Brains, brawn & the evolution of the human body: Daniel Lieberman at TEDxBermuda

okay so I don't know about you folks but when I was a kid when I was in school everybody as well as I assumed that I was just the biggest nerd in the world nobody ever applied the term athletic to me when I was a kid I guess wasn't fast I wasn't strong I wasn't powerful I wasn't good at making goals I was the proverbial nerd that was big blast for every team and so I did what most nerds do I became a professor and I became a professor human evolutionary biology and one of the reasons of that is that one of the central stories of evolutionary biology is that humans are special not because we're stronger athletic but because we're smarter right we're after all Apes and if you skin a chimpanzee it looks not actually that different than if you would being the big thing that makes us exceptional is that we are extraordinarily large brains so chips are pretty gravy they have brains about twice as large as you expect from them on their body size but human have humans have ginormous brains are great about five times the size to expect from men on more science in addition even the most athletic amongst us are really pathetic right we say mold who's the fastest human being can run about 10 meters a second for about 10 or 20 seconds but a chimpanzee can run twice that speed without any training or drugs and can easily climb trees in a much more agile way that any Acrobat chimpanzees I'm about twice to maybe five times as strong as the strongest human being that much more lethal they have all kinds of natural pretensions of just further etc humans really are pathetic creatures so when it comes to other animals in the animal world so the standard story about human evolution is that we triumphed over nature and do the call because we're smart might we use brains to try to poke a wrong and in fact that idea that myth has actually underlies one of the biggest hoses ever in science the famous cook down public so this was a supposed fossil that was discovered in the South of England it was that actually an orangutan John a human skull all mushed up and made to look old and found in a pet pen and it confirmed what English scientists really wanted to know right what does that give us a course involved in England where else and the other the other is that big brains led the way in human evolution well more than a century of research has proved that that's incorrect right this is a graph of brain size over the last five seven million years and you can see that for the first five or seven million years of human evolution our brains really didn't change in size from those of chimpanzees and it wasn't until about two million years ago that our brain started getting bigger in fact not till about a million years ago that they began to get into the modern human range and that's for a reason brains are really problematic organs just sitting there listening to me you're spending about 20% of your math metabolism to fuel your brain and if you're not even listening to mean asleep you're still spending about 20% of your metabolism to take care of your brain and it requires all sorts of special housing and plumbing to to keep it going and and they take a long time to grow at chimpanzee takes about three years to grow its brain to full size humans take about six to seven years to grow our brain to full size and then we need another 12 years or so to prune those synapses and get the brain working as an adult and brains also complicate the process of birth as many of you in the room no doubt know a human newborn and has a brain the size of an adult chimp and to get that brain through the mother's birth canal means that we have to turn sideways to get into the birth canal and then rotate 90 degrees in order to get out it's a perilous and dangerous and difficult journey so what I'd like to argue today is that human evolution is not a triumph of brains over brawn but actually brawn has been very important in human evolution but a special kind of brawn endurance and that an order us for us become really smart we actually had become endurance athletes and that endurance athleticism is fundamental to human biology and is very important to the future of human health so in order to understand this process we need to turn the clock back many millions of years ago this is a graph of the earth temperature over the last 30 million years and you can see that about 5 to 7 million years ago there was a major cooling of the Earth's climate and in Africa that caused the rainforest to shrink in the woodlands to start expanding and we evolved from creatures that were living in forests they we were Apes and imagine living at the margin of the rainforest and all of a sudden those fruits are less available and they become more seasonal and they you have to travel farther and it's harder to get them and so the first hominids the first creature is more related to us than to chimpanzees it turns out were bipeds they were basically ape-like bipeds and the good thing about being a biped is that it helps you feed upright in trees and maybe helps you feed from the ground and also it makes us much less costly at locomoting chimpanzees and gorillas are local walkers and they spend 4 times as much energy to move as we do and the typical chimp goes about 2 to 3 kilometres a day so for the same amount of energy humans could go 6 to 12 kilometers a day which would have been an enormous benefit when foods are more scarce and harder to find but the problem with being a biped is that as soon as we got up on two feet we became unsteady easy to topple over and we lost the ability to gallop we've become slow ever since then but it wasn't a bad thing for the first few million years of human evolution our ancestors did pretty well there was a big radiation of them they're called australopiths that I'm not going to talk about them there are many species and they they lived in different parts of Africa and they were good at walking and they were good at climbing trees and they probably ate a vegetarian diet for the most part of nuts and fruits etc but the world changed again around 7 million years ago I'm exceeding about about 3 million years ago and it started cooling again and when it did so Africa's climate changed as well and we had a expense an increase in the size of those savannas the big grassland habitats and that would have posed a major challenge to our ancestors who were living there and we see two different responses now one was a group of australopiths we called a robust australopithecine big chewing muscles and they probably spend more than half their day chewing mechanically demanding really low quality food but the other response that occurred the same time was the origins of the human genus the genus Homo and we became high quality food specialists we invented hunting and gathering so what a hunters and gatherers do well they they rely on a number of important technologies they process food with with with tools so the oldest tools are actually about this about 2.6 million years ago hunter-gatherers rely intensely on cooperation and food sharing and division of labour they they range long distances every day so remember chimps go 2 to 3 kilometres a day but hunter-gatherers go 9 to 15 kilometres a day to get the high-quality foods that they need and one of those high-quality foods which is essential important to human biology until very recently it was meat we started eating meat around 2 and 1/2 million years ago and we even have ancient bones that have cut marks and smash marks it's evidence of meat being cut off and marrow being extracted but that raises an interesting problem how did we hunt right we think when we hunt today we think of weapons right we use technology like bows and arrows and guns and and things like that but those technologies were not invented the bow and arrow was invented less than a hundred thousand years ago even putting a sharp stone point on the end of a stick that was invented less than three hundred thousand years ago in fact the both lethal weapons available to our early hunting ancestors was a sharpened wooden stick or a club and I don't think anybody in this room would have wanted to try to kill a wildebeest or a kudu with a sharpened wooden stick you're much better off being a vegetarian we can't chase them either right remember the fastest humans can run about ten meters a second but most of the animals that we hunt can run 20 meters a second for many minutes you can't catch them but we think the answer and we by we I mean my colleagues Dennis Trammell and David carrier think that the answer was our ability to run long distances and let me explain how it works so this is the this is speed on the x-axis and this is the speeds at which humans can run long distances defined as of Marathon here and this is the human sprinting range and I'm comparing that to the trot speed and gallop speeds of animals of who are quadrupeds right so a typical human being like me a mid middle-aged professor right I can run above the chart gallop transition speed of a full-sized dog of a 65 kilo dog fact I can run above the transition speed of a pony and good runners can easily above run above the trot gallop transition speed of a full-sized horse and that's really important because when you make a quadrupedal up you limit how much that animal can run because galloping is not an endurance gait and the reason for that has to do with thermal regulation humans cool by sweating we actually extrude water all over our body use all that surface area to cool the skin and the blood below it but when animals run they pool mostly by panting you know the short little shallow breaths of air going over the tongue in the oral cavity air and that evaporates water in the tongue that cools the tongue that cools the body but it's a much smaller surface area and the other thing is that when an animal gallops its guts start sloshing back and forth like a piston engine slamming into the diaphragm with every stride so as soon as animals quadrupeds start galloping they have to they have to synchronize every step with every breath and they cease to be able to pant and you want to test this hypothesis go take your family dog for a run you'll notice if you make it gallop it won't be able to pan if it's a hot day I'm afraid you might kill the dog so don't do it for very long so we take advantage of this of opportunist this ability to do what's called endurance persistence hunting and it's still practiced in parts of the world such as the Kalahari and hunters a group of hunters will pick an animal usually a big one the bigger the better because bigger animals just like bigger humans overheat faster and they'll make the animal gallop and if you can make the animal gallop it will rush your way into the bushes and then you have to track it and then you chase it and a combination of tracking and chasing running and walking you can get that animal's core body temperature up and up and up until eventually it reaches a state of hyperthermia as this poor kudu is reaching and at that point the hunter after may be running 10 to 25 kilometers can walk up and easily dispatch it with very little technology and no risk for of bodily harm and of course this is pretty rare now because we've invented technologies like the bow and arrow in the supermarket but until recently it was probably very important and we have evidence that people did it all over the world in Africa in the Americas in Australia it was probably how we hunted for millions of years before technology and not surprisingly we see in the fossil record all kinds of features adaptations literally from our heads to our toes that make us really good not only at walking long distances but also at running long distances adaptations like having big butts and special ears is a vestibular systems to sense the pitching motions in our head and when humans begin to become hunter-gatherers and we am good at endurance athleticism and walking long distances and running long distances to hunt and gather that was when we released an energetic constraints on our brains and that's when brain size really started increasing in him and evolution and then further technologies such as fire and other and projectile points which were invented actually pretty recently the last three four hundred thousand years those further made energy available to our ancestors to help us grow big brains so the important point I want you to think about today is that for the last two million years or so we weren't endurance athletes day in day out with no Sabbath no break nothing that's how we made our living to have a female hunter-gatherer walks nine kilometres a day and when she's coming home she's slapping huge quantities of food she's carrying babies she's processing she's digging men will run and walk 15 kilometres a day and we have to dig holes and climb trees and do all kinds of other tasks that involve vigorous activity and that those those performance benefits had amazing benefits for our our lineage as a whole and as soon as we invented hunting and gathering we started colonizing the rest of the old world and we got into the caucuses into Europe and to Asia and the hunting gathering way of life persisted until we invented agriculture starting around 600 generations ago so how is this legacy as endurance athletes as hunter-gatherers relevant to our lives today well many of us are very aware that that we have a crisis now in terms of health in the United States two out of three people are overweight or obese and levels of disease like diabetes and and cancer and osteoporosis and heart disease are are going up at very scary rates and we know that these diseases often come from a combination of eating too much and exercising too little and we spend a lot of time thinking about how much we eat and we spend a little bit less time thinking about how much we exercise when you look in the literature and and it's hard to get good precise numbers for hunter-gatherers but it turns out that hunter-gatherers eat a modest diet late your abnormal amount of calories about 1900 calories a day for females and about 2300 calories a day for males and actually they're not so vigorously active as we sometimes imagine them to be they're active but they're not crazily active right we can measure that with what's called a physical activity level that's the ratio of your metabolism how much energy you're spending relative to the metabolism that you're spending basically when you're asleep and it turns out that hunter-gatherers are pretty active but not not as activists say modern athletes you know who are training for marathons they have physical activity levels of about 1.8 and farmers are about the same for most of human evolutionary history and a lot of people today actually reasonably modest diets they try to watch what they eat ensure some people eat eat you know enormous quantities of food maybe 3,000 calories a day but most of us aren't actually eating that many calories the big thing that's shifted for us is that we no longer have to work physical activity levels from many post-industrial peoples have fallen to really low levels of like 1.3 to 1.5 and you can think about it right you get up in the morning you take your car to work you take the elevator to your office you sit in a desk all day long the biggest work you have to do to get dinner is to reach to the shelf and put that box in the microwave right we don't have to work anymore in order to make a living and we're paying a price so I think that sometimes we demonize the food that we eat a little bit more than we should maybe demonize the machines that we use that make us have to no longer work in order to live from day to day and exercise now has become really a pastime it's become something we do for fun and it's a privilege of the wealthy in many schools we're reducing the amount of exercise that kids have because we don't have time in the day because of all the standardized tests that they have to take for them to get any exercise anymore and we're paying the price very dearly because vigorous exercise is critical for health right we know that when you exercise you make your hearts you cause your peripheral circulatory system to to improve and expand you cause your endocrine system and your digestive system to behave better people who exercise a lot don't get adult onset diabetes it's important for your musculoskeletal system to grow a healthy skeleton and not face osteoporosis the most important thing you can do is actually exercise when you're young and still growing your skeleton and exercise is important for your immune system and for other parts of your body one of my favorite studies because I'm a bit of a runner is the Stanford runners study which was started in 1984 they picked 538 runners members of runners clubs and they compared them to sedentary but healthy controls and they followed them ever since right and more than 20 years later the runners have a 20% lower mortality than the controls and if you measure disability you know the ability to climb stairs and things like that the runners have 50% lower disability scores they have bodies that are on average about 14 years younger this is one of many studies which shows just how important exercise is for human health it's also important for mental health when you exercise vigorously you increase all kinds of neurotransmitters in the brain like norepinephrine and dopamine and serotonin which have important effects on obsession and memory and compulsion and reward and pleasure and alertness a lot of mental health problems today are caused by people not getting enough exercise and there's no drug manufactured that is as effective as in vigorous exercise for curing problems such as depression and anxiety how often when somebody goes to see a psychiatrist for depression are they prescribed exercise not enough it's something that we have to reverse in our society so the great evolutionary biologist theodosius dobzhansky once wrote an essay entitled nothing in biology makes sense except in the light of evolution I hope I've convinced you that endurance exercise is important part of our biological heritage we evolved to be superlative endurance athletes and that endurance athleticism was actually a necessary precursor for us to grow such big brains that gave us culture and technology and all those other things that make being a human really special and that exercise is medicine not as a fluke but because it's part of our evolutionary legacy so all those years ago when I was in high school thinking I was a pathetic wimp and a nerd and not a very good athlete well it turns out I was partly correct I am a nerd there's no question about it but I've discovered as I got gotten older that I'm a flake but I'm not an athlete who's good at speed or power or kicking goals I'm good at running long distances and walking long distances and the reason I'm good at that is because of my evolutionary heritage and I honestly believe that more of if more of us paid attention to our evolutionary roots as athletes that the world would be a far far better place exercise is good for us because it's what we evolved to do thank

Channel: TEDx Talks

Views: 49,362

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Keywords: TedxBermuda, ted talks, ted x, tedx, tedx talks, Evolution, endurance, ted talk, Barefoot running, athletes, tedx talk, Lieberman, Daniel, ted

Id: OtQhybh4zug

Length: 18min 4sec (1084 seconds)

Published: Sat Jul 09 2011