(slow upbeat music) - Okay, so I'm here to talk about the marathon and running, and I'm delighted to see that some of you are planning to run. How many of you are
thinking about maybe running in the future at some point? Okay, good. How many of you, like, there's
no way you'd ever wanna run a marathon at all in your entire lives? Actually, that's the
smallest number of hands that have gone up, but that's good. I'm guessing a lot of people
didn't raise their hands to any of those questions, which is fine. Anyway, so I would like
to start by thinking about the kind of world that we live in and just to remind us
that the 21st century, if you just watch the news, you realize what a
strange world it is today. But as somebody who studies the evolution of the body, I'd like to remind us all that the way in which
we use our bodies today, it's really profoundly abnormal from an evolutionary perspective. So the average American, for example, today watches about five hours of TV. Okay. We all watch that, right? Yeah, exactly. The average American is
about 23 pounds overweight. The average American throws out about a half a pound of
food every single day, which is an extraordinary amount of food. The average American walks less than three miles a day, which is actually about what a chimpanzee walks, by the way. The average American wears shoes. I can see everybody here is wearing shoes, myself included, right? We eat breakfast from a box, which, if you think about it, is a really strange thing. And the average American,
believe it or not, drives 33 miles a day, about 50 kilometers a day. It's an extraordinary amount, that's the actual, the national average. And so, these are all, from an evolutionary perspective, extraordinarily weird things, and yet the average
American also thinks that what the people are going
to be doing on Sunday is also a weird thing, right? Getting out there, starting on the Embarcadero and running 26.2 miles. I gather there are about 26,000 runners this year in total, in the marathon. I guess not all of them
are running the marathon, some of them are running
the half-marathon. And the average runner is gonna burn about 2,800 calories. I don't think any of us in this room have a chance of winning. Maybe I'm misjudging the physiques of the people in the room, but certainly, I have
no chance of winning. And there's going to be a lot of pain, and suffering, and misery, right? There's going to be blisters, and bleeding nipples, and shin splints, and leg cramps, and broken toenails. There's gonna be a lot of misery out there on the course, though a lot of very happy
people when they finish. And people think this is a
very strange thing to do. And one of the questions is, "Why? "Why do people do this?" A lot of people sit in their armchairs, or stand along the side of
the road in the marathon, or just think about it and wonder, "Why are people doing this?" Well, there's a lot of other
interesting "why" questions. For example, it turns out about a million people run a marathon a year. Why do so many people run a marathon? Marathon-running turns out to be one of the largest charitable
activities on the planet today. Do you know the single
biggest charity in the world that happens on a single day is the London Marathon? Raises about $75 million every year, that's the London Marathon. The New York Marathon waist
raises $25-30 million a year, the Boston Marathon, etc. The big city marathons are huge, so runners raise hundreds of
millions of dollars in charity. And by the way, a bunch
of us are raising money for the Leakey Foundation this year. Not hundreds of millions
of dollars, sadly. Runners do all kinds
of other strange things like, for example, those of you running, I guarantee you that you'd
probably be smearing your body with Vaseline and various
other sorts of things. And then, finally, if you go
out and watch the marathon, people will be doing all
kinds of strange stuff. They'll be wearing weird clothes, and then they won't be... I mean, how many of you
like to have dogs, right? None of you have dogs? Not a single person in
this room has a pet dog? Okay, just a few. I guess we're in a very urban environment. Well, I have a dog, but people don't bring their dogs on marathons. How come we bring our dogs in marathons? So to answer these questions, and there are many more, we can come up with
lots of other questions about the marathon, there's sort of two levels
to think about them, and one are proximate explanations. Those are the mechanistic sort
of "how" questions, right? So one proximate explanation for why people might run a marathon is that, well, they've got inspired by that Robert Browning poem and they want to be like Pheidippides. By the way, you know the
story of Pheidippides and how he... It's the battle of Marathon, and he ran from Marathon to Athens, and then back, and then back, and (indistinct) his army and
supposedly died, you know? Actually, Pheidippides, there's no evidence
that Pheidippides died, it was made up by Browning to
make it seem very romantic. So when people say, "Oh yeah, "I wouldn't run a marathon because "after all, Pheidippides died," you can tell them that that's a Victorian invention by Browning. But anyway, that's another story. So one explanation is they
want to be like Pheidippides, it's romantic, etc. Another is that there are
a lot of people out there who are overweight or unhealthy, etc, and their doctor tells them that if they don't start exercising, they're going to die. And they're Type A personalities, so they invest into exercise just what they did to
invest in their careers or whatever that got them
into that physical state in the first place. And then finally, there's a lot of people, incredible number of people, who run marathons because they had a bet. And I'm not sure quite
where the percentage is, but it's actually a very high number. But those are all proximate explanations for why people run long distances. What's important about
evolutionary theory is that evolutionary theory helps us address much larger, ultimate questions, the "why" questions. And there's a very famous expression by Theodosius Dobzhansky, that's this guy over here, that's, of course, Darwin, Darwin never said this, but Dobzhansky wrote a very famous essay, actually, for high school teachers, entitled "Nothing in Biology Makes Sense "Except in the Light of Evolution." And that's, of course, because our bodies weren't engineered, they weren't designed, they evolved. And to understand why
we are the way we are, we need to understand the
evolutionary story behind that. And so, I'd like to talk today about the why we run. And, for me, this journey
started many, many years ago when we were studying how
pigs stabilize their heads, or actually how humans stabilize
their heads while running, and we started doing
some experiments on pigs, and it led to a long
series of experiments, and ultimately, in 2004, a colleague of mine, Dennis Bramble and I, published this paper in
the journal, "Nature," entitled "Born To Run." And our argument was that humans evolved to run long distances, maybe about two million years ago, in order to hunt and to scavenge. And that our ability to run distances, like the marathon, our ability to go out and run
five miles, 10 miles, etc, is actually quite an extraordinary talent as a result of natural selection, and that it's helped
help make us who we are. It's not all that made us who we are, but it's a part of that story. And to tell that story, since I'm told this is
kind of a cool crowd and I shouldn't give too nerdy a talk, I want to do a kind of thought experiment. So let's imagine it's
two million years ago, and we're all completely
naked Homo Erectuses, okay? Maybe that's not a
fantasy you want to have, but anyway, so imagine it's two million years ago, you're somewhere in Africa, and it's kind of hot and dry, and you're hungry. And imagine, for example, that you're a female Homo Erectus. So females, for most of
human evolutionary history, were either pregnant or nursing, and nursing takes much more time. So typical, nursing female
Homo Erectus, we can estimate, would have needed about
two-and-a-half thousand calories per day in order to pay for her needs, plus the cost of producing milk. But she's also probably got
some kids in tow, right? She's probably taking care of a toddler or some other infants, so she needs, actually, more energy. So she needs a lot of energy, well more than 2,500 calories a day to pay for her basic energetic needs, plus the needs of her offspring. That's a lot of energy, right? Where do you get that kind of food? 'Cause they're living in
habitats like this, right? If you look out here, in this typical African Savannah scene, what is there to eat? - [Audience Member] Zebra.
- Right. It's the zebra, right? So we know that right starting around... Well, the oldest evidence that's secure is around 2.6 million years ago, though, of course, it probably started a little bit earlier than that, but by at least 2.6 million years ago, we have really incontrovertible evidence that humans are... Early humans, our ancestors, Homo Erectus or the
ancestors of Homo Erectus, are eating meat. They're making stone tools. Here, for example, as a
bone that's been cut open, the marrow has been extracted, there are cut marks on it; They're eating animals, right? And that raises a really
interesting question, right? So imagine you're going to try to get one of those zebras, the problem is we have none
of the natural adaptations that other carnivores have to get these animals, right? Usain Bolt is the
fastest guy on the planet at the moment, right? He can run 10.4 meters a second for about 10 seconds. He can run a little bit slower for 20 seconds. He can't run at that speed for much longer than 20 or 30 seconds. He completely runs out of gas. The average... So he's the fastest guy in the planet. The average quadruped out
in the Savannah can run about 20 meters a second, so twice as fast as Usain Bolt, for about four minutes. Usain Bolt would have
no chance of catching any of these animals out
there on the Savannah, right? And probably, this early Homo Erectus
didn't have the fancy training and the shoes, and all the other... The goo and the (indistinct), and the steroids, and
whatever that helped... I'm not saying that Usain
Bolt takes steroids. The Russians, another story, but anyway, okay. So Usain Bolt is not fast enough to catch these animals. The other thing is that humans lack any of the natural weapons of carnivores. We don't have claws, we don't have fangs, we don't have all that fur to protect us because, of course, to be a carnivore, not only do you have to be mean and nasty when you try to kill something, but you also have to deal with the other carnivores who try to kill you. And we didn't have, also, any technology. We often think about, when
we hunt, we use technology, but the bow and arrow was invented less than a 100,000 years ago. The spear thrower, way less than that, maybe 20,000 years ago. Just putting a sharpened
point on the end of a stick, the oldest points that we have in the archeological record
are about 500,000 years old. So for millions of years, for maybe two million years, the most lethal weapons right available to our ancestors were pointed sticks. And I can guarantee you, if any of you go on safari, don't just take a pointed stick and go to try to kill the wildebeest, it's not going to work. The
only way to kill it is you have to get up close and
personal to the wildebeest, which, of course, makes you very much at danger of being... Well, I mean, I just can't
imagine people hunted that way. This would be... You're much better off being a vegetarian than trying to do that. This is a serious fitness-reducing event. The people who make these
illustrations, they look great, they're complete, utter fantasy. Nope, nobody hunts like that. That's really dangerous. So how did we do it? And our hypothesis is that
for millions of years, before the invention of technology, before all the things that we... Star Market or Whole
Foods or whatever it is you shop out here, what we did was endurance running, and we have evidence from skeletons. So this is a very
skeleton of a Homo Erectus that's 1.6 million years old. It's a beautiful skeleton, but we have other bits and pieces. But this is a beautiful,
fairly large skeleton. And I'm not gonna go
into all these details, but we have evidence
from the fossil record for all kinds of features that we see in the fossil record, some of which would have made this species really good at walking long distances, but a lot of these
features have no relevance to walking whatsoever, biomechanically, and they're adaptations for running, and that's really another lecture. I'm not going to go into those features. And so, we can make the hypothesis that we started running
about two million years ago, and here's how it works. So we are able to run
distances, long distances, at speed that make other
animals have to gallop. So to show you this, this is speed on the X axis, and I've plotted it in
the nerdy, scientific way, in meters per second. But here, I've just put... As a marker here, I put for six meters per
second is 21 kilometers an hour or 4.5 minutes per mile. And I plotted, here, the
human endurance running range. So this is the speed up to
which humans can run a marathon. So the fastest runners
on Sunday will be running pretty much close to here. Most of us will be running over in this speed range here. And here, I've got the
trot-gallop transition for dogs, ponies, and horses. And by the way, I've
got a really big dogs. I've got dogs the size of humans, these are greyhounds, right? And the important point is, of course, these animals can go away
faster than humans, right? Usain Bolt's here at
10.4 meters per second, the fastest human on the planet, but the important point is that although all of these
animals can run way faster than any of us can run, we can run marathons at distances that are above the trot-gallop transition of all these animals, and trotting is the
endurance gait of quadrupeds. Quadrupeds cannot gallop long distances. They break down, they overheat, there's all kinds of
problems that they encounter. So even I am a middle-aged
professor, right? I'm obviously not gonna win
anything ever in my entire life. I have never won anything
in my entire life, but I can run faster than
a dog can run at a trot. So I can run above the
trot-gallop transition speed. I can run a marathon above the
trot-gallop transition speed of a greyhound. I can actually run like a half-marathon above the trot-gallop
transition speed of a pony and, again, I'm never going
to win any race in my life, I'm not a great runner. And any decent runner
can easily run above, not on the trot-gallop
transition speed of ponies, they can actually run above the
trot-gallop transition speed of full-sized horses
for marathon distances. And why is that important? Well, because when humans run, we cool by sweating. So this lady at the Westminster dog show, looking rather elegant, if you ask me, she is running with her... I don't know, that's a very
scary-looking wolfhound or something. I don't know, anyway, she's of course burning a lot of fuel and she's generating a lot of heat, but she's sweating. This animal can't sweat. It doesn't have any sweat glands. It's cooling by panting. Short, shallow breaths, which cause evaporation in the oral tract, which cause heat loss, and that cools the
blood in the oral track, which cools the body. Now, the cool thing about quadrupeds, or the uncool thing about quadrupeds, if you're a quadruped, is that when you're galloping, you can't pant, because a gallop is a seesaw gait. And actually, really interesting
experiment that were done when I was a graduate student, in the lab next to me,
when I was at Harvard, showed that as quadrupeds gallop, because of that seesaw gait, their guts slam at the same frequency as their stride frequency, and slam into the diaphragm, so they can't actually
have these short, little, shallow breaths in between
their normal breathing. So they have to train their breathing to their stride frequency as soon as they start galloping. And if you don't believe me,
take your family dog for a run, and you'll notice that
the dog will be panting. Well, it's so cool here, they probably won't
have to pant that much. But on a hot day, your
dog will pant, right? And if you run fast and
you make your dog gallop, the dog won't be able to pant. And when it wants to cool down, it'll do all kinds of devious
things, like my dog does. It'll wrap itself around your legs and just have all these needs to pee, etc, that enables the animal
to pant and to cool down. So if you combine the fact
that we can run long distances that make animals gallop, and that animals can't cool down when they gallop, that gives us a huge advantage, and that advantage is manifested in a kind of hunting called
"persistence hunting." People still do this
today, very rarely though. But what you do is on a really hot day, the hotter, the better, you pick an animal and you pick the biggest
animal as you can, because bigger things get hot faster, just like bigger humans get hot, faster, and you chase the animal, and you try to chase it above it's trot-gallop transition speed. So you make it runaway, and of course it starts heating up. Now, it's going to run
faster than you can chase it and it's going to go hide in the bushes, and then you track it. And, of course, you track it at a walk and then you chase it again. And if you can get to it
before it's cooled down and chase it again, and you've kind of a walking, running, chasing, tracking kind of combination, you can eventually drive that animal into a state of hyperthermia, heatstroke, and you can walk right up to it and you can kill it
without any technology. This guy is using a spear. But in some parts of the world, like, for example, the Tarahumara, where I've been doing research recently, they traditionally just use a rock. They don't bother bringing a spear, they just... Because you don't need any technology to kill the animal at that point, it's dying already, it's defenseless. You can walk right up to
it, if you won't kick you, it won't gash you with its
horns or anything like that. So it's actually not that
difficult thing to do. They're not running that fast. They're actually running
at a very leisurely, kind of, 10 minute mile pace, generally. They're actually walking half the time. They're not running
full marathon distances, they're running more like half marathons. It's not that challenging. The hardest thing about
it is not the running. When you talk to these hunters, they always say the hardest
thing about it is the tracking, trying to follow the animal's trail, trying to figure out
where the animal is going. That's called "persistence hunting," and we have ethnographic
evidence that it occurred all over the world. It was very common here in North America, here in India. In California, for example, there's lots of data from pretty much every Native American tribe was involved in persistence hunting. It also happened all
the way through Maine, like the Penobscot. It happened all the way
through South America, we know it happens in Africa, we know what happens in Australia. We know what happened in the summer even, in places like Siberia. We have evidence that, until recently, this was a very common way of hunting. And in fact, it's still described like... Any of you read Robinson Crusoe, right? He actually runs down
a goat on the island, if any of you know that book, through persistence hunting. So those of you who are running on Sunday, if you're feeling a little bit tired, it's maybe, I don't know, halfway through the marathon. You're like, "How am I
going to make it right?" And you're kind of feeling... Just think about that
animal that you're chasing, and, of course, here in
the San Francisco Marathon, they provided us with bison at the halfway point, and I think it's very symbolic of the kinds of animals
that we might've hunted. So unfortunately, I
think, we're not allowed to chase the bison and it will not be good for
your time in the marathon. So just think about chasing the bison, nothing more than that. So that raises a bunch of questions. And so, one question is, "Just
how good are we at running?" As I already told you before, Usain Bolt would have no
chance in terms of beating any dog or, for that matter, most sheep or goat or whatever. Just how good are we? So we're obviously not
very good at running fast, but what about distance? So it turns out that
there are very few animals that run long distances, and they tend to be social carnivores. So hunting dogs, hyenas, horse, will naturally run long distances. Horses will run long
distances if you force them, if you put somebody on their back or whip them or something like that. At a gallop, they can
go about 20 kilometers. And dogs and horses can, at a trot, be forced to do horribly long distances. There are actually very
disturbing experiments that were done in the 1930s, where they ran animals,
basically, until their death, to find out how far they could go. That's 1930s, fortunately,
nobody does that anymore. But humans, a lot of people out there
training for a marathon will easily run 10 to 15 kilometers a day, which is pretty much what
social carnivores do. And on Sunday, 26,000 people here in the city
are gonna run 42 kilometers. And there are lots of people who like to run ultra-marathons. So humans actually are
able to run distances that match those of the
world's best runners, the animal kingdom's very best runners. And remember, we're not carnivores, right? We're not quadrupeds, we're not horses. We're actually primates. And if you look at what other primates do, it's no contest. Chimpanzees will run about 100 meters and that's about it. Patas monkeys, the other... No, it's true, they're just like... If you watch a chimpanzee run, after about 100 meters, it is a very unhappy chimpanzee. It gets hot and sweaty, and just looking miserable, and it just collapses. Patas monkeys will run, but again, they won't run more than about 100 meters. So we are bizarre compared
to other primates, we're quite remarkable. We're also capable of running in contexts that no other animal will run, right? So we not only run long distances, but we're also capable of
running it in the heat. We have all these remarkable adaptations to run when it's really hot out there. And I can tell you, the last few weeks in
New England have been really, really hot. And we do that because we have
special adaptations, right? We dump heat by breathing
through our mouths. Of course, we sweat. We basically have sweat
glands all over our bodies and we've lost our fur. And you can lose a lot
of heat by sweating. You lose a 581 calories per milliliter, that's a huge amount of energy, or 581 kilocalories per liter. You're losing a huge amount
of energy by sweating, which cools your body. And other animals that run
long distances can't do it in the heat. So if you watch, for example hyenas, or hunting dogs, or wolves, or those Alaskan dogs, etc, I was in Greenland in
March, watching dogs, they only can do this kind of running when it's really cold, they can not do it in the heat. So these animals run... In Africa, they run either at night, or at dawn or dusk. Wolves and sled dogs run in the winter. We can run... We're the only animal
that can run in the heat. As I said before, just to remind you, we can run an incredible range of speeds. So humans can run well
above the endurance speed of other animals. We're actually pretty efficient. When I was a student, there was a study which showed that humans were really
inefficient runners, It turns out that study
was based on one Italian who turned out to be
not a very good runner. The study was redone, fortunately, and corrected for body mass. This is actually a graph
of how much energy it takes to move per kilo per meter against the body mass for a whole bunch of birds and mammals. This is the average line here for mammals, and you can see humans are just a little bit above the line, not any different from horses and various other animals that
are really good at running. We're actually quite efficient at running. And finally, we're remarkable in terms of how long we can run really well. Those of you who have ever
run the Boston Marathon... Anybody who run the Boston Marathon? Yay, okay. So then you know about Johnny Kelley, he was the great Boston runner. He ran every year for almost all his life, from when he was 22 years old up until he was in his 60s or 70s, and you can see that he won several times. By the way, he was the runner
who lost the famous year that Heartbreak Hill got
his name, "Heartbreak Hill," 'cause his heart was broken by Tarzan Brown, who passed him. But you can see that
his best time was 2.14, but he stayed within 20% of his peak time up until his 50s. That's remarkable. And he was still able to
run sub three hour marathons up until he was 60 years old. So humans are not only
able to run really fast, but we're able to run for
a long period of time. If you go out into marathons, you'll see a lot of old
people, or elderly people. I shouldn't say old people, pardon me. I'm hoping to be one of those too soon who are able to run. I've seen 90 year olds running marathons. And finally, to really put
our money where our mouth is, every year, there are races between humans and horses. The first one was started in Wales. You can imagine some drunk guys in a pub, making a bet as to whether or
not humans could beat a horse. And every year, they've been running these man versus horse races in Wales, they're 25 miles. And to be honest, to be fair, most of the years, the
horses beat the men, but every time it's hot, the humans win. And by the way, these are
not elite human runners. These are kind of drunken Welshmen. A better race to look at, actually, is in Prescott, Arizona, where every year, they have
a man versus horse race. There's a 25 mile race, but a 50 mile race. In the 50 mile race, the humans almost always beat the horses. And again, it's only on very cool years that the horses have a chance of beating the humans. And by the way, the horses are required to have veterinary checkups, because they're really
worried about the horses. There are no doctor
checkups for the humans. So humans actually can not only match but often exceed the world's best runners, which are horses. So let's just think,
explore, finally this idea about how important human running is, because I think it helps explain a lot of really interesting things that we're going to see on Sunday. For example, one thing
I've already explained is why we're not going to
see any dogs, right? We'll go out to the
marathon on Sunday morning, you'll see lots and lots of humans, but nobody's bringing their dog and I didn't see, in the race information, any prohibition about
bringing your dog with you. There was no rule that no dogs allowed. But the reason for that is that it would be really bad for your dog, you would basically kill it, right? It would not be good for your dog, unless it was really, really, really cold, and it's not going to be cold enough, your dog would overheat while
you tried to run the marathon. Another interesting question is when you go out and you see runners, occasionally, we do see runners all alone, but a lot of running is
actually very social. Anybody who runs a lot knows that it's actually a very social thing. A lot of us run in groups, we find friends, buddies, and etc. We train in groups and
we run a lot together. And this idea of that running as being a very solitary thing, I think, is extremely modern, and, I would say, a rather
bizarre way of running. And I would argue that this
is actually extremely ancient. Millions of years ago, when people went running and
went to run down an animal, they would not run on their own, they would run in groups,
because you'd go in a group, you'd help help each other, and, of course, you need
a number of individuals to bring that animal back. All the evidence we have
for persistence hunting from every single society was done not by lone individuals, it was always done by groups of people. And I think that that
legacy persists today, that we still run in groups, and we're probably still... When we run, we're still gossiping, the way people were probably gossiping two million years ago. And I think it also helps explain why it is that running and runners raise so much money for charity, right? As I said before, something like, there are more than... Hundreds of millions of
dollars are raised every year by marathoners for charity. And I would argue, this is
a kind of a transference because back in the
Stone Age, when we ran, we ran in order to help each other. We ran to hunt, to bring back animals, which we would share,
not just with our family, but with everybody in the group. We ran, literally, to help each other, and I think that that
instinct hasn't gone away. We still run to help each other, except we no longer... We're not allowed to even kill
the bison along the course, and nobody wants to run down
animals very much anymore, but we still have that
instinct, I believe, in order to run to help each other. If any of you get a chance
to go to the finish line, you'll see some tired people, but you'll see mostly, really,
really, really happy people. And they're not just simply happy because they're not running anymore, although that is part of it. They're actually feeling really good. And most of the people
who do run long distances, once you get in shape and you learn the skill of running, it's quite remarkable how good it is. If you're ever... Sometimes, many of you
may have had this feeling, but you go out for a run, and maybe you were seven
or eight miles in your run, and all of a sudden you realize, "I just feel awesome, I feel so good." It's an effortless thing. Your body is just flowing. And that phenomenon occurs partly because we actually have a
huge number of adaptations that make us so good at it, right? We have all these features
that make us superb runners. Shoulders that are low and wide, and decoupled from our heads, short arms, really big gluteus maximus, which, by the way, as a running muscle, it has nothing to do with walking. Long tendons in our Achilles, and no fur, and our muscle fiber types, and short toes, and
the arches in our feet, and head balancing systems. We are filled with adaptations that actually give us the capability of running really well. And I think that helps give
us this enormous sense... But there are also other adaptations which are chemical, right? How many have you ever
had a runner's high? It's great. The best thing about a runner's high is that not only do you produce
lots of endocannabinoids, the same thing as from pot, but you also up-regulate when
you're running the receptors. (stammering) You're producing the chemical but you're also enhancing
the number of receptors that the chemical binds to, and anybody who's had a
good runner's high knows that it's way better than
anything you can smoke. And we have evidence that
that system evolved in humans, and is present in animals
that do a lot of running and not present in animals
that don't do running. So I think the runner's high, which, by the way, endocannabinoids help
improve sensory perception, maybe an adaptation for us, for when we were tracking and hunting, to improve our ability to
monitor the world around us and see all those tracks, and create mental maps, and figure out what we were
doing when we were running. Why does running make people so healthy? This is one of my favorite studies. There are many, many, many studies on the effects of exercise on health, but this is a local study, it's just from down the street, so I thought I'd show it today, and it's just on runners, and we're talking about running today. But this is the famous
Stanford Runners Study started by Jim Fries in the 1980s. He took 538 runners, these were not elite runners
and marathoners, etc, but members of the Stanford/Palo
Alto/whatever running club, and he's been following them ever since, and compared them to a
group of matched controls. These were not overweight people, they were not smokers, they were not drinkers. And he's been studying them ever since, and looking at how their
health has progressed, and not only measuring mortality, but also disability and morbidity. And you can see that, this is from 2004, so this
is 25 years into the study, that the runners, 20 years later, had 20% lower mortality rates than the non-runners. It's a huge difference, right? And the runners had bodies
that were, on average, based on these disability measures, that were 14 years younger. They were basically aging at half the rate as the non-runners. And that, of course, there's a lot of interesting
biology behind that, but it's not that running, I would say, or physical activity, is a medicine that makes you healthy. I would argue it's the reverse, that the absence of physical activity is what makes people unhealthy, and we sometimes get that wrong. Our evolutionary history
runners also explains why we can do it in barefoot, but that's another lecture. But here's Abebe Bikila
who set the world record in the Rome Olympics in 1960, barefoot. This is Ken Bob Saxton, we
were talking about him earlier, running the San Francisco Marathon. I dunno how many marathons
he's run barefoot. You can see he's wearing a beanie hat, so yes, he is a little bit odd. Lots of other people run
barefoot, you can do it. There's been a lot of hullabaloo about it, but it's not actually that big a deal. And finally, I think that
running can help us understand some human universals. I don't know if you know
about human universals, but there's been a lot
of efforts over the years to try to figure out what's common to all societies, right? So for example, all
societies cook their food, we all have marriage, we all have mother-in-law jokes, we all have music. But it turns out that
one human universal is that every culture in
the world has underwear. We all have some form of
modesty accoutrements, right? And there's lots of different kinds, and some of them are more
interesting than others, but I would argue that maybe this also has something
to do with running, because when you run, you're creating substantial accelerations of your body, right? Running is actually jumping
from one leg to another. That's basically what you're doing when you're running, biomechanically. And, of course, when you jump, you're accelerating your
center of mass up, right? And then, as you fall, your center of mass is
accelerating downward, and you're going up and down, and up and down, and up and down, right? And all of you remember
high school physics, right? Remember Newton's second law? For every action, there's an equal opposite reaction, right? So when this guy's body
is accelerating downward, everything that's not tied
down is going to accelerate up. And when he's accelerating up, everything that's not
tied down, like his penis, is going to accelerate down. It happens with breasts too, right? Anything that's not tied down. And so, I would argue that when we started running
millions of years ago, and we have to run really long distances, all that jiggling and flapping was perhaps a little bit uncomfortable. And so, we figured out
how to tie things down. By the way, this is the
oldest known underwear that's found from the
archeological record. It's from an Egyptian tomb. So the benefit of underwear is that it prevents some of
that annoying jiggling. You can think about that
on Sunday when you run, or when you watch the runners. But, of course, everything has trade offs. There are costs and
benefits to everything, and that the benefit may be less jiggling, the cost, of course, is chafing. And so, you'll also see
some things like this too on Sunday as well. So in short, I would like to argue that everything, nothing in biology, including
jiggling penises and whatever, but nothing in biology,
including the marathon, makes sense except in
the light of evolution, and that running is part
of what made us human, and that on Sunday, when we
watch all those folks out there, and those of you who are running, I hope you have a great time running, that what we're not doing is
anything strange or weird... Well, I mean, it's a little
bit strange and weird, 'cause nobody ever got on the line and ran 26.2 miles without
stopping to another line. But beyond that, the basic act of running and the reason that we run
actually hasn't changed all that much for over two million years. So for those who are
running, good luck on Sunday. Thanks, and thanks to
the Leakey Foundation, and I look forward to
taking some questions. (audience applauding) So it's quiz time. All right, I'm a professor, so it's... I don't normally do true and false, or multiple choice questions, but you're going to get some
multiple choice questions. Okay, so here we go. Everybody ready? How much more efficient are
men than women at running? Hey, zero... You can read it yourself. Zero, five, or 10. So you know what efficiency is, right? Efficiency is how much... It's like miles per gallon. How much energy use per
unit mass per unit distance. - [Audience Member] How are
you measuring efficiency? - That's what I'm just saying. How much energy you use per
unit mass per unit distance. So the answer is actually
zero percent, correct. It's an old myth. So women aren't as fast
as men on average, right? Although, there are plenty of women who are a lot faster than a lot of men. But actually, that old myth that wider hips make
wake women less efficient at running or walking
is completely untrue. And interestingly, if you
go back in literature, the first equipment ever used to measure oxygen
consumption during exercise back from the 1920s, something called a "Douglas Bag," actually, even back in the 1920s, we knew that women were no
less efficient than men, and yet this idea has
pervaded our psyche for years. Yeah? Oh, it's very common. In fact, there's something
called "The Obstetric Dilemma." People argue that that women... Why don't women have wider hips, right? To give birth to bigger babies. And the argument has always been... The argument that they
don't have wider hips because if they had wider hips, it would cost them more for locomotion, and therefore they couldn't have wider... So therefore, women have
problems giving birth to babies in order to save energy
in order for locomotion and there's a trade off. It turns out that wider hips don't actually cause women to become
more costly in locomotion, which raises an interesting question, which is why, still, don't
they have wider hips? But it's not because of locomotion. And one possibility is that
actually, until recently, women didn't have such
problems giving birth, that the obstetrics were less complicated until we started getting
really, really big babies. But that's another lecture. Okay, back to que... So question number two. "What is the most economical
speed for a trained runner? "Seven minutes a mile, "eight minutes a mile, "nine minutes a mile, "or they cost the same?" The answer actually is A, so one of the...
(audience laughing) I had nothing to do with the... So it turns out that one of the really interesting
things about running for most animals, the cost of locomotion, so how much energy it costs to run, if you graph speed on the X-axis and cost on the Y-axis, it's a U-shaped curve, just like for walking. So there's an optimal
speed for walking, right? We all know that there's a
speed at which it's best to walk and if you walk slower or faster, you're spending more energy. And most animals, when they run, also have a U shaped curve
during running, right? There's a... Ponies and dogs, there's
a speed that they're best, most efficient at. But one of the fascinating things about humans is that if you
run from here to Berkeley, I guess there's a Bay in
the way, but whatever, if you run from here to somewhere at a six minute mile,
or a seven minute mile, or an eight minute mile, it'll cost you the same
amount of energy to get there. And that's because humans
have what we call a "flat cost of transport." And does anybody know why we have a flat cost of transport? Actually, as a hint, let me guess here, can you think of any other animal that might also have a
flat cost of transport instead of a U-shaped? - [Audience Member] Kangaroos.
- Kangaroos, yes, absolutely. It's because humans have
incredible springs in our legs. So when we hit the ground, we store up all this elastic energy in our achilles tendon
and various other springs, and also also our feet, and we get that energy back. And the faster you run,
the harder you hit, but the more energy you save, and then it gets returned to you. And so, human running is
remarkable in that it has... It's cost is speed independent up until you start sprinting. When you start sprinting, then it gets more expensive again. Because when you're sprinting, you actually start increasing
your stride frequency, and then you have to expend more energy to accelerate and decelerate your leg. So that's one of the cool
things about running. And one of the things that makes the skill of running interesting is that you can actually speed up and not... So when people are running
the marathon on Sunday, the folks who win the marathon or coming in just a little over two hours, they're not spending any more
energy to run the marathon than the people who take
four hours or five hours. They're actually expanding
the same amount of energy, they're just running better. All right, next question. "How many miles a week does "an average Tarahumara runner run?" So maybe you read the book, "Born To Run," popularized a lot of my research. The Tarahumara are these
famous runners from Mexico, from the Sierra Tarahumara, and they're famous long distance runners. So zero, 20, 40, and 60. We've collected data on this, by the way, so I actually know the answer. Oh, this looks like the 60s have it. How many of you voted zero? You're correct. They don't train. They don't even h... Well, actually, if you
want to ask the question, "How many miles did they actually run?" It would also still be zero. People there don't run
unless they have to. That's actually one of
the things that's wrong about the book "Born To Run." "Born To Run" makes you think that everybody there is
running all the time. They only run when they need to, usually when they have
races or ceremonies, but most of the time, they walk. Running is not something that people do, except on a rare occasion. It's actually one of the
grievous errors of that book. Okay, is there one more
question or is that it? Oh, yes. Last question. "Which generates more impact," collisional force when you hit the ground, "when you land on your heel, "what we call a rearfoot
strike or heel strike, "when you land midfoot, "with the front and the back "of your foot hitting at the same time, "or land on the ball of your foot, "or D, it depends on the shoe?" Yeah, it is incorrect. Rear foot strike is correct answer. All right. So what... And just (murmurs) explain, but basically the biomechanics is that when you land on your heel, there's a lot of collisional
energy exchanged, and it's exchange of momentum. So momentum is mass times velocity, right? And it has to be conserved. Remember of conservation of momentum? So when you land on your heel, pretty much your whole body
from your knee down stops at a certain, and it stops pretty rapidly. And there's what we call an impact peak. You can hear it right when
you hit the treadmill, there's a thud, right? But when you land on
the ball of your foot, only your foot has stopped. Your ankle is still coming down, your knee is still flexing. So much less of your body stops, and you also land at a much more, what we call, compliant
or less stiff position. So if I got you all to jump up now, you're welcome to do that, by the way, you'll all land on the
ball of your foot, right? And you land quietly, right? If you were to land on your
heel, which I do not recommend, you'd make a lot more noise and you'd also hurt yourself. And that's because you're
using all those joints in your body to dampen
the forces when you land, and less mass is actually
involved in that collision in the first place. So running is jumping
from one leg to another, and when people are barefoot, it hurts to land on their heels. So most people, when they're barefoot, don't land on their heel, they land on the ball on their foot. And it's really the modern running shoe that allows people to land on their heel, and there's a huge debate about whether or not that is good or bad, and all that sort of other stuff. But that's another story. Okay. So what we're going to
do now is transition now to talk about running form, because one of the things that I think is important
about running is that, although it's something
that we have been doing for millions of years, I also believe that, like also many of the things we've been doing for millions
of years, like throwing, it's a skill. And that we have this idea in our culture, that all you need to do is
give somebody a pair of shoes and send them out running. And first of all, everybody can run, just
like everybody can walk, but the more I study running in different parts of the world, and I've studied it in almost
every continent in the world, and the more I talk to runners, indigenous runners, people who learned to run in various cultures, the more I hear from runners
that they think it's a skill, it's something that you need to learn. And just like many skills, we learn by watching and imitating people who are really good at it.
So in Kenya, for example, Kenyan runners will actually
take turns being the leader, and then they'll follow and imitate the person in the front of the pack. Tarahumara do the same thing. Running is, as I said
before, a social thing, but also a skill. And so, one of the debates
that's really going on now is, "What's the best way to run?" And so, as a way of discussing that, and as we thought it would be fun to, to get two people up here and running, and what we'll do is we'll get some on the treadmill, and we'll film them with the iPhone in slow motion, project they're running on the screen and we'll talk about their running form. So let's start with our first victim. (audience applauding) What's your name? What's your name? - My name is Kathleen. - Kathleen, all right. So before we start, how much do you run? - The last week, just twice, but whenever I can.
- Okay, good. All right, so Ian will measure Kathleen and we'll get her up to moderate speed. And obviously... You know, normally, in the lab, we get somebody running for
a good five, 10 minutes, to get them warmed up
before we measure them. - All the whispers don't help. - You're doing great, you're doing great. 26.2 miles, absolutely. - It's only 11... (indistinct) like 11:30? - 5.2 miles per hour. All right, are... Ian, what do you... Are we good? Should we put Kathleen
out of her misery here? All right, excellent. All right. So while you get that loaded, so there's obviously
a lot to running form, but I would say that if
you were to sort of poll... So I'm going to give what I
would say is a consensus view rather than my own peculiar view, okay? So if you were to pull a lot of people who study running and ask them, what are the key elements of running form that really matter in
terms of performance, but also possibly injury? I think most people would agree on four components of running. The first is posture, especially how much you lean from the hip versus from the ankle. So everybody, when they run, you lean a little bit forward, but you see a lot of runners out there and what they're doing is when they lean, they lean at their hips, right? You all see that person
running like that, right? When you do that, that actually creates big bending moments around your hip, right? There's a torque, 'cause you think your... Your upper body is sort of
separate from your lower body and it has a high center of mass. Every time you hit the ground, it wants to fall forward, and that's a high amount
of angular momentum, right? The mass... If any of you remember the mass moment of inertia from high
school physics, right? There was a lot of mass
that's positioned very high up and it's being accelerated
around a axis around the hip, and that's creating a lot of force, and you have to then counteract that with your butt and your back. So leading a lot from your
hip is actually a problem. So I think good running
form involves good posture, and I think you had pretty good posture. A second component to running form is your stride frequency. So it turns out that... So how many times a minute you step, let's call it your step frequency, turns out to be very important in terms of a number of things, one is economy. So almost all people have
an optimal frequency. So I told you there's no optimal speed, but there is an optimal
frequency for running. And for most people,
it's about 170 to 180. Actually, 172 is the average, according some studies that we've done. There's Kathleen running. So you actually were
running at about 152, 153, so you're actually running inefficiently. And the other thing that happens when you have a very
low stride frequency is that speed is stride rate, or step rate, times step length, right? So when you have a low step rate or a low stride frequency, that means you have to
take really long steps. When you take really long steps, that means you have to
land with a very stiff leg, and that puts a lots of
forces around your knee, what we call high moments. So if I were you, one of the things I would do is I would increase your stride frequency, and get up to maybe about 170. Well, that takes a little bit of practice. The third component of running is... We were going to do posture, stride frequency, foot strike, and... Not yet. And there was one other one
I was going to talk about. Well, anyway, so foot strike is the third one, right? So we already talked about the fact that there's rearfoot strikes, midfoot strikes, and forefoot strikes. And Kathleen is clearly
a forefoot striker. So she's landing on the ball of her foot, which for the kinds of
shoes she's wearing, is exactly what she should be doing because you're wearing a minimal shoe that has no cushioning. And so, that's good. So you're landing on
the ball of your foot, but there's a trade-off. So a lot of people who land... So a forefoot strike, is a very gentle way of landing but if you land that way, you have to have really
strong calf muscles. And what happens is a lot of people, when they switch, for
example, to barefoot running or minimal shoes, they have a hard time doing that because they don't have
the calf muscle strength and they get calf muscle strains. And sometimes, they get problems in their Achilles muscles... Achilles tendon. They got Achilles tendinopathies. But those, you can actually
train yourself through. You can adapt, strengthen your calf, and strengthen your achilles. And then the final thing... Can we pause at the moment of impact? And the final thing I
want to talk about is something called "overstriding." So an overstride is when you land, and where you land with your foot, there's two ways of defining it. One is where you land your
foot relative to your... Is that, is it pausable? Here we go. That's pretty good. Can you advance like one frame? Is that a problem? Oh, that's not too bad. That's a little bit... It's a little bit in, but they don't have the
technology we use in the lab. But everybody lands with their foot in front of their hip, unless you're a world-class sprinter. If you watch your Usain Bolt, when the Usain Bolt lands, his foot is right underneath his hip. And if you think about it, for every action, there's
an equal opposite reaction, so if you land with your foot out here, you're pressing against the
ground in that direction. So the ground is going
to press back against you in this direction. It's going to break you,
it's going to slow you down. Now, if you're trying to
win a 100 meter sprint and the ground is pushing you backward, that's going to slow you down and you're going to lose. So world-class sprinters have to land right underneath their body, so there's no deceleration. That takes enormous strength. You have to have really
strong gluteus muscles and really strong hamstrings, and you just have to be really strong, which, of course, these
great sprinters are. But the problem is that they store up much less elastic energy
when they run that way, so that's not an endurance way of running. Endurance runners have to land out here but one thing that they do do, and Kathleen is pretty good at it, is that when you land, you have to land in front of your body and there is some deceleration
of your center of mass, but we've learned, from various studies, that the best way to land
is with a vertical tibia. So you don't want to land like that, or like that, you want to land like that. So your shank should be vertical. When you do that, you actually produce a lot
less force around your knee, and you store up more energy, and there's less braking force. So I would say that Kathleen
is a pretty darn good runner. (audience applauding) And the only thing that that might improve your economy a little bit is to increase your stride frequency. But beyond that, I'd say you're ready to run the marathon. Good. - [Kathleen] (indistinct) - Good, excellent. Thank you so much.
- Great meeting you. - All right. All right, who's next? - What's your name?
- Amber. - Amber, okay. And one of the cool
things about iPhones is that you can slow down... I mean, if anybody wants
to get a gait analysis, I mean, anybody who has a
decent phone can now do this. Get somebody to film you on a treadmill or when you're running outside, and there's some good websites out there. That's pretty fast. Now, one thing you didn't
notice about Amber, can you notice that she's making a lot more noise than Kathleen did? That's because she's heel striking. She's got more impact. - Do you wanna keep going?
- I think we can stop. All right. (audience applauding) So first thing is, remember we're talking
about four different aspects of running form, right? Posture, cadence, overstride, and strike. So your cadence was totally
different from Kathleen. So yours was about 172, actually. So you're running with
a very high cadence, pretty much close to what
most people predict is the average optimum for most people, so that's good. Perfect cadence. Let's take a look at her posture. It was kind of harder to... It says "pretty good
posture," so excellent. So she's running really well, she's got no really serious
leaning at the hips, which is really good. So that means that she's not losing energy with all that sort of
tilt of her upper body. She's got excellent stride frequency, but you'll notice, if we can freeze it at the moment of impact, Ian, I know this is a little challenging... The one thing... Okay, there, perfect. Okay, so that is a classic heel strike and a classic overstride. See how Amber's tibia, her shank... Hold on, we actually have a... Forgot I have one of these. Her shank is not vertical. Kathleen's shank was very vertical, but hers is angled out there. She's landing pretty hard on her heel, but fortunately, she's got
lots of cushioning in her shoe, which slows the rate of loading. It doesn't actually get rid of the energy, but it just slows the rate of loading of that energy. But we know from a bunch of studies that that kind of landing
generates very high torques around the knee. You have lower torques around the ankle than the way that Kathleen was running, but there's always a trade-off, and that trade-off is in the knee. And some researchers... There's a big debate going on, but some researchers believe
that this kind of landing, if you are doing a lot of running, 15 mile miles a week is not so much, so it's not a big deal, but if you were to go up
to like 50 miles a week and run like this, you might, by some people's arguments, be much more at risk of shin splints and-- - Last year, I broke my fibula. Stress fractured my fibula running. (indistinct) about 50 miles a week. - Okay, well, there you go.
I didn't know any of this. We did not have any
conversation beforehand, but that's typical of
this kind of running form. It's very high impact, and we could all hear that, cause you're running
in a way that really is a very stiff-legged form of locomotion. And if you were to get
your knee up a bit more, by flexing your hip more, and land with a more vertical tibia, you could still... You don't have to necessarily
lose the heel strike. If you want to still be a
heel striker, that's okay. But if you land with a
somewhat flatter foot and a more vertical tibia, you would decrease the amount of force that you hit the ground with, the impact, decrease the amount of
torque around your knee, and that might actually help with that. And I would say of all the things that you're doing in you're running, the overstride and the heel
strike are very linked. So by some people's
arguments about running, and I'd have to say that as a note, nobody agrees on any of this
sort of stuff completely, and so I don't wanna be too prescriptive, but your injury does fit that pattern, which is that you're
overstriding and heel striking. And that can be tough when
you're doing a lot of... When you have a lot of impacts. Other than that, awesome. Good, thank you. (audience applauding) (upbeat music)
