[murmuring crowd] jane pickering: goodevening, everyone. my name is jane pickering. i'm the executive director ofthe harvard museums of science and culture, ofwhich 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 areally fascinating evening.
i was saying to marlene i'vebeen waiting for this one. it's part of ourevolution matters series. and professormarlene zuk is going to debunk pseudo-scientificfads and show us what evolution reallytells us about sex, diet, and how we live. so that's going tobe fun, i think. before that, though, i have tosay a few more boring things. the first thing is-- andwe're very disappointed about
this-- marlene's newbook has not arrived. so we were hoping to be able tooffer book signing afterwards. if any of you havebrought one with you, i'm sure she'd behappy to sign it. but unfortunately theydidn't arrive in time for us to do that. but i do obviouslyrecommend-- i think everyone's going to berushing out to amazon or wherever by the timewe've heard this evening.
i would also like to mentionone of the special events that's coming up soon on april the20th, which is wallace day. and this is part of thecambridge science festival. and it's a day to celebrate thelife of alfred russel wallace. not as well known as charlesdarwin, but equally important, as he co-founded the theory ofevolution by natural selection. so i would encourageyou to do that. i think it's going to bea very entertaining day. and in the evening therewill be a panel discussion
that includes ed wilson. we have someone-- andyberry, who works here-- is going to be dressing upas alfred russel wallace. so it's going to bevery entertaining. i really recommend it. and i believe youcan get tickets through the cambridgescience festival also coming up onapril the 18th is a lecture by david orrell onthe past, present, and future
of prediction, which is part ofthe peabody museum's divination series. so all of our spring lecturesand classes and exhibits can be seen in our januarythrough april newsletter, which is on the side. and also for coming up,we also have our new may through augustprograms and events, which you can also getto the table on the side. and please, if you haven't letus know your email address,
please let us knowyour email address, and then we can let you knowabout the various, exciting things that are going on here. there's alsoinformation on how you can become a memberof the museum and help support all theseactivities that we do. and i would like to recognizethe sponsor for our evolution matters series, doctorsherman and joan suit, who cannot be with this, butwe're very grateful to them
for providing the support thathave enabled us to bring people like professor zuk intocambridge to give these lectures. for those of youwho 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 coupleof weeks, for you to watch on themuseum's website. so moving on totonight's speaker.
marlene zuk is a professorof ecology, evolution, and behavior at theuniversity of minnesota. and her researchinterests include sexual selection and matechoice, animal communication, the effects of parasiteson host ecology, evolution and behavior,and the conflicts between natural andsexual selection. she previously served asa professor of biology at the university of californiain riverside from 1998 to 2012.
she received her ba inbiology 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 doctoratefrom uppsala university in sweden and receiveda hood fellowship from the universityof auckland in 2007. in that same year,she was elected a fellow of the animalbehavior society.
and she became an elected fellowfor the american association for the advancementof science in 1999. she is the author of several,very popular science books. and when i list thetitles, you will see why, because you're all going to wantto rush out and read them all. i certainly am. so the first is sex on sixlegs: lessons on life, love, and language fromthe insect world. and secondly, riddled with life:friendly worms, ladybug sex,
and the parasites thatmade us who we are, which i just thinkthat's fantastic, so, anyway, the list goes on. and so let's hear fromprofessor marlene zuk. [applause] marlene zuk: thanks so muchfor the lovely introduction. and thanks so much toall of you for coming. so i am going totalk about the book. and i'm going to bereading little bits of it
and then interspersing that withexplaining some of the things from it. i want to start by showingyou the cover of the chronicle of higher education review,which featured an excerpt. and this was-- ijust thought it was kind of a striking illustrationof their concept of the book, which mercifully did notmake it to the book's cover. but i think it actuallyis somewhat relevant, because we oftenthink about evolution
over this great sweep of time,in terms of very tiny changes that happen overmillions of years. we had fins, thenthere were paws, then we evolvedopposable thumbs. and it's easy then toassume that evolution always requires eons. and that assumptionin turn makes us feel that having gonefrom 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 suitedto something more familiar in our history. and so dr. julieholland, writing in glamour magazinein september 2010 counsels that if youfeel less than human, constantly stressedand rundown, you need to remember that quote"the way so many of us are living now goesagainst our nature.
biologically wemodern homo sapiens are a lot like ourcave woman ancestors. we're animals. primates, in fact. and we have many primalneeds that get ignored. that's why the prescriptionfor good health may be as simple as asking,what would a cave woman do?" now i would also like to pointout that i never really thought that thinking aboutcave women really
involved this much cleavage. but apparently that's also partof the way people are imagining our past, is that wewere somewhat more buxom in that regard. but along similar lines,there's some comments from readers of the new yorktimes health blog, which is called "well," inwhich someone says, it "probably goes all theway back to caveman days-- the women out gatheringberries, sweeping up the place,
generally always on the run. cave mr. man outrisking his neck, hunting a sabre tooth tigeror maybe a woolly mammoth, dragging the thing home,and then collapsing in a heap on thecouch with a beer. i get it, makes sense." i'm not suggesting thatglamour magazine or the readers of the new yorktimes have pinpointed the modern dilemmain its entirety.
but it's hard to escapethis recurring conviction that somewhere, somehow, thingshave gone terribly wrong. so in a time where wehave unprecedented ability to transform theenvironment, to travel across the continent in a fewhours to make the desert bloom, we're still sufferingfrom diseases that our ancestors a fewthousand years ago-- much less our pre humanself-- never knew. diabetes, hypertension,autoimmune disorders.
there's recentdata that suggests that for the firsttime in history, maybe the members ofthe current generation are not going to live aslong as their parents. so people tend to developa nostalgia for the past. and of course, some of thatis just the same old nostalgia everybody always has, thatthere were the good old days. whether that's yourchildhood or the 1950s or in the 16th centuryor 17th century,
idealizing theso-called noble savage, someone who lived inharmony with nature, didn't destroy theirsurroundings, and so forth. and it's certainly true thathumans and the world we live in have changed very quickly. agriculture is onlyabout 10,000 years old. and there are a lot ofdiseases and societal problems that seem to have emergedjust since that time. and so it's reasonable toconclude that maybe we're
just not suited tothe way life is now. and so our health, our familylives-- maybe our sanity-- would be improvedif we could live the way that early humans did. and so in short, we have whatthe anthropologist leslie aiello, who's president ofthe renowned wenner-gren foundation, calledpaleofantasies. this is actually, incidentally--i'm a big fan of google image. i love what happens whenyou just put something in,
and you see what other people'sidea of your phrase is. and this was one of thethings that people came up with for the paleofantasies. there's not as muchcleavage in this one, make of that what you will. so she was referring tostories about human evolution that are based onlimited fossil evidence. and she said, look,do we really know what happened about brainevolution, for example?
or are we just coming upwith these paleofantasies? but i think the term appliesjust as well to the idea that our modern lives arejust out of touch with the way human beings evolved, and weneed to redress that imbalance. and so there'snewspaper articles, there's tv shows,there's dozens of books and self-help advocatespromoting all these things that we should do, whetherit comes to our diet, or barefoot running, orsleeping with our infants.
all this stuff that would bemore natural and healthier because it's more likewhat our ancestors did. now i'm anevolutionary biologist. i'm absolutely all for examininghuman health and behavior in an evolutionary context. and part of thatcontext requires understanding the environmentin which we evolved. but at the same time,what i've become interested in overthe last few years
is that we tend to have somemisconceptions about the way evolution works and aboutwhat that past was really like that can lead us astray. part of that has to do-- andpart of why the paleofantasy is a fantasy is because it kind ofassumes that humans, or maybe our proto human forebears,were at some point perfectly adaptedto our environments. and so this idea was wayback then, before agriculture or before some othernoteworthy event,
we were living on the plains, wewere in hunter gatherer groups, we were just perfectlyadapted to our environment. and it's easy to concludethat organisms are perfectly adapted to their environment. because a lot of timesyou look at living things, you look at a leafinsect, and you think it looksexactly like the leaf, down to the little tiny spotsthat it has on its wings that imitate places of rot.
so you think, oh,it's just perfect. this is absolutely whatevolution has produced is the best solution. but the problem is thatwe can admire this, but all living things arekind of full compromises. they're jury rigged. the insect has to resistdisease as well as blend into the background. and it turns out thatthe same compound that's
used to producedark spots is also necessary for theinsect immune system. so if you put a lot ofyour energy into one, you're not going to be ableto put as much into the other. and so there's allthese conflicting needs that mean there'sautomatic trade-offs, so that everythingis good enough. but it's rarely,if ever, perfect. so we've never been a seamlessmatch with our environment,
and neither is the insect. instead, our adaptation ismore like a broken zipper. so there's someteeth that align, and others that gape apart. except that it looks brokenonly to our unrealistically perfectionist eyes. eyes that themselvescontain oddly looped vessels as a holdoverfrom our evolutionary history. so we can acknowledge thatevolution is continuous.
but still it seemshard to comprehend that that means each generationcan differ infinitesimally from the one before. and there's neverthis cosmic moment when a frog or a monkey or aninsect looked down at itself and pronounced itself satisfiedand said, ok, i'm done now. i don't need to evolve anymore. so our bodies are therefore acontinuously jury rigged system with echoes inside ofus of fish or fruit
fly or lizard or mouse. and wanting to be morelike our ancestors just means wanting compromises,maybe just some different ones. so recognizing thiscontinuity of evolution also makes it clear thatit's really futile to choose a particular timein our past for human harmony. i mean, why would webe more out of sync at one particular time thanthose who came before us? did we really spend hundreds ofthousands of years in stasis,
perfectly adaptedto our environments? when during thepast could we have attained that kind oflevel of adaptation? if they'd known about evolution,would our cave dwelling forebears have feltnostalgia for the days before they were bipedal? when life was good, and thetrees were a comfort zone. i'm sure a lot of yourealize that being bipedal has meant a lot ofcompromises in our skeletons.
it's meant that we getback pain that we wouldn't have if we walked on four legs. but that doesn't meanthat being quadrupedal was more perfectthan being bipedal. scavenging prey from moreformidable predators, which is what modernhyenas will do, where they take kills thatother animals have made, is thought to havepreceded, or maybe at least accompanied, actualhunting in human history.
so were, then,those early hunter gatherers convinced that swipinga gazelle from the lion that caught it was superior somehowto this newfangled business of running it down andkilling it yourself? and why stop there? why not long to be aquatic,since life arose in the sea? so it's really hard to decidewhen exactly we should hearken back to as thisperiod of harmony, because of course,evolution is continuous.
and you might argue that huntergatherers, or the cave men of our paleofantasies,were better adapted to their environment, justbecause they spent longer at it. i mean, they were spendinglonger being hunter gatherers than we've spent sittingin front of a computer or eating candy bars. and that's certainlytrue for some attributes. but it's not truefor all of them.
selection iscontinuing in our lives as it was in thoseof our ancestors. now it's important to dispelthe myth that modern humans are operating in a completelynew environment, for one reason in particular thatpeople often bring up, which is that weonly recently began to live as long as we do now. whereas our ancestors, or maybethe average hunter gatherer, lived until they were 30 or 40.
and so therefore,we've never had to experience anythingassociated with an older age. now it's certainly truethat-- and everybody's read these stories abouthow in ancient rome the average age at death was42, or certainly average life expectancy varies acrossthe globe even now. but it's important tounderstand that an average life expectancy is just that. it's an average of allthe ages that people
were when they died. and in fact, itturns out that you can have a very low averagelife expectancy, with lots of old people. and so i'm justgoing to give you a brief illustrationof how that would be. because this is onecase where i think it actually helps togo through the math. so let us take a hypotheticalpopulation of 100 people.
and so we'll startwhen they're children, and then we'll immediatelykill half of them off. so there's 50 kids whoall die at age five, or maybe before age five,because that's a common thing to happen. they're gettingchildhood diseases. the other half survive. and in fact, the otherhalf live into adulthood. and they grow up, and they doall the things that adults do.
and they can reproduce,and so on and so forth. they all in fact regionage 60, all of them. so all of the 50 thatare left reach age 60. but at that point,sadly, 20 more of them die, so we're leftwith 30 of them. and then the remainderreach age 75. finally, at that ageall of them succumb. all right, what's theaverage life expectancy? well, you just haveto multiply that there
were 50 that died at 5, 20 thatdied at 60, 30 that died at 75. add those all upand divide by 100, because that was ouroriginal starting population. lo and behold, the averageage at death is 37. so this looks likeone of those societies that people talk about wherenobody lived very long. of course plenty ofpeople lived a long time. it's just that therewas this preponderance of kids that diedearly on in life.
and that gives you alow life expectancy. so understandingthat, i think, helps put our own modernlifespans at least in a little more perspective. old age is not arecent invention. its commonness is. nonetheless or nothingdaunted, people are still veryinterested in this idea of going back to the old times.
and in 2010, thenew york times ran an article titled "the newage caveman and the city," about modern day followers ofa supposedly evolution-based lifestyle. and these people, mainlymen, subsist largely on meat. they eschew any foods requiringthe newfangled practice of cultivation. they exercise inbursts of activity, intended to mimic a sprintafter escaping prey.
and the sydney morningherald ran a similar article, with one adherent noting quote"the theory is that you only eat what our ancestorsate 10,000 years ago. it's what you could getwith a stick in the forest." frequent blood donationis also practiced, stemming from the idea thatcavemen were often wounded, and hence blood losswould've been common. actually this photograph,which is from the new york times, university ofwisconsin anthropologist,
john hawks noted that thisphotograph kind of looks like the cast ofpleistocene twilight. [laughter] and surprisingly, newyork city turned out to be a hospitable place topractice these principles. partly because it's really easyto walk to your destinations. and one of thoseprofiled did his walking dressed in a tweed coatand italian loafers, but the lack ofadherence to an ancestral
wardrobe of presumably skinsand hides goes unremarked. this is obviouslyan exaggerated view, and the new york times articlewas kind of tongue in cheek. and even the mostardent followers of this paleo lifestyleare not really trying to liveexactly like people would have 10,000years ago or more. but again, there'sa lot of people who have an interestin trying to mimic
what life was likea long time ago. and there's lots ofblogs and websites where you can talk abouthow you might do this. there's a commenter on onesuch site, cavemanforum.com who says, "i see more andmore mistakes in moving away from paleo life. all these things we need tofeel happy, to be healthy. it sounds stupid,but i've started feeling like agriculture reallywas the biggest mistake we ever
did. of course we can'tbring the times back, but in a strangeway, i wish we could. the solutions to ourproblems lay there. not just food. i feel like we messed up,and we are paying for it." and so again, like isaid, a lot of this stuff is tongue in cheek. and i really must pointout that sometimes people
get a little aggrievedthat i'm poking fun at people who are really justtrying to tweak their diet. and no no, thisis not my intent. but i do think that there isa real kernel of commonality here, of people trying tofigure out how they can go back to a time that they perceiveas being more suited to the way we reallyought to be living. now one thing topoint out here is that we're all familiar withthese cartoons like this one.
and whenever i get bored andwant to look on the computer, i often try andfind more of these. there's tons of them. they purport to showevolutionary milestones. some of them startwith a fish that's morphing into a lizard thatcrawls onto the land, followed by various types of mammals. they almost alwaysconclude with humans. this is one of the few thatdoesn't conclude with humans.
and obviously they'retrying to make a point. the human's oftenclutching a spear. oh yeah, there's aspear in this one. and sometimes they'vegot a knuckle walking ape transforming into abeetle-browed guy with a club. and then we've got awell-muscled guy in a loin cloth and then changinginto a slouching paunchy guy bent over a computer. now i know theseare caricatures,
but they're very common. and i think they alsobetray a misconception about the way wethink about evolution. so for one thing, these thingsalmost never show women, and i have looked. the only time they showwomen is if they're trying to make a pointabout women in particular. they never show womenas people, which is sort of an interestingcommentary all by itself.
the other thing isthat they assume that we've got thisstraight line of evolution. so that one formis then replaced by a better form, which is thenreplaced by a yet better form. and so if theyconclude with people-- as they pretty much alwaysdo-- the assumption, therefore, is thatpeople are where we were supposed to end up. so therefore, we thinkthat evolution is progress.
evolution has a goal. we're trying to get somewhere. but of course that's not true. there is no progressin evolution, except in the senseof organisms becoming better adapted totheir environment. and even that's a relative term. no living thing istrying to get anywhere. and humans are notat the pinnacle
of any kind of evolutionarytree or ladder. so everything that's alivetoday is equally related-- or is equally as evolved asevery other living thing. you can't talkabout human beings as being at thepinnacle of evolution, unless you reallywant to ascribe to one of those progressions. so these cartoons,they're amusing. but they really are wrong.
so then the questionis, well, ok, did we end up gettingstuck in the stone age? what if our genes, assome people suggest, are genes that are best-suitedto many thousands of years ago? and they've somehow beenblasted-- people will sometimes talk about us having stoneage genes in the space age. we don't really call itthe space age anymore, i guess that's kindof a retro term. i don't know what we'd call it.
but the idea is that webrought our old genes into a newer environment. well, so what does itmean 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 theirancestors, and so on, ad infinitum, or atleast precambrian, or whenever life began. and some of ourgenes, therefore,
are identical to thegenes that worms have or chickens or bacteria. others arose more recently. and others aroseextremely recently. and there's a lot of newand exciting techniques that are allowing biologiststo actually pinpoint which genes are conserved, asit's called-- which genes have been kept as formsevolve into other forms-- and which are more recent.
now it's true thatrecently separated groups, like humans and apes,share more genes than do more distantrelatives, like i don't know, peopleand daffodils. but that relationship doesn'tmean that those shared genes arose at any particularpoint in our hunter gatherer past or elsewhere, andthey now can't catch up. and anthropologists beverlystrassmann and robin dunbar point out, from agenetic standpoint,
the stone age may haveno greater significance than any other period inour evolutionary past. and which genes changesis also important. people make a big deal aboutthe proverbial 98% similarity between humans and chimpanzees. and i'm sure you've all heardthat or similar metrics. people can quibble aboutwhether it's 95%, 96%, 97%-- it's a lot, ok. but that kind of add'em all up approach
is really not goingto yield any insight into what genetic differences,whether they're small or large, really mean. and so anthropologistjonathan marks points out that we shareperhaps a third of our genes with, you guessed it, daffodils. it all depends what scaleof measurement you use. and so here's aquote from his book. "so from the standpointof a daffodil,
humans and chimpanzeesaren't even 99.4% identical. they're 100% identical. the only differencebetween them is that a chimpanzeewould probably be the one eating the daffodil." so the point is that you can'treally make much of this idea that our genes are oraren't similar to what things were likein the stone age. because it's true that it'shard to find coding sequence
differences, so actualdetail differences, in the dna betweentwo modern humans. but that doesn't mean thatthe differences among us genetically are unimportant. and you can't really tell thatby just looking at the parts list, by just listing the genesand saying what's different. in other words, if allyou had was an alphabet, you could easilyend up concluding that hamlet and the scriptfor an episode of the sopranos
were the same thing, sincethey use the same letters. i mean i realize that'sa little far-fetched, but hopefully youunderstand my point. so you really don't know whatgenetic differences mean, unless you know more than justthe list of which ones exist. we also used to thinkthat evolution always meant millions and millionsof years, or at least hundreds of thousands ofyears, many millennia. but in fact, increasingly,we're discovering
that evolution-- in humans aswell as in other organisms-- can be incredibly fast. and this is actuallywhat got me into wanting to write the book is thatsome of the work that i do on insects has shown an instanceof extremely rapid evolution. and then i got interested inhow rapid evolution worked in other systems, and that endedup with me writing the book. but we're increasinglyable to discover ways that evolution canhappen quickly.
now that doesn't mean that we'veonly started discovering this recently in the last few years. in fact, we've knownabout recent evolution for quite a while. and one of theearliest examples is one that took place notactually too far from here in 1898, when there was a verybad winter storm in february in providence, rhode island,home of brown university. and hermon bumpus, who was anassistant professor of zoology
at brown wasbrought by someone-- we don't know who-- 136dead or stunned house sparrows after thisterrible winter storm had swept through providence. now i'm going to pausehere, because i've read this papera bunch of times, and i've read about bumpus'work a bunch of times. no ever explains--really, did people know that he was interestedin dead house sparrows?
like why did they do this? you don't just carryaround like 130-- that's a lot of house sparrows. you don't just carry themaround in your pockets. i mean someone had tomake a concerted effort. and you know, youneed a box, right? anyway, i've neverfigured this out. someday i'm going to try andfigure out the hermon bumpus papers and find out why he gotbrought 136 house sparrows.
but it turned outthat of the 136 house sparrows he wasbrought, half of them recovered and went offto fly away the next day. and half of them were dead. and so what bumpus did is justcompare the characteristics of the ones that survivedand the ones that died, and conclude--reasonably enough-- that the ones that survived weregoing to pass on their genes to succeeding generations.
and that there had been a shiftin the characteristics of house sparrows that had literallyoccurred overnight. and he demonstrated what'scalled stabilizing selection, which means that individualsthat were really big or really small didn't do very well. but the ones that were inthe middle of average size seemed to survive better. and so that's going to changethe genetic constituency of the population insucceeding generations.
but still, he demonstrated thatrapid evolution could happen. we also know thatrapid evolution happens in lots of othernon-human organisms, often as a result ofhuman intervention. one the best examplesof this is something that's calledfishery-induced evolution. everybody's familiarwith the idea that fishermen orcommercial fisheries will take the largestindividuals from a population
when they're fishing. the largest ones are goingto be the most profitable. but if you're a fish, andyou grow bigger with age, and as you grow bigger, thenyou achieve sexual maturity and then can produce eggsand sperm of your own-- if large individuals are beingremoved from the population before they've had a chance tosexually mature, what that does is exert selection for maturingat a smaller size and a younger age.
and so you change thewhole life history of fish when you select outthe biggest ones. it's not just that you'reremoving the big ones, and so thoseparticular individuals are no longer in the population. it's that the genes forwaiting until you're a certain size beforeyou mature have been removed fromthe population. and so the entire lifehistory of a number
of commerciallyimportant fish have been altered-- i'm notgoing to say irrevocably, but certainly for avery long time-- because of human activities. and those sorts of changespreceded the collapse of the cod fishery, forexample, in the atlantic. now it's also trueon this last point that we need to ensureit's a genetic response. sometimes fish, as wellas other organisms,
can change the age at which theymature within their lifetimes. so it's not an actual changein the genes of the population. but in other casesit absolutely is. and there's countless instancesof this in non humans, where we can demonstrate thatso-called rapid evolution-- or it's sometimes calledcontemporary evolution, it's sometimes called evolutionin ecological time scales, because it means the time scaleover which an ecologist would study a population--happens all the time.
well what about people? people, too, haveexhibited rapid evolution. because sometimespeople say, well, that's all very well for somethingthat's happening to cod, or something that'shappening to crickets, which is what i study. but really, people justcan't change that fast. that turns out not tobe the case either. the poster child forrapid 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 consumemilk when they're young, and that's whatmakes us mammals. but for all mammals otherthan people, the ability to digest milk sugar, lactose,disappears after weaning. and so consuming dairy resultsin digestive disturbances,
because we've lostlactase, the enzyme that allows us to breakdown the milk sugar. but as we're allwell-aware, and i'm sure a reasonable proportionof people in this room have demonstratedeven today, there are humans thatcan suggest dairy, without thosedigestive difficulties. it depends, however, on whereyour ancestors came from. so i love this example.
i think it's oneof the coolest ways that scientists have beenable to really pin down evolution in humans. and what we thinkhas happened is that people startedherding cattle originally not for dairy, butfor meat and hides. but when they were doingthis, if there are some people in the population that justhappen to have a gene variant that allows them tobreak down lactose--
just because populations vary,there's genetic variation in all kinds of traits-- thenthey could utilize a food source that otherpeople couldn't. furthermore, there'ssome people who believe that milkwas also advantageous because it could serve as asource of uncontaminated fluid. so both of those would havebeen an advantage thousands of years ago. and people that couldbreak down lactose
would have thrived inthe population, passed on their genesdisproportionately. that then would have encouragedmore cattle herding-- or the hurting of other milkproducing animals-- to occur, which in turn wouldmore strongly select for lactase persistence,which in turn would get people herding cattlemore, and so forth. and what we have iswhat's called gene culture coevolution.
so people sometimes say, oh,well, but humans have culture, and doesn't that meanwe can't evolve anymore. well, not at all. in fact, genes and culturecan evolve together. and so what'shappened is not only have the genes inhumans changed, but also we've selectedfor different genes in milk production and milkconstituency in our cattle. and if you look at thegeographic distribution
of where humans tend about7,000 to 10,000 years ago were herding cattle, there'sa concordance, an overlap, between where people wereherding cattle, where lactase persistencearose, and the changes in the genes from thecattle themselves. now you mightthink, oh, come on. drinking milk can'tbe that big a deal. but it turns out thatjust a 3% increase in the reproductivefitness-- the ability
to leave your genes in thenext generation-- of people who had lactase persistence. so it's not likeeverybody's dead, and only the people with lactasepersistence are surviving. it doesn't haveto work like that. just a 3% increase intheir reproductive ability can make a genelike that widespread after 300 to 350 generations. that's nothing from thestandpoint of evolution.
now worldwide today, we stillexhibit lactase persistence. there's about 35% of people allover the world that show it. so it's certainly not universal. but there's been a geneticchange, evolution, recently, in people both from partsof northern europe-- so if your ancestors arefrom northern europe, you're more likelyto have inherited a gene that allowsyou to digest lactose. also from parts of africa,where people historically
were herding cattle. i think this is justthe really cool part. so the actual genethat allows you to do this, the actual genethe lets lactose be broken up is different in thedifferent places, but it has the same effect. so what about other foods? so in other words, thebig story from this is that obviouslypeople who say, oh, we
shouldn't be consumingdairy, because it's not natural for humans. well, it wasn't then. it is now. people often want to know. the evidence isnot as clear cut. there's a reason why, like isaid, this is a poster child. we really understanda lot about how lactase persistence evolved.
but another coolthing in terms of diet is that if you come from a placewhere your ancestors have been consuming large amountsof grains and starches, you have more copies of amylase,which is another enzyme that allows you to break down starch. the neanderthals infact, it turns out-- and some other earlyhumans-- may also have consumed a lotmore grains than people previously thought they did.
so it looks like there'sbeen a lot of rapid evolution in humans, some of whichwe're only just starting to understand. now, the bigquestion that i think comes up a lot of the time iswhether human beings are still evolving. and this is a question that alot of us who work in evolution get all the time, becausepeople are saying, well, look. i understand what you're sayingabout what happened when people
were living in caves,or i understand what happened whenthere were even people living ashunter gatherers. and so that that's all fine. but now, come on,western medical care means that we are ableto survive diseases that would have killed peopleeven a few generations ago. i mean, thathypothetical population that i showed with all thefive-year-olds that died,
they died of diseasesthat five-year-olds-- at least in westernindustrialized societies-- are no longer dying from. contraception. we're controlling the degreeto which we're having children. doesn't that change evolution? well, the answer tothis is yes and no. well, the answer to arehumans still evolving is not yes or no.
the answer is yes, we are. but the degree to which westernmedical care and contraception changes things, sometimespeople overestimate that. first place, there's a lot ofpeople that don't have access to western medical careor to contraception. and diseases, thoughwe tend to forget about that living in thesociety we're now living in, is still a realthreat in the world. and ever so often when anew 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 humanbeings all over the world. so that's one caveat. and another one isremember, there's no reason to thinkthat 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 forthis, because they're showing thatevolutionary progression where you get to people,and then of course you stop. or sometimes,people will ask, oh, but what's going to bethe next form that's going to take over after people? well, it doesn't work like that. because amphibians didn't takeover from-- there's still fish.
it's just that there was afish-like ancestor, from which modern fish andamphibians both evolved. so people aren't this endpoint. and if you thinkabout it like that, then it becomes a littlesilly to talk about whether people wouldhave stopped evolving. and maybe more to the point,the real question should be-- and this quote is frommary pavelka, who's a primatologist at theuniversity of calgary.
and this is from anarticle in science. and she said, "the questionare human still evolving really should be rephrasedas, do all people have the same number of children?" well, of course they don't. and it's that differentialgenetic representation in succeedinggenerations that is going to do what evolutionalways does. it's going to changethe gene frequencies
that we're seeingin the population. so i want to give acouple of examples of what we know aboutcurrent evolution. in a way, you can thinkof lactase persistence as falling under that category. it's certainly recent evolution. but this is a studythat shows how evolution ishappening right now. so some of you maybe familiar actually
with the framinghamstudy, since it takes place in massachusetts. now it was begunin 1948 as a way to understandcardiovascular health. and the idea was tolook over the long term at health characteristicsof a large number of people and measure them over andover through their lifetime, then look at their children,measure their characteristics, and so on and so forth.
so there were lots ofmeasures like blood pressure and cholesterol taken fromthe same number of individuals from the framingham study. and these data have beenused by lots of researchers to draw lots of-- they madelots of important discoveries. this is where a lot of theinformation about genes that are associated with alzheimer'sdisease, for instance, came from. the link between sleepapnea and the likelihood
of having a stroke camefrom the framingham study. so it's been anincredibly valuable source from just a humanhealth perspective. now the scientists whobegan the framingham study were not particularly obviouslyinterested in evolution. they weren'tevolutionary biologists, they were physicians and peopleinterested in public health. but the informationfrom this study is exactly what biologistswho look for evidence
of natural selection in ananimal population would use. so now the first andsecond generations of women from the studyare now post menopausal, which means they've alreadyhad all their children. and a third generation's inthe midst of data collection and still reproducing. so this information is notterribly different than what you would collect if youwere looking at fruit flies. you're trying tounderstand whether there's
a relationship betweenthe number of offspring an individual has hadand that individual's characteristics,maybe body size. we do that when we look atfruit flies or house sparrows. and so there's heightand weight measures that were taken inthe framingham study and various health measures. so if women with acertain trait reproduce more, and thetrait itself is one
that can be passed fromparents to offspring, then we can imagine thatnatural selection's occurred. so what people have done,a team of scientists led by stephen stearns fromyale focused on the women, because their offspring,their children, are obviously more unambiguouslyable to be calculated than looking atchildren from men. and they looked atthe characteristics of those womenand their children
and how many children theyhad and then calculated-- much as you would if you hada population of fruit flies or some otherorganism-- what was going to happen in the future. so first of all, they foundthat over the generations it looks like the ageat first childbirth seems to be going down. so people were havingchildren younger, which was kind of a surpriseto some of the investigators.
the age at menopausewas going up. and then they were able tobasically predict the future. they were able tosay, all right, what's the population going tolook like in 10 generations? turns out that thewomen of framingham, assuming they all--and of course, this assumes that theenvironment's the same, and that we're not changingany of the selective forces-- the women of framinghamare going to be shorter.
they're going to bea little bit plumper. they're going to havelower cholesterol, and they're going to havelower blood pressure. they're going tochange evolutionarily. and the leader of the studysaid that natural selection is acting on thishuman population to cause slow, gradual,evolutionary change. now like i said, this assumesthe environment stays the same. and there's othercaveats in there.
so nobody's saying that they'regoing to predict it absolutely down to the millimeter. but these sorts of dataare really an exciting way to understand how humanevolution is still proceeding. and there's otherlong term studies like that in other parts ofthe world that are coming up with similar sortsof ways of analyzing what's happening to humans. another example takesplace very far away,
in a different placefar away and also used a very different wayof studying this. the framinghamstudy is basically using tools that wereavailable to hermon bumpus. but in this case,we're able to use some more modern genetictools to understand exactly what's happened tochange the human genome. and this has to do withaltitude adaptation in the mountains of tibet.
there are populationsof tibetan natives who live at altitudesof 13,000 feet. and as you know,that's ordinarily really hard on people. they have altitudesickness, they have all kinds ofother compromises to their physiologythat can result in reduced fertility for women. women will havedifficulty getting
pregnant at highaltitudes and so forth. these tibetan nativesdon't experience these sorts of effects. and they don't getaltitude sickness. they have a fasterbreathing rate, but-- and this isa key point-- they don't show an increase inthe amount of hemoglobin or the amount of redblood cells they have. and this isn'tsomething that just
happens as they're growing up. this genetic change happened aslittle as 3,000 to 7,000 years ago, which again,is incredibly rapid. and what's interestinghere is that if you compare the genes of thosetibetans with ethnic hans from china who are alsoliving at high altitudes, the genes are different. the tibetans have agene variant that's associated with the productionof actually less hemoglobin.
now this sounds kindof counter intuitive. but in fact, havingless hemoglobin turns out to be agood thing for them, because it means that theyavoid a problem that's associated withhaving too thick blood and having too manyred blood cells. now think about this. now we know that humansevolved at sea level. if you're at sea level and youincrease your hemoglobin when
oxygen is low-- so if youhave a low amount of oxygen in your bloodstream,and you just ramp up the amountof hemoglobin you're producing-- that will counteractmild anemia, which is usually the reason why atsea level you would have low levels of oxygen. but altitudesickness will not be helped by increasing hemoglobin. because all that doesis thicken your blood.
and the problemisn't that you don't have enough oxygenin your bloodstream, it's that there isn'tenough oxygen in the air. now evolution of coursedoesn't know, so to speak, why your blood oxygen decreased. so if you just havea 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 lowerhemoglobin levels will help, because it willallow the hemoglobin that you do have to flow moreefficiently and allows you to avoid the effectsof altitude sickness. now this brings up thelast point i want to make, which is that this kind oftinkering around with the way hemoglobin works is probablynot what you would have come up with, if you wouldhave said, ok, we
need to build ahuman being that's going to be able tolive at 13,000 feet, and this whole bloodcirculatory thing needs to work. you would not have come upwith let's lower the amount of hemoglobin they have. but that's because natureis not an engineer. nature's a tinkerer. and this phrase isfrom francois jacob, who's a french nobel laureate,who wrote a very famous paper
in the journal sciencein 1977, where-- that's the phrase he used, thatevolution is a tinkerer, not an engineer. an engineer starts withwhat they want to achieve and then gets the partstogether to come up with the best possible solution. a tinkerer just says what'slying around in the garage? i'm going to use that tocome up with the solution. and i'm going to takethe parts i have to hand.
and that's what nature does. so that evolution'salways working off of these existing parts. it's not like you're startingfrom scratch every time you make an organism. and that's why,like i was saying, we're carrying withus the genes of fish and daffodils andbacteria, which have been kind ofmishmoshed together.
and then some of themhave changed very rapidly to produce what we are now. but all of thatdepended on the parts that were lyingaround in the garage. so the final pointis that evolution really just-- you justhave to make it work. it just has to be good enough. oh, so sorry, youmust all be asleep. so the discountliquors thing came
because seriously, if yougoogle rapid evolution-- i have no explanation for this. but you get this thingfor discount liquors. so the fact that nobodyseemed to respond to that either means thatyou really trusted that i was going to tie thisin really well, or people are not paying attention. so this is just some ofthe stuff that came up. and so again, there's thisidea that organisms are simply
not in perfect harmonywith their environment. because being in perfectharmony would not have come up with asolution like the hemoglobin for the tibetans. it's just that it's good enough. now people really likebeing recently evolved or evolving really well. what was funny aboutthe tibet story when it was releasedjust a year or two ago
is that everybodywanted to call it the fastest case of humanevolution on record, as if like we'rekind of in this race. and people are trying to getcredit for having-- like now, all of the sudden, evolvingquickly is a virtue. and there really aren'tany prizes for this. and if there wereactually, if there were a prize for mostrecently evolved, of course, i'm sure you all realizewho would get them.
it would be a microbe, becauseour disease-causing organisms are always evolving veryrapidly, more rapidly than we are, which is oneof the reasons we have difficulty incontrolling them. so if you really want togive a prize to somebody for being mostrecently evolved, you can give it to the aids virus. but that's probablynot something anybody's all that eager to do.
so people arecompetitive, and we all know people are competitive. but what's wrong withthis, about thinking about what evolved more quickly? there was actuallya paleontologist in an article aboutthe fate of humans. a paleontologistsaid 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 problemis that this kind of goal-directed thinking,it still presents evolution like it's this processwith an endpoint. because being goodat something suggests that there's a skillthat you can master. and then onceyou've mastered it, you can move onto something else. we're done evolving, nowwe can all learn to knit
or-- i don't knowwhat we're going to do when we'redone with evolving. but of course our ancestorswere also evolving. and no organism isgoing to get to a point of perfect adaptation, becauseno organism in the past was at a point of perfectadaptation either. nobody heaves this sigh ofgenetic relief and then stops. all of our characteristicsand all of our genes are subject to changeat different rates.
and so you can't ever say,ok i'm done with this. so the greekphilosopher heraclitus, i'm sure you all have heard,was supposed to have said, no man ever steps inthe same river twice. now he was known, incidentally,as heraclitus the obscure, in part becausemany of his works were difficult to interpret. and indeed, thereare people that suggest that this sayingmeans that nothing
retains its identity. while others claim heraclitusmeant that because life is constantly changing, onecan always reinvent oneself. now as applied to evolution,one could interpret his remark to mean that organisms areresponding to a continually changing environment,the river, and hence evolution itselfis continual too. but to truly emulateevolution, the river would need to be unending, andthe foot that stepped into it
would need to be differentwith every attempted wading. not only are our lives differentfrom those of our pleistocene ancestors, but their liveswere different from those of their ancestors aswell, and on it goes. so sometimes you reallycan't talk about evolution as resulting in somethingthat's going to be better or something that'sgoing to be worse. sometimes evolution just endsup in resulting in more change. thank you very much.
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