Marlene Zuk

Transcription

[MURMURING CROWD] JANE PICKERING: Good evening, everyone. My name is Jane Pickering. I'm the executive director of the Harvard Museums of Science and Culture, of which the Harvard Museum of Natural History, the sponsor for this evening's event, is one of those museums. So I'd like to welcome you all. I think we're in for a really fascinating evening. I was saying to Marlene I've been waiting for this one. It's part of our Evolution Matters series. And Professor Marlene Zuk is going to debunk pseudo-scientific fads and show us what evolution really tells us about sex, diet, and how we live. So that's going to be fun, I think. Before that, though, I have to say a few more boring things. The first thing is-- and we're very disappointed about this-- Marlene's new book has not arrived. So we were hoping to be able to offer book signing afterwards. If any of you have brought one with you, I'm sure she'd be happy to sign it. But unfortunately they didn't arrive in time for us to do that. But I do obviously recommend-- I think everyone's going to be rushing out to Amazon or wherever by the time we've heard this evening. I would also like to mention one of the special events that's coming up soon on April the 20th, which is Wallace Day. And this is part of the Cambridge Science Festival. And it's a day to celebrate the life of Alfred Russel Wallace. Not as well known as Charles Darwin, but equally important, as he co-founded the theory of evolution by natural selection. So I would encourage you to do that. I think it's going to be a very entertaining day. And in the evening there will be a panel discussion that includes Ed Wilson. We have someone-- Andy Berry, who works here-- is going to be dressing up as Alfred Russel Wallace. So it's going to be very entertaining. I really recommend it. And I believe you can get tickets through the Cambridge Science Festival Also coming up on April the 18th is a lecture by David Orrell on the past, present, and future of prediction, which is part of the Peabody Museum's Divination series. So all of our spring lectures and classes and exhibits can be seen in our January through April newsletter, which is on the side. And also for coming up, we also have our new May through August programs and events, which you can also get to the table on the side. And please, if you haven't let us know your email address, please let us know your email address, and then we can let you know about the various, exciting things that are going on here. There's also information on how you can become a member of the museum and help support all these activities that we do. And I would like to recognize the sponsor for our Evolution Matters series, Doctors Herman and Joan Suit, who cannot be with this, but we're very grateful to them for providing the support that have enabled us to bring people like Professor Zuk into Cambridge to give these lectures. For those of you who are interested, or when you get home, say to someone, you know, you really should have come, all the lectures are available online within a couple of weeks, for you to watch on the museum's website. So moving on to tonight's speaker. Marlene Zuk is a professor of ecology, evolution, and behavior at the University of Minnesota. And her research interests include sexual selection and mate choice, animal communication, the effects of parasites on host ecology, evolution and behavior, and the conflicts between natural and sexual selection. She previously served as a professor of biology at the University of California in Riverside from 1998 to 2012. She received her BA in biology from the University of California in Santa Barbara, obtained her PhD In zoology from the University of Michigan, and completed her post-doc work at the University of New Mexico. She has an honorary doctorate from Uppsala University in Sweden and received a Hood Fellowship from the University of Auckland in 2007. In that same year, she was elected a fellow of the Animal Behavior Society. And she became an elected fellow for the American Association for the Advancement of Science in 1999. She is the author of several, very popular science books. And when I list the titles, you will see why, because you're all going to want to rush out and read them all. I certainly am. So the first is Sex on Six Legs: Lessons on Life, Love, and Language from the Insect World. And secondly, Riddled with Life: Friendly Worms, Ladybug Sex, and the Parasites that Made Us Who We Are, which I just think that's fantastic, so, anyway, the list goes on. And so let's hear from Professor Marlene Zuk. [APPLAUSE] MARLENE ZUK: Thanks so much for the lovely introduction. And thanks so much to all of you for coming. So I am going to talk about the book. And I'm going to be reading little bits of it and then interspersing that with explaining some of the things from it. I want to start by showing you the cover of the Chronicle of Higher Education Review, which featured an excerpt. And this was-- I just thought it was kind of a striking illustration of their concept of the book, which mercifully did not make it to the book's cover. But I think it actually is somewhat relevant, because we often think about evolution over this great sweep of time, in terms of very tiny changes that happen over millions of years. We had fins, then there were paws, then we evolved opposable thumbs. And it's easy then to assume that evolution always requires eons. And that assumption in turn makes us feel that having gone from savanna to asphalt in a mere few thousand years, we must be kind of caught out by the pace of modern life. We'd be much better suited to something more familiar in our history. And so Dr. Julie Holland, writing in Glamour Magazine in September 2010 counsels that if you feel less than human, constantly stressed and rundown, you need to remember that quote "the way so many of us are living now goes against our nature. Biologically we modern Homo sapiens are a lot like our cave woman ancestors. We're animals. Primates, in fact. And we have many primal needs that get ignored. That's why the prescription for good health may be as simple as asking, what would a cave woman do?" Now I would also like to point out that I never really thought that thinking about cave women really involved this much cleavage. But apparently that's also part of the way people are imagining our past, is that we were somewhat more buxom in that regard. But along similar lines, there's some comments from readers of the New York Times health blog, which is called "Well," in which someone says, it "probably goes all the way back to caveman days-- the women out gathering berries, sweeping up the place, generally always on the run. Cave Mr. Man out risking his neck, hunting a sabre tooth tiger or maybe a woolly mammoth, dragging the thing home, and then collapsing in a heap on the couch with a beer. I get it, makes sense." I'm not suggesting that Glamour magazine or the readers of The New York Times have pinpointed the modern dilemma in its entirety. But it's hard to escape this recurring conviction that somewhere, somehow, things have gone terribly wrong. So in a time where we have unprecedented ability to transform the environment, to travel across the continent in a few hours to make the desert bloom, we're still suffering from diseases that our ancestors a few thousand years ago-- much less our pre human self-- never knew. Diabetes, hypertension, autoimmune disorders. There's recent data that suggests that for the first time in history, maybe the members of the current generation are not going to live as long as their parents. So people tend to develop a nostalgia for the past. And of course, some of that is just the same old nostalgia everybody always has, that there were the good old days. Whether that's your childhood or the 1950s or in the 16th century or 17th century, idealizing the so-called noble savage, someone who lived in harmony with nature, didn't destroy their surroundings, and so forth. And it's certainly true that humans and the world we live in have changed very quickly. Agriculture is only about 10,000 years old. And there are a lot of diseases and societal problems that seem to have emerged just since that time. And so it's reasonable to conclude that maybe we're just not suited to the way life is now. And so our health, our family lives-- maybe our sanity-- would be improved if we could live the way that early humans did. And so in short, we have what the anthropologist Leslie Aiello, who's president of the renowned Wenner-Gren Foundation, called paleofantasies. This is actually, incidentally-- I'm a big fan of Google image. I love what happens when you just put something in, and you see what other people's idea of your phrase is. And this was one of the things that people came up with for the paleofantasies. There's not as much cleavage in this one, make of that what you will. So she was referring to stories about human evolution that are based on limited fossil evidence. And she said, look, do we really know what happened about brain evolution, for example? Or are we just coming up with these paleofantasies? But I think the term applies just as well to the idea that our modern lives are just out of touch with the way human beings evolved, and we need to redress that imbalance. And so there's newspaper articles, there's TV shows, there's dozens of books and self-help advocates promoting all these things that we should do, whether it comes to our diet, or barefoot running, or sleeping with our infants. All this stuff that would be more natural and healthier because it's more like what our ancestors did. Now I'm an evolutionary biologist. I'm absolutely all for examining human health and behavior in an evolutionary context. And part of that context requires understanding the environment in which we evolved. But at the same time, what I've become interested in over the last few years is that we tend to have some misconceptions about the way evolution works and about what that past was really like that can lead us astray. Part of that has to do-- and part of why the paleofantasy is a fantasy is because it kind of assumes that humans, or maybe our proto human forebears, were at some point perfectly adapted to our environments. And so this idea was way back then, before agriculture or before some other noteworthy event, we were living on the plains, we were in hunter gatherer groups, we were just perfectly adapted to our environment. And it's easy to conclude that organisms are perfectly adapted to their environment. Because a lot of times you look at living things, you look at a leaf insect, and you think it looks exactly like the leaf, down to the little tiny spots that it has on its wings that imitate places of rot. So you think, oh, it's just perfect. This is absolutely what evolution has produced is the best solution. But the problem is that we can admire this, but all living things are kind of full compromises. They're jury rigged. The insect has to resist disease as well as blend into the background. And it turns out that the same compound that's used to produce dark spots is also necessary for the insect immune system. So if you put a lot of your energy into one, you're not going to be able to put as much into the other. And so there's all these conflicting needs that mean there's automatic trade-offs, so that everything is good enough. But it's rarely, if ever, perfect. So we've never been a seamless match with our environment, and neither is the insect. Instead, our adaptation is more like a broken zipper. So there's some teeth that align, and others that gape apart. Except that it looks broken only to our unrealistically perfectionist eyes. Eyes that themselves contain oddly looped vessels as a holdover from our evolutionary history. So we can acknowledge that evolution is continuous. But still it seems hard to comprehend that that means each generation can differ infinitesimally from the one before. And there's never this cosmic moment when a frog or a monkey or an insect looked down at itself and pronounced itself satisfied and said, OK, I'm done now. I don't need to evolve anymore. So our bodies are therefore a continuously jury rigged system with echoes inside of us of fish or fruit fly or lizard or mouse. And wanting to be more like our ancestors just means wanting compromises, maybe just some different ones. So recognizing this continuity of evolution also makes it clear that it's really futile to choose a particular time in our past for human harmony. I mean, why would we be more out of sync at one particular time than those who came before us? Did we really spend hundreds of thousands of years in stasis, perfectly adapted to our environments? When during the past could we have attained that kind of level of adaptation? If they'd known about evolution, would our cave dwelling forebears have felt nostalgia for the days before they were bipedal? When life was good, and the trees were a comfort zone. I'm sure a lot of you realize that being bipedal has meant a lot of compromises in our skeletons. It's meant that we get back pain that we wouldn't have if we walked on four legs. But that doesn't mean that being quadrupedal was more perfect than being bipedal. Scavenging prey from more formidable predators, which is what modern hyenas will do, where they take kills that other animals have made, is thought to have preceded, or maybe at least accompanied, actual hunting in human history. So were, then, those early hunter gatherers convinced that swiping a gazelle from the lion that caught it was superior somehow to this newfangled business of running it down and killing it yourself? And why stop there? Why not long to be aquatic, since life arose in the sea? So it's really hard to decide when exactly we should hearken back to as this period of harmony, because of course, evolution is continuous. And you might argue that hunter gatherers, or the cave men of our paleofantasies, were better adapted to their environment, just because they spent longer at it. I mean, they were spending longer being hunter gatherers than we've spent sitting in front of a computer or eating candy bars. And that's certainly true for some attributes. But it's not true for all of them. Selection is continuing in our lives as it was in those of our ancestors. Now it's important to dispel the myth that modern humans are operating in a completely new environment, for one reason in particular that people often bring up, which is that we only recently began to live as long as we do now. Whereas our ancestors, or maybe the average hunter gatherer, lived until they were 30 or 40. And so therefore, we've never had to experience anything associated with an older age. Now it's certainly true that-- and everybody's read these stories about how in ancient Rome the average age at death was 42, or certainly average life expectancy varies across the globe even now. But it's important to understand that an average life expectancy is just that. It's an average of all the ages that people were when they died. And in fact, it turns out that you can have a very low average life expectancy, with lots of old people. And so I'm just going to give you a brief illustration of how that would be. Because this is one case where I think it actually helps to go through the math. So let us take a hypothetical population of 100 people. And so we'll start when they're children, and then we'll immediately kill half of them off. So there's 50 kids who all die at age five, or maybe before age five, because that's a common thing to happen. They're getting childhood diseases. The other half survive. And in fact, the other half live into adulthood. And they grow up, and they do all the things that adults do. And they can reproduce, and so on and so forth. They all in fact region age 60, all of them. So all of the 50 that are left reach age 60. But at that point, sadly, 20 more of them die, so we're left with 30 of them. And then the remainder reach age 75. Finally, at that age all of them succumb. All right, what's the average life expectancy? Well, you just have to multiply that there were 50 that died at 5, 20 that died at 60, 30 that died at 75. Add those all up and divide by 100, because that was our original starting population. Lo and behold, the average age at death is 37. So this looks like one of those societies that people talk about where nobody lived very long. Of course plenty of people lived a long time. It's just that there was this preponderance of kids that died early on in life. And that gives you a low life expectancy. So understanding that, I think, helps put our own modern lifespans at least in a little more perspective. Old age is not a recent invention. Its commonness is. Nonetheless or nothing daunted, people are still very interested in this idea of going back to the old times. And in 2010, The New York Times ran an article titled "The New Age Caveman and the City," about modern day followers of a supposedly evolution-based lifestyle. And these people, mainly men, subsist largely on meat. They eschew any foods requiring the newfangled practice of cultivation. They exercise in bursts of activity, intended to mimic a sprint after escaping prey. And the Sydney Morning Herald ran a similar article, with one adherent noting quote "the theory is that you only eat what our ancestors ate 10,000 years ago. It's what you could get with a stick in the forest." Frequent blood donation is also practiced, stemming from the idea that cavemen were often wounded, and hence blood loss would've been common. Actually this photograph, which is from The New York Times, University of Wisconsin anthropologist, John Hawks noted that this photograph kind of looks like the cast of Pleistocene Twilight. [LAUGHTER] And surprisingly, New York City turned out to be a hospitable place to practice these principles. Partly because it's really easy to walk to your destinations. And one of those profiled did his walking dressed in a tweed coat and Italian loafers, but the lack of adherence to an ancestral wardrobe of presumably skins and hides goes unremarked. This is obviously an exaggerated view, and The New York Times article was kind of tongue in cheek. And even the most ardent followers of this paleo lifestyle are not really trying to live exactly like people would have 10,000 years ago or more. But again, there's a lot of people who have an interest in trying to mimic what life was like a long time ago. And there's lots of blogs and websites where you can talk about how you might do this. There's a commenter on one such site, cavemanforum.com who says, "I see more and more mistakes in moving away from paleo life. All these things we need to feel happy, to be healthy. It sounds stupid, but I've started feeling like agriculture really was the biggest mistake we ever did. Of course we can't bring the times back, but in a strange way, I wish we could. The solutions to our problems lay there. Not just food. I feel like we messed up, and we are paying for it." And so again, like I said, a lot of this stuff is tongue in cheek. And I really must point out that sometimes people get a little aggrieved that I'm poking fun at people who are really just trying to tweak their diet. And no no, this is not my intent. But I do think that there is a real kernel of commonality here, of people trying to figure out how they can go back to a time that they perceive as being more suited to the way we really ought to be living. Now one thing to point out here is that we're all familiar with these cartoons like this one. And whenever I get bored and want to look on the computer, I often try and find more of these. There's tons of them. They purport to show evolutionary milestones. Some of them start with a fish that's morphing into a lizard that crawls onto the land, followed by various types of mammals. They almost always conclude with humans. This is one of the few that doesn't conclude with humans. And obviously they're trying to make a point. The human's often clutching a spear. Oh yeah, there's a spear in this one. And sometimes they've got a knuckle walking ape transforming into a beetle-browed guy with a club. And then we've got a well-muscled guy in a loin cloth and then changing into a slouching paunchy guy bent over a computer. Now I know these are caricatures, but they're very common. And I think they also betray a misconception about the way we think about evolution. So for one thing, these things almost never show women, and I have looked. The only time they show women is if they're trying to make a point about women in particular. They never show women as people, which is sort of an interesting commentary all by itself. The other thing is that they assume that we've got this straight line of evolution. So that one form is then replaced by a better form, which is then replaced by a yet better form. And so if they conclude with people-- as they pretty much always do-- the assumption, therefore, is that people are where we were supposed to end up. So therefore, we think that evolution is progress. Evolution has a goal. We're trying to get somewhere. But of course that's not true. There is no progress in evolution, except in the sense of organisms becoming better adapted to their environment. And even that's a relative term. No living thing is trying to get anywhere. And humans are not at the pinnacle of any kind of evolutionary tree or ladder. So everything that's alive today is equally related-- or is equally as evolved as every other living thing. You can't talk about human beings as being at the pinnacle of evolution, unless you really want to ascribe to one of those progressions. So these cartoons, they're amusing. But they really are wrong. So then the question is, well, OK, did we end up getting stuck in the Stone Age? What if our genes, as some people suggest, are genes that are best-suited to many thousands of years ago? And they've somehow been blasted-- people will sometimes talk about us having Stone Age genes in the Space Age. We don't really call it the Space Age anymore, I guess that's kind of a retro term. I don't know what we'd call it. But the idea is that we brought our old genes into a newer environment. Well, so what does it mean to actually say that our genes are old, but our environment is new? Our genes, of course, came from our ancestors, who got them from their ancestors, and so on, ad infinitum, or at least Precambrian, or whenever life began. And some of our genes, therefore, are identical to the genes that worms have or chickens or bacteria. Others arose more recently. And others arose extremely recently. And there's a lot of new and exciting techniques that are allowing biologists to actually pinpoint which genes are conserved, as it's called-- which genes have been kept as forms evolve into other forms-- and which are more recent. Now it's true that recently separated groups, like humans and apes, share more genes than do more distant relatives, like I don't know, people and daffodils. But that relationship doesn't mean that those shared genes arose at any particular point in our hunter gatherer past or elsewhere, and they now can't catch up. And anthropologists Beverly Strassmann and Robin Dunbar point out, from a genetic standpoint, the Stone Age may have no greater significance than any other period in our evolutionary past. And which genes changes is also important. People make a big deal about the proverbial 98% similarity between humans and chimpanzees. And I'm sure you've all heard that or similar metrics. People can quibble about whether it's 95%, 96%, 97%-- it's a lot, OK. But that kind of add 'em all up approach is really not going to yield any insight into what genetic differences, whether they're small or large, really mean. And so anthropologist Jonathan Marks points out that we share perhaps a third of our genes with, you guessed it, daffodils. It all depends what scale of measurement you use. And so here's a quote from his book. "So from the standpoint of a daffodil, humans and chimpanzees aren't even 99.4% identical. They're 100% identical. The only difference between them is that a chimpanzee would probably be the one eating the daffodil." So the point is that you can't really make much of this idea that our genes are or aren't similar to what things were like in the Stone Age. Because it's true that it's hard to find coding sequence differences, so actual detail differences, in the DNA between two modern humans. But that doesn't mean that the differences among us genetically are unimportant. And you can't really tell that by just looking at the parts list, by just listing the genes and saying what's different. In other words, if all you had was an alphabet, you could easily end up concluding that Hamlet and the script for an episode of The Sopranos were the same thing, since they use the same letters. I mean I realize that's a little far-fetched, but hopefully you understand my point. So you really don't know what genetic differences mean, unless you know more than just the list of which ones exist. We also used to think that evolution always meant millions and millions of years, or at least hundreds of thousands of years, many millennia. But in fact, increasingly, we're discovering that evolution-- in humans as well as in other organisms-- can be incredibly fast. And this is actually what got me into wanting to write the book is that some of the work that I do on insects has shown an instance of extremely rapid evolution. And then I got interested in how rapid evolution worked in other systems, and that ended up with me writing the book. But we're increasingly able to discover ways that evolution can happen quickly. Now that doesn't mean that we've only started discovering this recently in the last few years. In fact, we've known about recent evolution for quite a while. And one of the earliest examples is one that took place not actually too far from here in 1898, when there was a very bad winter storm in February in Providence, Rhode Island, home of Brown University. And Hermon Bumpus, who was an assistant professor of zoology at Brown was brought by someone-- we don't know who-- 136 dead or stunned house sparrows after this terrible winter storm had swept through Providence. Now I'm going to pause here, because I've read this paper a bunch of times, and I've read about Bumpus' work a bunch of times. No ever explains-- really, did people know that he was interested in dead house sparrows? Like why did they do this? You don't just carry around like 130-- that's a lot of house sparrows. You don't just carry them around in your pockets. I mean someone had to make a concerted effort. And you know, you need a box, right? Anyway, I've never figured this out. Someday I'm going to try and figure out the Hermon Bumpus papers and find out why he got brought 136 house sparrows. But it turned out that of the 136 house sparrows he was brought, half of them recovered and went off to fly away the next day. And half of them were dead. And so what Bumpus did is just compare the characteristics of the ones that survived and the ones that died, and conclude-- reasonably enough-- that the ones that survived were going to pass on their genes to succeeding generations. And that there had been a shift in the characteristics of house sparrows that had literally occurred overnight. And he demonstrated what's called stabilizing selection, which means that individuals that were really big or really small didn't do very well. But the ones that were in the middle of average size seemed to survive better. And so that's going to change the genetic constituency of the population in succeeding generations. But still, he demonstrated that rapid evolution could happen. We also know that rapid evolution happens in lots of other non-human organisms, often as a result of human intervention. One the best examples of this is something that's called fishery-induced evolution. Everybody's familiar with the idea that fishermen or commercial fisheries will take the largest individuals from a population when they're fishing. The largest ones are going to be the most profitable. But if you're a fish, and you grow bigger with age, and as you grow bigger, then you achieve sexual maturity and then can produce eggs and sperm of your own-- if large individuals are being removed from the population before they've had a chance to sexually mature, what that does is exert selection for maturing at a smaller size and a younger age. And so you change the whole life history of fish when you select out the biggest ones. It's not just that you're removing the big ones, and so those particular individuals are no longer in the population. It's that the genes for waiting until you're a certain size before you mature have been removed from the population. And so the entire life history of a number of commercially important fish have been altered-- I'm not going to say irrevocably, but certainly for a very long time-- because of human activities. And those sorts of changes preceded the collapse of the cod fishery, for example, in the Atlantic. Now it's also true on this last point that we need to ensure it's a genetic response. Sometimes fish, as well as other organisms, can change the age at which they mature within their lifetimes. So it's not an actual change in the genes of the population. But in other cases it absolutely is. And there's countless instances of this in non humans, where we can demonstrate that so-called rapid evolution-- or it's sometimes called contemporary evolution, it's sometimes called evolution in ecological time scales, because it means the time scale over which an ecologist would study a population-- happens all the time. Well what about people? People, too, have exhibited rapid evolution. Because sometimes people say, well, that's all very well for something that's happening to cod, or something that's happening to crickets, which is what I study. But really, people just can't change that fast. That turns out not to be the case either. The poster child for rapid human evolution is the ability to consume dairy. Now other mammals, as I'm sure you're all aware-- well, all mammals. And humans are mammals too. So all mammals consume milk when they're young, and that's what makes us mammals. But for all mammals other than people, the ability to digest milk sugar, lactose, disappears after weaning. And so consuming dairy results in digestive disturbances, because we've lost lactase, the enzyme that allows us to break down the milk sugar. But as we're all well-aware, and I'm sure a reasonable proportion of people in this room have demonstrated even today, there are humans that can suggest dairy, without those digestive difficulties. It depends, however, on where your ancestors came from. So I love this example. I think it's one of the coolest ways that scientists have been able to really pin down evolution in humans. And what we think has happened is that people started herding cattle originally not for dairy, but for meat and hides. But when they were doing this, if there are some people in the population that just happen to have a gene variant that allows them to break down lactose-- just because populations vary, there's genetic variation in all kinds of traits-- then they could utilize a food source that other people couldn't. Furthermore, there's some people who believe that milk was also advantageous because it could serve as a source of uncontaminated fluid. So both of those would have been an advantage thousands of years ago. And people that could break down lactose would have thrived in the population, passed on their genes disproportionately. That then would have encouraged more cattle herding-- or the hurting of other milk producing animals-- to occur, which in turn would more strongly select for lactase persistence, which in turn would get people herding cattle more, and so forth. And what we have is what's called gene culture coevolution. So people sometimes say, oh, well, but humans have culture, and doesn't that mean we can't evolve anymore. Well, not at all. In fact, genes and culture can evolve together. And so what's happened is not only have the genes in humans changed, but also we've selected for different genes in milk production and milk constituency in our cattle. And if you look at the geographic distribution of where humans tend about 7,000 to 10,000 years ago were herding cattle, there's a concordance, an overlap, between where people were herding cattle, where lactase persistence arose, and the changes in the genes from the cattle themselves. Now you might think, oh, come on. Drinking milk can't be that big a deal. But it turns out that just a 3% increase in the reproductive fitness-- the ability to leave your genes in the next generation-- of people who had lactase persistence. So it's not like everybody's dead, and only the people with lactase persistence are surviving. It doesn't have to work like that. Just a 3% increase in their reproductive ability can make a gene like that widespread after 300 to 350 generations. That's nothing from the standpoint of evolution. Now worldwide today, we still exhibit lactase persistence. There's about 35% of people all over the world that show it. So it's certainly not universal. But there's been a genetic change, evolution, recently, in people both from parts of northern Europe-- so if your ancestors are from northern Europe, you're more likely to have inherited a gene that allows you to digest lactose. Also from parts of Africa, where people historically were herding cattle. I think this is just the really cool part. So the actual gene that allows you to do this, the actual gene the lets lactose be broken up is different in the different places, but it has the same effect. So what about other foods? So in other words, the big story from this is that obviously people who say, oh, we shouldn't be consuming dairy, because it's not natural for humans. Well, it wasn't then. It is now. So what about other foods? People often want to know. The evidence is not as clear cut. There's a reason why, like I said, this is a poster child. We really understand a lot about how lactase persistence evolved. But another cool thing in terms of diet is that if you come from a place where your ancestors have been consuming large amounts of grains and starches, you have more copies of amylase, which is another enzyme that allows you to break down starch. The Neanderthals in fact, it turns out-- and some other early humans-- may also have consumed a lot more grains than people previously thought they did. So it looks like there's been a lot of rapid evolution in humans, some of which we're only just starting to understand. Now, the big question that I think comes up a lot of the time is whether human beings are still evolving. And this is a question that a lot of us who work in evolution get all the time, because people are saying, well, look. I understand what you're saying about what happened when people were living in caves, or I understand what happened when there were even people living as hunter gatherers. And so that that's all fine. But now, come on, Western medical care means that we are able to survive diseases that would have killed people even a few generations ago. I mean, that hypothetical population that I showed with all the five-year-olds that died, they died of diseases that five-year-olds-- at least in Western industrialized societies-- are no longer dying from. Contraception. We're controlling the degree to which we're having children. Doesn't that change evolution? Well, the answer to this is yes and no. Well, the answer to are humans still evolving is not yes or no. The answer is yes, we are. But the degree to which Western medical care and contraception changes things, sometimes people overestimate that. First place, there's a lot of people that don't have access to Western medical care or to contraception. And diseases, though we tend to forget about that living in the society we're now living in, is still a real threat in the world. And ever so often when a new form of flu comes out, someone will say, oh yes, but remember the days-- and they're not so distant-- when infectious diseases were an enormous problem for human beings all over the world. So that's one caveat. And another one is remember, there's no reason to think that evolution would have stopped for people. Because those cartoons-- remember the cartoons. The cartoons are wrong. The cartoons show that, OK-- the cartoons are also partly responsible for this, because they're showing that evolutionary progression where you get to people, and then of course you stop. Or sometimes, people will ask, oh, but what's going to be the next form that's going to take over after people? Well, it doesn't work like that. Because amphibians didn't take over from-- there's still fish. It's just that there was a fish-like ancestor, from which modern fish and amphibians both evolved. So people aren't this endpoint. And if you think about it like that, then it becomes a little silly to talk about whether people would have stopped evolving. And maybe more to the point, the real question should be-- and this quote is from Mary Pavelka, who's a primatologist at the University of Calgary. And this is from an article in Science. And she said, "the question are human still evolving really should be rephrased as, do all people have the same number of children?" Well, of course they don't. And it's that differential genetic representation in succeeding generations that is going to do what evolution always does. It's going to change the gene frequencies that we're seeing in the population. So I want to give a couple of examples of what we know about current evolution. In a way, you can think of lactase persistence as falling under that category. It's certainly recent evolution. But this is a study that shows how evolution is happening right now. So some of you may be familiar actually with the Framingham study, since it takes place in Massachusetts. Now it was begun in 1948 as a way to understand cardiovascular health. And the idea was to look over the long term at health characteristics of a large number of people and measure them over and over through their lifetime, then look at their children, measure their characteristics, and so on and so forth. So there were lots of measures like blood pressure and cholesterol taken from the same number of individuals from the Framingham study. And these data have been used by lots of researchers to draw lots of-- they made lots of important discoveries. This is where a lot of the information about genes that are associated with Alzheimer's disease, for instance, came from. The link between sleep apnea and the likelihood of having a stroke came from the Framingham study. So it's been an incredibly valuable source from just a human health perspective. Now the scientists who began the Framingham study were not particularly obviously interested in evolution. They weren't evolutionary biologists, they were physicians and people interested in public health. But the information from this study is exactly what biologists who look for evidence of natural selection in an animal population would use. So now the first and second generations of women from the study are now post menopausal, which means they've already had all their children. And a third generation's in the midst of data collection and still reproducing. So this information is not terribly different than what you would collect if you were looking at fruit flies. You're trying to understand whether there's a relationship between the number of offspring an individual has had and that individual's characteristics, maybe body size. We do that when we look at fruit flies or house sparrows. And so there's height and weight measures that were taken in the Framingham study and various health measures. So if women with a certain trait reproduce more, and the trait itself is one that can be passed from parents to offspring, then we can imagine that natural selection's occurred. So what people have done, a team of scientists led by Stephen Stearns from Yale focused on the women, because their offspring, their children, are obviously more unambiguously able to be calculated than looking at children from men. And they looked at the characteristics of those women and their children and how many children they had and then calculated-- much as you would if you had a population of fruit flies or some other organism-- what was going to happen in the future. So first of all, they found that over the generations it looks like the age at first childbirth seems to be going down. So people were having children younger, which was kind of a surprise to some of the investigators. The age at menopause was going up. And then they were able to basically predict the future. They were able to say, all right, what's the population going to look like in 10 generations? Turns out that the women of Framingham, assuming they all-- and of course, this assumes that the environment's the same, and that we're not changing any of the selective forces-- the women of Framingham are going to be shorter. They're going to be a little bit plumper. They're going to have lower cholesterol, and they're going to have lower blood pressure. They're going to change evolutionarily. And the leader of the study said that natural selection is acting on this human population to cause slow, gradual, evolutionary change. Now like I said, this assumes the environment stays the same. And there's other caveats in there. So nobody's saying that they're going to predict it absolutely down to the millimeter. But these sorts of data are really an exciting way to understand how human evolution is still proceeding. And there's other long term studies like that in other parts of the world that are coming up with similar sorts of ways of analyzing what's happening to humans. Another example takes place very far away, in a different place far away and also used a very different way of studying this. The Framingham study is basically using tools that were available to Hermon Bumpus. But in this case, we're able to use some more modern genetic tools to understand exactly what's happened to change the human genome. And this has to do with altitude adaptation in the mountains of Tibet. There are populations of Tibetan natives who live at altitudes of 13,000 feet. And as you know, that's ordinarily really hard on people. They have altitude sickness, they have all kinds of other compromises to their physiology that can result in reduced fertility for women. Women will have difficulty getting pregnant at high altitudes and so forth. These Tibetan natives don't experience these sorts of effects. And they don't get altitude sickness. They have a faster breathing rate, but-- and this is a key point-- they don't show an increase in the amount of hemoglobin or the amount of red blood cells they have. And this isn't something that just happens as they're growing up. This genetic change happened as little as 3,000 to 7,000 years ago, which again, is incredibly rapid. And what's interesting here is that if you compare the genes of those Tibetans with ethnic Hans from China who are also living at high altitudes, the genes are different. The Tibetans have a gene variant that's associated with the production of actually less hemoglobin. Now this sounds kind of counter intuitive. But in fact, having less hemoglobin turns out to be a good thing for them, because it means that they avoid a problem that's associated with having too thick blood and having too many red blood cells. Now think about this. Now we know that humans evolved at sea level. If you're at sea level and you increase your hemoglobin when oxygen is low-- so if you have a low amount of oxygen in your bloodstream, and you just ramp up the amount of hemoglobin you're producing-- that will counteract mild anemia, which is usually the reason why at sea level you would have low levels of oxygen. But altitude sickness will not be helped by increasing hemoglobin. Because all that does is thicken your blood. And the problem isn't that you don't have enough oxygen in your bloodstream, it's that there isn't enough oxygen in the air. Now evolution of course doesn't know, so to speak, why your blood oxygen decreased. So if you just have a rule of thumb that says, OK, oxygen is low, I'm going to make more hemoglobin, that's great at sea level because it'll help with anemia. But at high altitudes, not having this response and having lower hemoglobin levels will help, because it will allow the hemoglobin that you do have to flow more efficiently and allows you to avoid the effects of altitude sickness. Now this brings up the last point I want to make, which is that this kind of tinkering around with the way hemoglobin works is probably not what you would have come up with, if you would have said, OK, we need to build a human being that's going to be able to live at 13,000 feet, and this whole blood circulatory thing needs to work. You would not have come up with let's lower the amount of hemoglobin they have. But that's because nature is not an engineer. Nature's a tinkerer. And this phrase is from Francois Jacob, who's a French Nobel laureate, who wrote a very famous paper in the journal Science in 1977, where-- that's the phrase he used, that evolution is a tinkerer, not an engineer. An engineer starts with what they want to achieve and then gets the parts together to come up with the best possible solution. A tinkerer just says what's lying around in the garage? I'm going to use that to come up with the solution. And I'm going to take the parts I have to hand. And that's what nature does. So that evolution's always working off of these existing parts. It's not like you're starting from scratch every time you make an organism. And that's why, like I was saying, we're carrying with us the genes of fish and daffodils and bacteria, which have been kind of mishmoshed together. And then some of them have changed very rapidly to produce what we are now. But all of that depended on the parts that were lying around in the garage. So the final point is that evolution really just-- you just have to make it work. It just has to be good enough. Oh, so sorry, you must all be asleep. So the Discount Liquors thing came because seriously, if you Google rapid evolution-- I have no explanation for this. But you get this thing for Discount Liquors. So the fact that nobody seemed to respond to that either means that you really trusted that I was going to tie this in really well, or people are not paying attention. So this is just some of the stuff that came up. And so again, there's this idea that organisms are simply not in perfect harmony with their environment. Because being in perfect harmony would not have come up with a solution like the hemoglobin for the Tibetans. It's just that it's good enough. Now people really like being recently evolved or evolving really well. What was funny about the Tibet story when it was released just a year or two ago is that everybody wanted to call it the fastest case of human evolution on record, as if like we're kind of in this race. And people are trying to get credit for having-- like now, all of the sudden, evolving quickly is a virtue. And there really aren't any prizes for this. And if there were actually, if there were a prize for most recently evolved, of course, I'm sure you all realize who would get them. It would be a microbe, because our disease-causing organisms are always evolving very rapidly, more rapidly than we are, which is one of the reasons we have difficulty in controlling them. So if you really want to give a prize to somebody for being most recently evolved, you can give it to the AIDS virus. But that's probably not something anybody's all that eager to do. So people are competitive, and we all know people are competitive. But what's wrong with this, about thinking about what evolved more quickly? There was actually a paleontologist in an article about the fate of humans. A paleontologist said that humans are first class evolvers. You know like, OK, this is now something else we've got to be good at. But you know the problem is that this kind of goal-directed thinking, it still presents evolution like it's this process with an endpoint. Because being good at something suggests that there's a skill that you can master. And then once you've mastered it, you can move on to something else. We're done evolving, now we can all learn to knit or-- I don't know what we're going to do when we're done with evolving. But of course our ancestors were also evolving. And no organism is going to get to a point of perfect adaptation, because no organism in the past was at a point of perfect adaptation either. Nobody heaves this sigh of genetic relief and then stops. All of our characteristics and all of our genes are subject to change at different rates. And so you can't ever say, OK I'm done with this. So the Greek philosopher Heraclitus, I'm sure you all have heard, was supposed to have said, no man ever steps in the same river twice. Now he was known, incidentally, as Heraclitus the obscure, in part because many of his works were difficult to interpret. And indeed, there are people that suggest that this saying means that nothing retains its identity. While others claim Heraclitus meant that because life is constantly changing, one can always reinvent oneself. Now as applied to evolution, one could interpret his remark to mean that organisms are responding to a continually changing environment, the river, and hence evolution itself is continual too. But to truly emulate evolution, the river would need to be unending, and the foot that stepped into it would need to be different with every attempted wading. Not only are our lives different from those of our Pleistocene ancestors, but their lives were different from those of their ancestors as well, and on it goes. So sometimes you really can't talk about evolution as resulting in something that's going to be better or something that's going to be worse. Sometimes evolution just ends up in resulting in more change. Thank you very much. [APPLAUSE]