all these things combine together to create a novel way
of life that enables hunter/gatherers to get more energy than their
ancestors were probably able to do. And importantly the food that
provides that energy were foods that were high in carbohydrates and
high in fat. Hunting and gathering, things like tubers or honey. So
we're very dependent and we crave as a species carbohydrates and fat.
And for millions of years our ancestors got them through hunting and
gathering but the origins of agriculture transformed our ability to get
these resources. We started to grow them. Around -- the oldest
farming is from the Middle East and from China. It's only been around
for about 600 generations, number of generations of dogs that have come
and gone since the time of Christ. Not a lot of generations. And
we've transformed what we eat. Pretty much everything we ate today, I
had a nice lunch here at the cafeteria in Microsoft and all the food I
ate was domesticated, probably from a few resources. And the last few
generations we created industrialization of food. Grow meat like we
build cars. We're able to turn corn into sugar and that's of course
further transformed our ability to get carbohydrates and fat in just a
few generations. So important examples of this are, for example, how
much sugar and fiber we eat. So hunter/gatherers don't get a lot of
sugar. Most of the wild fruits you get out in, say, Africa are about
as sweet as a carrot. I can tell you this from personal experience.
They're not that sweet. And they come loaded with a lot of fiber. The
only sort of high sugar food that hunter/gatherers can get is honey.
They don't get as much as they like. So estimates are paleolithic
hunter/gatherers got about four to eight pounds of sugar a year. We
know today Americans, we grow it by droves, we turn our corn into
sugar, the average American gets about hundred pounds of sugar a year.
Importantly, that sugar we get today is not, has -- the sources of
sugar had the fiber removed. Typical hunter/gatherer eats about 80
pounds of fiber a year 12. That's normal. Typical American eats about
12 pounds of fiber a year. We think that's normal today. But it
isn't. The reason it's a problem is because of food processing and how
that affects the way we metabolize foods. So carbohydrates are broken
down into sugars or just had the sugar raw. And it enters our body and
it gets converted either into glucose or fructose, and glucose goes
straight into your bloodstream, causes an insulin response. And foods
that are high in glucose but also low in fiber go very rapidly into the
bloodstream, cause a rapid spike in blood sugar levels which cause a
rapid spike in insulin levels which then cause a crash in blood sugar
levels, which leads to more eating. And also leads to various
problems.
Fructose has to go to your liver. Your liver can't handle that much
sugar that fast because in the absence of fiber, because fiber slows
the rate at which the sugar gets into the bloodstream. So foods that
are very high in sugar, low in carbohydrate, basically present a kind
of double whammy to our bodies and they create what's called metabolic
syndrome, an increase in belly fat and cholesterol and blood pressure
and blood sugar rates. There's a wonderful recent book about this
called Fat Chance by Robert Lustig which explains a lot of the biology.
This leads to a variety of diseases, one being Type II diabetes. It's
a gene caused by interactions between our genes and our environment.
There are genes which predispose some people towards being more likely
to get Type II diabetes than others. But it's the environment that
really causes these diseases to become much more common. And so, for
example, high amounts of central adiposity, belly fat, essentially, is
a major risk factor which leads to insulin resistance which is when the
cells in your body are no able to sense insulin, which then, which acts
to basically take sugar from out of your blood and basically into your
cells. So what happens is you set up this vicious circle. We get high
levels of blood sugar. Insulin levels spike because they're trying to
get the blood sugar out of your body. Blood sugar is very toxic in
overly high levels. Eventually your pancreas wears out, which means
that blood sugar levels remain high and insulin levels remain high and
eventually the whole system crashes. So what do we do about Type II
diabetes? We have two major responses. One is through medication.
There's lots of drugs out there which help treat that system I just
showed you earlier, but of course the other thing we prescribe is
exercise and good old-fashioned sensible diets. And both of these are
important ways to treat Type II diabetes. The important point to
remember, and it's very insightful point, but medication of course
doesn't cure anybody of diabetes, helps mitigate the symptoms. Allows
people to live with the disease. But exercise and diet actually can
prevent diabetes. And, in fact, in extreme cases it can cause the
disease to go into remission. You can actually reverse diabetes with
serious exercise and very good diet. And of course there's lots of
other benefits from exercise. I would argue that because of this
feedback loop, when people don't use exercise and diet as much as
medication to treat diabetes, it's become a disease of disevolution,
where we have a gene environment interaction in which, yes, there are
some genes which predispose some people more to diabetes than to
others, but those genes haven't just suddenly swept through human
populations, it's environmental shifts that are causing diabetes to
become more common. Then the causes of diabetes are very incremental
and nonobvious. When you have orange juice for breakfast you don't
feel the diabetes coming on just from drinking that orange juice. Or
not going for a run. The disease has little or no effect on
reproduction because most people don't get the disease until after they
reproduce, often when they're grandparents. And there's a trade-off
between the costs and benefits of the environmental shifts that have
led to diabetes in the first place. So there are many other examples
of diseases of too much, but let's move on to another example of
diseases of too little. And it's axiomatic in biology that almost
every system in our body requires stress to grow properly. I don't
mean like social stress getting up in front of a bunch of people, them
not laughing at your jokes, for example, that's very stressful.
What I mean by stress is environmental stimuli that require your body
to have to work harder. And there are many examples. And one example,
of course, is your muscular system. We all know that, for example, if
you want to grow bigger biceps, you have to lift heavy weights which
causes essentially muscle damage, which then elicits a response of the
muscle then hypertrophies and grows. No strain, no gain. Sometimes
people say no pain, no gain is a real phenomenon. It's necessary to
allow capacity to match demand. Muscles are very expensive. About
40 percent of most people's metabolism is used to pay just for the
muscle in your body. If you're not going to be using it and you're in
an environment where energy was limited, which is what was the case for
most of human evolution, it's best to get rid of it when you don't need
it. If we don't use our muscles as our former governor of California
experienced, you lose that muscle mass. That's a natural tendency.
And that prevents overcapacity. It's evolution's way of matching
capacity to demand properly. While there's lots of examples of stress
that are important and perhaps none are more important today to talk
about than physical activity, which is well known to have a variety of
effects on many systems of the body on stress, your cardiovascular
system, your muscles, your digestive system, your immune system,
physical activity turns out, the stress it causes, incredibly important
for neural biological health as well related to Alzheimers and
depression and anxiety and even the ability to learn and remember
things.
But the important point is that the importance of physical activity in
human health is not a coincidence. I would actually argue it's because
of evolutionary history. Because part of hunting and gathering
involves being an athlete. Our ancestors who were apes probably didn't
walk much. Typical chimpanzee walks about two to three kilometers a
day, maybe climbs about 100 meters a day in trees. If you go watch
chimpanzees, they spend half a day putting food in their mouth and
digest it and then fill their guts again. They actually spend
50 percent of the day eating. Again that's what used to be normal.
Gorillas actually spend even less time moving about. They actually
travel about a kilometer a day. But average hunter/gatherer, worldwide
average average, average female hunter/gatherer travels nine kilometers
a day, average male hunter/gatherer travels 15 kilometers. So five to
ten miles a day. To put that into perspective, your average
hunter/gatherer goes at least from LA to Washington, walking, every
year. And they work every day. They do physical activity every day
where they do walking, running, climbing, digging, throwing, no bank
holidays, no weekends, there's no retirement. This is what life was
like until extremely recently. And one way to measure that is there
are many ways to measure physical activity. Very simple way called a
physical activity level or PAL. Physical activity level the total
amount of energy you spend every day divided by the amount of energy
that you need to maintain your body. So basically how much energy you
spend if you're in bed basically doing nothing in a perfectly climate
controlled room. So most hunter/gatherers have physical activity
levels, there's a lot of variation, I'm simplifying horribly, but the
average is about 1.9. They spend about as much energy using their
bodies as they spend maintaining their bodies. So subsistence farmers,
a little harder working than hunter/gatherer, they average about two.
There's huge variation around these numbers. But people who live
sedentary office lives, like me, have physical activity levels of about
1.5 to 1.6. That's an enormous reduction. That's a greater than
15 percent reduction. And there are many examples. And one example
that I kind of like is sewing machines. Of course back in the
paleolithic people sewed they sewed by hand. And then with the
industrial revolution people invented the, Singer invented the sewing
machine which has a pedal, grandmother actually used one of these,
pedal that moved the motor. Of course now we have electric sewing
machines and folks measured, they put oxygen masks on people using
different sewing machines and doing everything else you can imagine.
Turns out that a pedal sewing machine costs you about 98 kilocalories
an hour and the electric sewing machine here used by the mayor of
London, I'm not sure if he's really sewing, uses about 70 kilocalories.
15 calories an hour, that's like nothing. Right? Imagine these folks
are unionized so they're only working five days a week, eight-hour
days, 50 weeks a year. That adds up to 52,000 calories a year which,
by the way, is enough energy to run 18 marathons. And that's just
putting an electric motor on a sewing machine. Now add in escalators
and elevators and shopping carts and all the other conveniences in our
lives, we have transformed human work in the last few generations like
we've never transformed it before and it has incredible effects. Think
about it, we actually -- the estimates are we spend about 300 to 500
calories less per day doing physical activity than our grandparents.
That's an amazing, astonishing transformation in human biology. And
there are many effects of that physical activity. I'm just going to
pick out of the hat one of them I'm very interested in, that's
osteoporosis. This is a disease that's basically unknown among
hunter/gatherer or subsistence farmers but rising around the world at
alarming rates. In the United States 30 percent women over the age of
50 and 10 percent of men over age of 50 are now diagnosed with
osteoporosis. It's rising everywhere. Very alarming disease. It's
caused by forces affecting growth. This is the guy that won the US
Open, Raphael Nadal. His left arm is much thicker than his right arm
because that's the arm he uses to tennis with, holds the racquet.
Genes in left and right arm are the same. I don't think he's a
chimera. And he's got a lot more muscle mass in his left arm, has
thicker bones, because the bones actually respond to loading. We know
that bones again experience that trade-off just like muscles. If
you're using your bones a lot, you want them to grow thicker so they
can handle the loads. And if you are not using them very much they'll
waste away, they'll grow thinner. Astronauts go off into space, get
osteoporosis because their bones waste away in micro gravity.
So this relationship between physical activity and bone growth,
however, comes up against a very ancient constraint and that constraint
is we grow our skeletons when we're young and we lose skeleton mass as
we age. That's just the way mammals are. Sorry. There's nothing we
can do about it. So most of us hit peak bone mass between about the
ages of 20 and 30. And as we discussed before, people are more active
when they're young, acquire higher peak bone mass. They build better
skeletons. And we all lose it as we age. And if you're a woman, you
lose it at a faster rate once you go through menopause, because of
estrogen. Estrogen plays a protective role for bone health.
Individuals who are inactive grow less peak bone mass and they can also
lose their bone at a faster rate than people who are active. And the
end result is that inactive people are much more likely to fall below
the bone mass threshold that leads to osteoporosis. That's why
osteoporosis is on the rise. Another example of disevolution. Disease
caused by interaction between genes and our environment. And it's not
like genes for osteoporosis suddenly swept through our culture, our
population. It's our environmental changes caused by electric sewing
machines and cars and shopping carts and all kinds of other things.
And every time you use a shopping cart you don't think, oh, my gosh
it's contributing to my osteoporosis; you can't even feel its effects
on your bones. But the incremental effects add up slowly, slowly, bit
by bit over the years. It has no effect on reproduction because most
people don't get the disease until they're grandparents. And there's
many benefits to cars and shopping carts and elevators. There's a
trade-off for all these things. I'm not saying we should get rid of
cars or shopping carts, but we should understand that everything
involves costs and benefits that get traded off. Finally, diseases
caused by things that are too new. We are aware the fact that our
environments are filled with novel stimuli that we never experienced
when we were, in the old days, like bungee jumping, cars, cigarettes,
various kinds of pollutants in our environment. You could add
computers as well. And there's no question that we're not always well
adapted to those aspects or environments. So here's an example.
Here's a gentleman who looks like a perfectly respectable person, like
we all like to be this guy. Here he is. He's reading, sitting in a
nice comfy chair, wearing shoes. In actual fact all these things are
basically killers. Well, I mean, I'm exaggerating a little bit.
They're not killers but they all cause health problems. I'll pick as
an example, reading, because it's something we all care about
profoundly, right? So reading is obviously a very recent phenomenon.
We started around 3,000 BC. And it's only in the 19th century that
universal literacy really started to explode. And so now most people
read, at least in developed nations. And it's actually around that
time that people began to notice something was going on. So here's a
quote from James Ware, physician to the Queen's guard. And he noticed,
quote, among the Queen's guard officers many were myopic. From upper
classes. While of the 10,000 foot guards who come from the lower
classes, less than half a dozen were myopic, were nearsighted. And we
now know this is well documented all around the world less than three
percent of hunter/gatherers and subsistence farmers have myopia. This
is a very recent phenomenon in our environment. Some countries like
Asia some countries have a 50 percent rate of myopia, caused by having
an overly long eyeball. What happens is that light from photons from
me hit your eye, you focus them on your retina. But if your eyeball is
too long you can't focus them even more. Your lens and cornea can only
focus them so much so things that are distant are blurry. And there
are two interesting mechanisms that cause myopia, and there's a big
debate going on. One is close work. When you stare at something
that's up close, if you're myopic you're doing that all the time. And
glasses make things feel up close. You're firing these muscles in your
eyes called ciliary muscles. They attach to filaments that hold your
lens up. They have a wonderful name called the zonules of zin. I love
the name. It's irrelevant. But the point is that those muscles are
always contracting and the contracting increases the force and the
pressure in the main cavity of the eyeball, causes the eyeball to
stretch. It's thought that is one of the factors that causes overly
long eyeballs, and that's why people who stare into a microscope or
close work have their vision worsened. That turns out doesn't explain
all of myopia. There were gruesome experiments done back in the old
days when they would stitch the eyelids of animals shut, not to study
myopia, discovered these animals not doing close were, these eyes were
not being used at all developed myopia. And they developed overly long
eyeballs. Turns out there's stimuli clearly necessary from vision that
actually regulate eyeball growth. If you lack appropriate visual
stimuli your eyeball grows to long. Kind of some repressor mechanism
going on. And there are actually a lot of data that support this
hypothesis. Turns out, for example, children who spend more time
outdoors, regardless of how much reading they do, are less likely to
develop myopia. So the bottom line is that myopia is a complex
disease. There's no question it's caused by gene environment
interactions. There's people whose genes make them more likely to get
the disease, but obviously it's caused by environmental factors that
interact with those genes. Every time you read a book or don't go
outside doesn't -- you don't feel the effects on your eyeball length,
right. So it's very hard to figure out what actually even causes
myopia. Obviously has little or no effect on reproduction, thank God,
and no question that the benefits of reading outweigh the costs. Most
of us are not going to ban books because it causes myopia or for that
matter computers or all those other wonderful inventions. We're
willing to tolerate them. But, nonetheless, it's an example of
disevolution. What are our solutions? One is let's make our kids play
outside more. That's I think a no-brainer. Maybe we can develop books
and other visual stimuli that are more dynamic that are less likely to
cause that problem in the retina.
So finally, the last few minutes, I want to end with some thoughts
about how an evolutionary medicine approach, evolutionary perspective
can help us think about the future of the human body because there's a
famous expression by the great geneticist Theodosius Dobzhansky that
nothing in biology makes sense except in the light of evolution. The
field of evolution medicine we would argue that includes medicine. So
what's the perspective that we can get about this epidemiological
transition that can help us think about how we can decrease the burden
of noninfectious diseases as the burden of infectious diseases is
declining, right? Well, if you stand back from the details, I would
say there's four basic options available to us as a species. The first
option is to do nothing. Let's just let natural selection solve the
problem. A second is to invest more in treatment. Basically send NIH
more money, which is kind of difficult when the government shuts down
but anyway that's another story. We can certainly educate people more,
so they better understand how their bodies work, so they can make
informed choices, and finally we can change our environments. I would
argue of all of these we should do everything but the do nothing. That
I don't think is an option. For one, even if natural selection could
solve these problems, which is very debatable, it would take too long
for it to be of any practical use for any of the people we care about.
It would take hundreds if not thousands of generations. Furthermore
there's a lot of reasons why there's no necessary reason to believe
that natural selection is going to adapt us to high fructose diets
because it only works if they're heritable variations which actually
affect reproductive success. It's a very iffy statement.
I could spend hours talking about two and three and there's no question
we should do that. I think we don't spend enough on treatment. We
don't spend enough on education. But from an evolutionary biological
perspective there's reasons to be skeptical that we can do so much to
either. One is that a lot of the genes that are important in the gene
environment interactions that are used for pharmaceuticals, for
example, those genes tend to be of small effect and very numerous and
they also turn out to be very uncommon. So the gene that I may have
inherited that make me more susceptible for diabetes is not the same
gene that would make you susceptible to diabetes. And those genes
turns out they don't have a strong effect. These are diseases that
have multiple complex causes. And there's not going to be a Pasteur
for these diseases, which is why progress in solving many of these
noninfectious diseases can be very slow and incremental, as it has
been, and it's going to remain slow and incremental. I've been proved
wrong for some of these diseases, but that's everybody's best guess.
Education is also very important. But there's many reasons and many
studies which show that education is only so effective. For one, even
public service announcements are drowned out by about 27 to 1 by
advertisements for foods that are unhealthy, for example. More
importantly, even though we may know what's good for us, it's hard for
us to actually make decisions about that's what's good for us. For
example, when people are, when there's a stairway next to an escalator,
do you know what percentage of people take the stairway as opposed to
the escalator?
>>: Five.
>> Daniel Lieberman: Five percent. You guys are good. Turns out the
worldwide average I think is three percent and when you put a sign up
saying please take the stairway it doubles to about six percent. And
you know that's just human nature. If you were to put an escalator in
the Kalahari desert, the bushmen would do the same thing there. It's
normal. Because if you're on the threshold of energy balance makes
sense not to waste energy climbing the stairs because you can use that
energy to reproduce and to hunt, to do something that's going to
benefit you. The same thing is true if you put a piece of cake in
front of me and a piece of celery. Of course I'm going to eat the
cake. I've evolved to prefer the cake. It makes sense. Nothing wrong
with it. So overcoming those urges and instincts are going to be
difficult. Those interested in behavioral economics you may know
Daniel Kahneman book: Thinking Fast Thinking Slow, a lot of research
on this problem and they're hard to overcome. Education is only going
to do so much, which leaves finally the final shift is changing our
environments.
If you think about it, as I said before, we evolved to be bipedal and
fat and furless, tool using, but importantly we evolved to eat high
fiber diets low in carbohydrates, but to crave sugar, starch and fat.
Evolved to be very physically active but enjoy taking it easy when it's
possible. The problem is we never evolved to make the choices that we
now confront in our lives. So if you were able to travel back in a
time machine to this homo erectus family you would not hear that mother
or father telling their kid, okay, little Thag, don't forget to eat the
healthy food today and don't forget to exercise. Little Thag had no
choice but to exercise and eat healthy food. There was nothing else
for her to do. That was called life. If you didn't do it you died.
But today we have to nag our children to make the right choices because
we're surrounded by labor-saving devices and by calorie-rich food.
Especially without fiber and filled with sugar that make us sick. We
have this mismatch between ancient genes which we won't be able to
change and novel environments that we can change. And I think that's
where our big debate ought to be. Instead of having the debate we're
having today about healthcare, which is really about who is going to
pay, I think we should also be having a debate how we change our
environments and that's missing from the current debate. There's
really two current extremes. One view is coerce people, ban trans fats
and ban smoking and ban fast food from children's cafeterias and
require coercively physical education. That's one approach.
The other approach is to respect people's choices but to kind of help
them make the choices they would make that are in their own self best
interest. That's nudging. That would include things like sugar taxes
and signs encouraging people to use the stairs and Mayor Bloomberg's
Big Gulp ban. I would classify as a nudge. It was interesting how
people reacted so vigorously against Big Gulp ban. He wasn't banning
soda. He made it if you wanted to get 36 ounces you had to buy 2 16
ounce sodas. He wasn't banning soda. He was just making it harder to
get those large quantities. Anyway, the point is that we need to have
a more informed debate about it. And I think where that debate really
is probably most obvious is for children, because children really can't
make rational decisions on their own. We long ago agreed we have to
make decisions on their behalf.
So nobody debates anymore that we should require seatbelts for children
or require them to go to school or require immunizations. Maybe
there's a few people who debate immunizations but they shouldn't. So
what about physical activity? In Massachusetts, where I'm from, I can
tell you it's a miserable state in terms of physical activity.
American College of Sports and Surgeon General agree children need
about an hour of vigorous activity every day to have a healthy body.
How many schools give the kids hour of physical activity a day. View
it as a trade off. They don't have enough physical activity because
they need this time to study for their exams. But it's a false
trade-off, because physical education actually improves mental health
as well. We're doing our children a terrible, unconscionable
disservice by not requiring more rigorous and vigorous activity in
schools. And we also have bans and coercion. Who disagrees that
children should be banned from smoking or drinking. So if that's the
case, how is junk food any different. Maybe we should ban junk food
from schools as well. I hope that ten years from now we look back on
this debate and think, oh, yeah, the junk food tax and physical
education laws, those were no -- they were enacted in the second
generation's decade of the 2000s. No brainers like we think about
seatbelts and smoking. The bottom line is that we're not going to get
out of this problem without thinking about evolution. Evolution still
matters. It helps explains why we are the way we are. It explains why
we get sick and I also think it helps us evaluate the opportunities
available to us to make the human body better off in the future. And
so with that, I'd like to thank you very much and answer any questions.
[applause]
>>: In your research how much of a role has culture played into all
these environmental challenges. Is that a difference between the
eastern culture and what is acceptable, what's not acceptable behavior,
does that play a role in choices you have and how healthy you are?
>> Daniel Lieberman: So that's not actually something I work on too
much. So the question is how much do different cultures stress
behaviors that have outcomes on health differently and the answer, of
course, is enormously. And we see the differences in health outcomes
from one culture to another. One interesting thing is how fast
cultures are changing around the planet, as industrialization spreads,
fast foods and processed foods spread and urbanization and
mechanicization spreads, those cultures are changing really rapidly,
much more rapidly than ancient cultural traditions. Most cultures, -what your grandmother taught you and you what is a healthy lifestyle is
universal, I would argue, get enough sleep eat vegetables, get lots of
exercise, no brainers around the world. People know this. But change
is our ability to continue to do these. Yes.
>>: I guess I got confused with the point about genetic diseases. When
my doctor asks me if my father had high blood pressure, that doesn't
mean that we go further, somebody in -- the gene didn't have high blood
pressure. So developing in the genes during the modern times.
>> Daniel Lieberman: So the genes that make people, for example, more
susceptible to things like high blood pressure or diabetes, right,
they're not novel genes. They're ancient genes. But so maybe your
grandfather or your father also had high blood pressure. But if you
went back 30, 40 generations they didn't have high blood pressure but
they had the same genes. So those genes haven't changed. The
environments that interact with those genes that trigger the disease
have changed. And furthermore the genes that may make you susceptible
to high blood pressure are not the genes that may make the person
sitting next to you susceptible to high blood pressure because there's
lots of genes and they tend to all have very small effects. Makes it
very hard to find a gene that causes high blood pressure. There's no
gene that causes high blood pressure and they're not common genes and
not genes of a large effect.
>>: So you said that life expectancy now paleolithic more or less the
same, but the diseases we have now are very different. What were the
causes of death then if you know?
>> Daniel Lieberman: So what caused people to die in the paleolithic,
great question. Infant mortality was high in the paleolithic, from
diarrhea and infectious diseases and things like that. What people
died from in the paleolithic was violence and died from respiratory
diseases and they probably died from accidents. But they didn't die
from diabetes or heart disease. So we've done pretty well in many
respects. But not completely.
>>: So when we were able to reduce those noninfectious diseases, like
the diabetes and the heart, what would we die of?
>> Daniel Lieberman: We'd die of old age. Just think about we know
people -- eventually your body does -- I mean everybody who is very old
gets hypertension. Everybody who is very old does succumb to just slow
cardiovascular problems, et cetera, but we wouldn't be dying -- but
also the other thing that's interesting about people who die, don't die
from these mismatch diseases, they also have, they tend to die more
rapidly. It's called the compression of morbidity, or, rather, what's
happening we call the extension of morbidity. So people today are sick
for longer at the end of their lives. And they go through very, very
long declines. We all know what I'm talking about. But if you look at
people who are very healthy. For example, there's a famous study by a
guy named Jim Freeze, from Stanford, done a number of studies on this,
but he's shown that people who basically exercise and eat a healthy
diet tend to have, tend to become sick later in life, considerably
later in life, and when they do get sick, they get sick for less long.
And then they basically die better deaths, for lack of a better term.
So we're essentially extended morbidity, illness, and made the process
of dying much more, much more costly and much more suffering. Yes.
>>: Slightly [indiscernible] question but to the earlier chat I'm sure
as compared to mammals the rest of the mammals [indiscernible] very
long lives. And so given that a population has extended so much and
essentially we're not talking about extension levels scenario right
now, but what does having a much longer life do for us as a species and
people don't reproduce at 70, 80, on how does ->> Daniel Lieberman: What's the advantages of living longer? There
are many. One of them is actually it's a wonderful hypothesis called
the grandmother effect. So hunter gatherers remember hunter/gatherers
are gathering food every day, a hunter/gatherer mother can't get enough
food to pay for her energetic needs on her own, plus offspring. It's
hard in a day out there in the Kalahari Desert or somewhere else for a
mother to get enough food not only to pay for her own body but her
infant who is nursing and her children, toddlers, et cetera, who are
now post nursing but she still has to feed them. So mothers need help.
They get help from fathers. But also they get help from grandparents.
Grandfathers and grandmothers both provide important surpluses which
help pay for their offspring. And so again only recently that we
stopped the system of life. So grandparents in the paleolithic played
very important roles in their own reproductive success. And today in a
strange way we've kind of inverted that because now grandparents no
longer feed their kids, their grandchildren. I mean, my grandmother
brought me cookies and stuff like that. Those were always great. But
that wasn't necessary. My parents didn't need my grandparents to bring
cookies from New York to keep me alive. And you could actually even
argue that grandparents now because of healthcare costs for the aged
are actually sucking up the resources that could go to their
grandchildren, kind of a macabre thought. You could make a prediction
there's going to be selection against living long today just because of
economic conditions and the cost of healthcare. I'm not -- that's a
facetious argument. I'm not sure if that's really true and I hope it's
not. But so really longevity evolved a long time ago for the purposes
of improving reproduction. Again natural selection really only acts
when it benefits how many offspring you have who then survive to have
offspring. Yes.
>>: You mentioned the effect of reading myopia. Now we must have some
statistic on eyeglasses for a very long time now and of course we know
about Gutenberg who got books cheap so mortals could read them without
going bankrupt, the printing spread around Europe like wildfire.
>> Daniel Lieberman: When printing spread myopia increased but it was
just among the educated. When Gutenberg was printing his bibles most
people couldn't read. So as I said before, the evidence is that prior
to the universal literacy it was really only the very wealthy, the very
educated who got myopia. And now it's everywhere, right? Yes.
>>: With all this knowledge and insight, what are the things that
you've adopted in your personal life and your maybe family practice to
avoid this problem?
>> Daniel Lieberman: Gosh, so how do I avoid being a hypocrite.
[laughter] well, I mean, I'm no saint. I'm subject to the same
cravings as everybody else but I try to run a lot. I love running. I
try to promote physical activity. I try to force my daughter to be
physically active, and poor thing, and I'm careful about my diet pretty
much like most people or many people. The thing about diet and
exercise is that they're not magic bullets. Eating a healthy diet and
exercising does not guarantee long life. But not exercising and eating
a poor diet certainly increases your risk of being ill and having
increases your risk of morbidity. And we're all susceptible to the
same problems, and I think our trick is to help each other make the
right choices. And so I try to use forms of self-coercion. One of the
reasons I like marathons is not because I love the marathon so much but
because it forces me to exercise. Because if I know I have a race
coming up forces me to get -- I'm from Boston. It's horrible weather
most of the year and I'd rather not get out of bed and do a long run,
but I have a race coming up and I promised some friends I'm going to
meet them and I have to go out there and do the run and I usually enjoy
it afterwards but I don't love it at first it's self-coercion.
>>: How do you force your daughter then?
>> Daniel Lieberman:
[laughter].
I'm not going to answer that on camera.
>> Daniel Lieberman:
Back in the back.
>>: I wonder if other animals suffer from disevolution, like dogs or
cats probably have an easier life than thousands of years ago.
>> Daniel Lieberman: Yeah, well, we're perpetrating -- there's a dog
obesity epidemic going on. Absolutely. Yes?
>>: So I've seen the latest trend in shoes these running shoes that
look like a foot and this minimalist cushion. How does a body who has
been wearing other types of shoes for 40 or 50 years, what's the impact
of now switching to such ->> Daniel Lieberman: Great question. What happens if you've been
wearing conventional shoes for most of your life and all of a sudden
you switch to minimal shoes. The answer is you get injured probably we
think. Unless you do transition carefully. Because to wear minimal
shoe requires more foot strength. Probably requires more calf strength
you can develop that strength but you're not going to get it overnight
if you buy these shoes buy a minimal shoe it comes with warnings saying
don't, transition gradually, transition slowly, build up carefully
don't do it all at once. And I think that's very good advice, because
you can't suddenly just change from one kind of body to the next. And
I think if you do try to use minimal shoes, do so cautiously and
carefully and mindfully and if something hurts don't do it. Pain is an
ancient adaptation to tell you you're doing something wrong. When you
ignore pain, you're ignoring your biology.
>>: Has there been any [indiscernible] on the minimalist running is
better than shoes with big soles and [indiscernible].
>> Daniel Lieberman: So the question is there any evidence that
barefoot running is better for you. I would argue that there never
will be such a study because I don't think barefoot running is
necessarily better for you. I think that what we can learn about
barefoot running, what I think is important about running is how you
run, not what's on your feet. You can run well in conventional shoes.
And you can run poorly when you're barefoot. The advantage of being
barefoot, however, by barefoot I mean actually barefoot, not a minimal
shoe. I hate the term barefoot shoe. It's an oxymoron. Shouldn't be
allowed to be used. Minimal shoe, when you hit the ground, it hurts.
One of the examples of incorporating a little barefoot running into
your running is teach you not to slam into the ground which is probably
not a good idea. But however simply taking off your shoes doesn't make
you a great runner necessarily. I don't know how many read Chris
McDougal's book Born To Run. A lot of people read it and said I'm
going to throw away my shoes, become perfect; everybody will love me.
And I'll suddenly be able to run ultimate marathons. Takes time. And
not everybody can do it. You can still run poorly barefoot. I think
we have a lot to learn about running from barefoot running. But what
matters about with barefoot running just like with other aspects of
evolution teaches how our bodies evolved and so that we can figure out
intelligently how to make decisions about how to use our body. So you
don't have to be barefoot to get the benefits of what we're learning
from barefoot running. I think it's kind of fun and I think people, I
think it's fun to try. Most people are afraid to take their shoes off
and go running, they think they're going to hurt themselves. If you
run barefoot on a hard surface, your body often switches to forefoot
striking, learn to run in a gentle way. Doesn't mean you'll run in a
perfect way. You can still injure yourself you have to be careful.
That's why I'm skeptical of the paleo diet and going back to an old way
of life doesn't necessarily guarantee health. Hunter/gatherer did not
evolve to be healthy. They evolved to be healthy only in so far as it
helped them evolve to have more offspring. We didn't evolve to be
happy either or to be -- we evolved to be anxious and to be nervous and
to be depressed sometimes. These are all adaptations. It's just that
in our world today sometimes they get out of control. And I think we
can learn a lot from biology, about our biology from studying things
like barefoot running or the effects of physical activity, but doesn't
mean we have to just simply analogize our life back to such simple, to
ancient ways of living. Yes.
>>: Are there any scientific proofs of connection between nonorganic
food and the kind of diseases that you have studied?
>> Daniel Lieberman: The question, the relationship between organic
food and disease. I'm not an expert on that. So I'm going to -- I
study bodies, I'm not an expert on that. I wouldn't presume to answer.
>>: One last question.
>> Daniel Lieberman:
One last question.
>>: Continue on Gutenberg [indiscernible] in Europe. But hit the
Jewish population of Europe because it was ready to read. And in 1950
it hit the Jews of the Yemen, but books being ordered and Yemen
immigrating, have you looked at that?
>> Daniel Lieberman: I haven't looked at those. That's a great study
population to look at. Absolutely. Good idea. All right. Thank you
so much.
[applause]