Homo Sapiens, an Endangered Species - Professor Steve Jones

I have to say I do feel a bit like an extinct species at the moment and then got up at 5:30 this morning and gone back to midwinter and southern Scotland okay I guess it seems an odd thing to call Homo sapiens an endangered species but many people certainly the 60-ton to some extent today certainly believe that he is that we are and it's very easy to find images like this on the web we have humans going extinct and being endangered and that kind of stuff because it's an old I it's wrong this it's a dystopian idea which of course is a very old one but it got new life for me in the 1960s when Paul Ehrlich who was a colleague or I was a colleague it here and I should say was wrote a book called the Population Bomb and Paul who was a great expert on butterflies and knew a lot of good biology was absolutely convinced that the human race would collapse in numbers by the year 2000 in fact he he the book was written the mid-60s and he was certain that the human population would collapse to about a million or so starving people in the year 2000 now given the way we're going at the moment that may well happen by the year 2017 but it doesn't happen yet okay I asked Paul Ehrlich after this book had been an enormous bestseller some literally zero Millions I asked him you know rudely wasn't he done with the money and he said oh I bought a private jet with it and I thought there speaks a true ecologist okay so that's the that's the background the feeling that actually we're a species that's endangering ourselves and of course not just ourselves but many other creatures - by our rush behavior such as flying back and forth from Edinburgh - glad to London and London to Glasgow in one day and they may all be some truth in that we certainly aren't teetering on extraordinary numbers and if you look at the purpose of population growth in the world you will see that in some senses at least Paul had some things are useful to say I took it took about from the origin of farming 10,000 years ago - it took it took it took 8,000 years to put on 170 million people okay then from the from the from the 1930s in the night in 1850 there were a billion people on earth in 1930 there were two billion people on earth it then by 1960 it's there were three billion people on earth and that extra billion took 30 years by 1975 there were four billion from that extra billion top 15 years by 1987 there were five billion and that took that took 12 years 1999 six billion no 12 years and 2011 seven billion 12 another 12 years so not only is the population growing but the rate of growth seems to be extending as well and it's the world it it's clear that it's going to continue there's no we're not just simply clear that it's going to continue you can see why it's going to continue most of the world has undergone what we call the demographic transition the shift from high birth rates and high death rates which characterized humans from farming until almost today too many patterns of low birth rates and low death rates that we see today and that's something very quickly much more quickly than poor anybody else expected helpmeet happening China very quickly partly of course through birth through the one-child policy but whatever the merits of that it's at least it worked it happened by choice really in India very quickly but the one place it hasn't happened is in Africa and in Africa the the the patterns of fertility are still fairly extraordinary in sub-saharan Africa and plenty of places the mean family size is is the mean family size is six or seven and death rates have dropped at birth rates haven't haven't and that this is been going on for some time which means that Africa is not only the center of world births now but is also the center of world births to come because Africa is also the center of young people this is the only the only place in the world more or less with a median age that's the age of the person halfway along the census is under 25 and over most of Africa that's true many of those under 25 year olds 13 14 15 everyone soon have children of their own so it's not surprising then that the population is plenty is set to grow to at least 9 billion and in fact the nature of the population will change because the the WHL was estimated the patterns have changed across the globe and what the one place that's rocketing up is Africa you can see at the bottom there is rocketing up that the world itself will largely under the infant impetus of African growth will peak at about 9 billion or possibly now they think even a little bit more so that clearly is something which we need to may need to be concerned about and it's not only just us who needs to be concerned about it because there are plenty of other creatures who are paying the price yes patterns of population growth in humans matched by the population patterns of extinction and those kind of those figures of extinction are really very vague I mean I'm sure there are many more extinctions and that simply because there'll be many species going extinct which we've never actually identified but clearly in Africa the fact that the fact that the population growth is greatest in Africa is bad news for our relatives the great apes which are of course after it and primates as indeed of course we are ourselves and there's this alarming truth there are now more human babies born each day 350,000 there are individuals left of all the Great Lakes combined including gorillas chimps bonobos and their items now that's quite a startling statistic and what I hope to be able to persuade you in this in this talk successfully or not I don't know that's completely new because for most of our history genetics tells us we were the endangered species we were the species that have a very low birthrate and the chimpanzees gorillas orangutans had a large and flourishing populations we only just managed to survive things have changed but I think we're very lucky all of us to be here because of the danger of extinction that we once faced and that's that's why I suggest that if we're not if we're if we are not engaged we certainly were ok so that's the that's the that's the alarming statistic and it's not good news for our friend chimpanzee because if we look at the patterns of numbers of chimpanzees in 1900 these figures are very very rough they were about a million people suggest they were about a million another less so it was 2 million by 1960 was still a million by nineteen by the 1980s it was down to about two hundred thousand by and now it's it's gradually gone up a little tiny bit it's got about 175,000 in 2003 which since 2003 it's gone down a lot and this the reason we know that is that somebody has spent a lot of time looking at the patterns of change in chimpanzee and great ape habitat okay what they say these are the declines in the types of habitats which are suitable for great apes and I won't bother you by species but these are various species chimps could bonobos gorillas and alike and if it's green things are okay if it's red things are bad and the red it comes universally from human penetration of the rainforest destroying trees burning great areas of rainforest and like and it comes largely indeed that in turn comes largely indeed from human population growth and that's the figure from 1980 to 2000 but if you progressed if you project what's going to happen to the future and it tried to do - up to 2030 effectively there's going to be no habitat suitable for great apes at all so it's quite likely that they will be if not if not extinct then very very much on the edge of extinction so again the equation has greatly changed now what I want to suggest you is that we can use principles that come from evolution and principles comes from genetics to try and infer what happened not to our own species in the past and indeed to do the same thing to what happened to these species in the past as well now everybody knows about the voyage of the Beagle and Charles Darwin's five years on was on that ship of that five years he spent just five weeks in the Galapagos aisle actually on the islands he only spent about two minutes two weeks altogether but he immediately noticed on the Galapagos the populations that lived on Islands were different from those that lived on the mainland in fact that was one of the main parts of his argument that if he looked at Galapagos plants their animals they were similar to but not the same as the plants and animals on South America and that really was the first thing that give him the idea of change before that the idea had been fixity that things could not change and he began to wonder why this was and in the 1830s he didn't have an eye you didn't he didn't know you can develop his theory and took considerably later but since then we've learned an enormous amount about the biology of islands and what we found is that as an absolute Universal the amount of inherited diversity on island populations is is far less than on the mainland okay and that's true for from things from fruit flies to lobelia plants to everything else it's also as you'll see in a moment it's also true ourselves and it has quite an interesting implication for our own history not just on islands but on the been on the mainland as well and generally there's much more genetic variation on in big populations than in small populations and if you didn't know we were on an island let's say it's rather than a stranger image to have and you simply had a DNA sequencing machine you could tell that you're on a small island because there will be less variation in the truth lies there than there were on the knee that if you would have done the experiment on the mainland so you can use this observation to try and think backwards about what the patterns of movement bottlenecks and that kind of stuff might have been for for humans and their relatives and the reason that there are smaller numbers of creatures on Islands it's simply really a matter of accident statistical sampling an accident if it's the called the bottleneck effect and I'm sure you've heard of it if you have a bottle full of yellow on blue equal numbers of yellow and blue beads and you pour ten of them into a cup it's possible you'll get five blue and five yellow but it's quite likely you'll get six and four or four and six or even eight and two and two and or two and eight every time you take a small sample it's just like spinning a penny if you only spend a penny ten times you wouldn't expect every time to get five heads and five tails if you spun a penny a hundred times you could expect pretty much to get 50 heads more or less and fifty turns okay so it's random sampling it's stochastic effects we call them in statistics now in genetics it's called as it's known as genetic drift tendency for frequency frequencies and inherited various to change when they go through small population bottlenecks okay and what we can do is a silly experiment I used to do with tiddlywinks with students or plastic bags it wasn't a very expensive experiment unfortunately this to the students over the years I've stole that all the Tippie mix down them what we do what we used to do it it's charge it's a bit infantile but actually tells you what's going on you you get you take a 50 black and 50 white tiddlywinks you put them in a plastic bag and I shake them all up and I say now they're mating and the students snigger and then I say take them out in pairs because titty titty winks like ourselves are diploid they've got two copies of every chromosome count how many black blacks black whites and white White's there are as they might be six and how many black or white variants that are there might be 60 blacks and 40 whites when you've taken it might be six packs or four whites when you're taking five pairs out so you put sixty blacks and 40 whites it back in and you just repeat the experiment and if you do it you get because of this repeated sampling in this plastic bag or or Island which is what it is what you see is so remarkably fast changes in the inherited nature of their population and nothing it's not the case that black is better than white or white is that and and black this is simple statistics this is simply being isolated and you'll see some populations begin to get more common in blacks some people get more common in white and once you hit the edge or black or white that's it you can't go anywhere you remain your completely invariant now that effect depends on the size of the sample you take if you take a small sample it happen quickly if you take an enormous sample of 2000 every generation at the bottom it happens very slowly it happens all the time but for a big population it doesn't happen very much so that's which that's what that's what genetic drift does in plastic bags and say in kind of islands but we could we can actually see the same thing going on not hip not in plastic bags but in in human populations and the advantage of humans humans really become the new fruit flies genetics when I was a student some years ago I have to tell you human genetics was almost a closed book we knew a little bit meaning we knew a little bit about blood groups I mean he was certain about about rare diseases it was a closed book really for two reasons first of all we didn't know anything not that that usually inhibits geneticists from being totally confident of what they're saying but because it had a very very dark history which I don't remind you all but it's in the early 60s and that was already really only you know only only seventeen years or so but after the closure of the extermination camps which was strongly associated with genetical ideas but things have changed so we all worked on fruit flies on my case on snows but things have changed as I say if you want to do genetics now you'd do it on humans part of the reason is that we can sequence human DNA than extraordinary rate and very very cheaply now for about a thousand dollars a person compared to a hundred million dollars a person which is what it cost twenty sixteen years ago but also um perhaps more important because in many cases we just don't have we don't just have the history written in the genes we have the history written in the books and so we can look at the books the history books the fossils the language isn't that kind of stuff and see how they fit with the records of biology and often they fit remarkably well there's a wonderful book by the gentleman who died just a couple of weeks ago reading his autobiography now which actually is rather rather surprisingly badly written he must have read in a very rush but this is all of the sacs of course these are the guy who wrote the man who mistook his wife for a hat which if you haven't read you must read it's a classic in modern English literature he's a psychiatrist and polymath and he became very interested in this island they went there and in a little book called the island of the colorblind and what's interesting about this island it's like it's in the middle of the Pacific a long way from everywhere and we know from legends that in the 18th century and there was an enormous hurricane and sighin tidal wave which had waves which washed away nearly all the islands population leaving only about a dozen people behind okay so there was a bottleneck a genuine bottleneck and if you go there now it turns out and actually it has the world's highest incidence of a very rare genetic disease called a chrome or top seer an achromatic is basically night night blindness these people cannot see so it's basically a bright light blindness these people can not see in daylight because their pupils don't respond properly they're dazzled they can't see in the dark so they can only function in the brief Twilight in the morning and in evening it's a good book because there are lots of something like a fifth of the population suffer from this it's quite a big population that's grown and it's an interesting book because it describes how they fit into society and how society has changed its its mores and its mealtimes in order to accommodate them okay but we don't know anything about the details of what happened there we don't know who who was the person who must have been carrying the gene and survived and we don't know how many people were there and however we have another case which is rather closer to home where we do know those things and I'm very glad to talk about this particular case because it allows me to put in the compulsory advertising break which every academic now has to have put into every every lecture at fifteen and thirty minutes past the hour and all the details in order to make them sure that the students are satisfied fill in the forms and take a ticket or fine I would say too many jokes when they're feeling their form but might be advertisement is that it actually has to do with my latest book which is called which is called no name for geniuses and is about the French Revolution science in the French Revolution well the French Revolution like like most revolutions ended in tears as marks said of a later French Revolution 1848 history always repeats himself itself first as tragedy and as then and then as farce the French the first French Revolution was tragedy the 1848 revolution which led to the end of the monarchy was much more of a fast but the interesting thing of course that happened after the French Revolution was we got an emperor the emperor napoleon and the emperor napoleon who was a remarkable figure and was a very good mathematician in his own right he had there isn't there is a Napoleon theorem believe it or not in the genuine years he he caused all kinds of mayhem trying to sir please try to set up a united Europe a little bit too early and led to deep splits in British political parties and was captured and sent off to exile and he was sent off on the - to exile on the island of st. Helena where he died within five years allegedly according to the French from arsenic poisoning because he it spare his death time to be full of arsenic the British did it the French say in fact that's the way that people used to preserve the relics of great men was putted in arsenic so it wasn't their fault really but he died but before he died the British were concerned that he might do what he'd done once before we should to escape from the island although it's in the middle it's the in the absolute middle of the Atlantic his previous island was famously Elba in the in the Mediterranean and Abel was I here I saw Elba not very not a bad palindrome for somebody whose first language is English aber was i ere I saw Elba he escaped from there so we put him somewhere where there was no way he could escape it's a thousand miles from land however he was known to be a good swimmer so on a garrison was then put a British garrison was then put on the island of tristan da cunha which is about as another thousand miles to the south so if he was swimming south he couldn't he couldn't get it he couldn't get a board he couldn't get it but she couldn't get a board then there's Tristan da Cunha there's where it is okay a long way from anywhere right right down in the South Atlantic and in 1840 1850 before 1816 which is where Napoleon was sent into exile it was it was it was uninhabited and in 1816 a British garrison was put on as part of a guard against Napoleon or any attempt to rescue Napoleon 1817 Napoleon died aDNA garrison was withdrawn but a Scottish corporal whose name was William glass and his wife was name was Sarah Williams stayed to set up to do some farming and their daughter they stayed and over the next 50 years about 20 more people arrived after there was a shipwreck and several of the sailors stayed they put small ads in the South African press saying why was wanted for remote island and they they got wives and they came and we know all about these people we know a great deal about their again about their about their population history and what happened was there are a number of booms and busts in that period it started off by t21 there about 15 people there and then it grew a bit quite a fertile Island people came they set up farms then in in the 1850s there very depressed pastor preacher came and he told them all no this is awful this year there's no proper religion here there's no proper Church here you don't have to leave so austere people left and there was a population crash then it grew again then the men who did a lot of fishing had a boat called the West Riding which was sunk at sea what have been left their wives left and the thing bounced around and they carried on with those kinds of numbers 60 or 80 people until the nineteen until 1961 when they were forced to move because there was a volcanic eruption and the population which was then about two hundred people all moved to Southampton ask me why okay but they did all right and and it turned out that the popper they're on population history has led to the world's highest frequency of a particular inherited disease another eye disease as it happens which is called retinoblastoma and retinal blastoma is a nasty disease it's now controllable it wasn't in 1970 was always lethal to cancer of the eye and the counselor the eye that fills the eye the eye has to be taken out and as because both eyes have that it almost always spread now it's much more controllable in fact rather in brackets it's one of the very few in which gene therapy looks as if it might indeed do something which generally generally it's promise and it turns out how to we can trace the we can trace the history of that to one of the founder individuals who were Sarah Williams who was the wife the Welsh wife as it happens of the Scots corporal William glass who first came to the island so in this case we know exactly who brought the gene and just by random chance the tiddlywink effect that gene has gone up and down and got ended up going up and it's relatively common okay so that too is a statement that a small population bottleneck long ago can have an effect on the future and the extent of the effect depends on the size of the population if a thousand people had come to Tristan zirconia there would have been no effect a midol starved of course there wouldn't be no effect because the chances of any random change of that kind would be very small and it seems highly unlikely that any large population could show this drift as it is sampling drift as it's known but that's not true because when you're trying to work out what we call the effective size okay human population or any other population you need to know not just how many people are there living in it today as in Trista and there were 200 270 at 1960 you need to know how many people lived in it in the past I'm Tristan we could do that because we've got the we've got their census records and in human populations we can often we can you know the human populations we can often do that too okay and we need a special kind of average it's not the it's not the arithmetic average it's called the harmonic mean and imagine a population in which numbers properly realistic but it's imagine the numbers of a particular population fluctuate over five generations from a thousand to a thousand to a thousand to ten there's a volcanic eruption then through through lusty efforts it rises to a thousand in the next generation again okay well what's the arithmetic me in the amp just the average is a size of the population is 802 but you missed a lot by say by just saying that because clearly what's important to the genetic future of the population is not the times when it was a thousand for the times when it was ten all right so you what you use is a special kind of statistic which is called a harmonic mean now this is actually much easier than it looks I keep telling my I keep telling my my students it consists ok the number of generations in our little example we've made it five over one over the number the first generation plus one over the number in the second generation was 1 over the number in the third generation all the way in our case to 1 over the number in the fifth generation but the thing will work for any number of generations and that's the population I imagine two thousand a thousand a thousand ten a thousand the arithmetic mean is 82 but the harmonic mean is 48 so the joy of the harmonic mean is that it's telling you that at some time in the past this population went through a bottleneck and however large it may have become today the thing which is going to influence it it's survivors it's just it's descendants is that bottleneck and we can now use we can turn the logic on its head in genetics and we can look at populations and how much variation there is and ask how much how much of a bottleneck must there be to lead to the differences let's say between this population and a population 100 miles away and I'll come back to that in a moment well there are some it's one population that illustrates that very clearly here are the a mesh the Amos char one of many what used to be many religious isolates in the in Noir in North America in North America um what there are plenty of physical islands around but I think the mental islands are even more isolated and unattainable you know in Britain there are strong social and religious barriers between from against marriages between followers of Islamic forms of Christianity say and that's really quite a that's that's not just a narrow sea that's an enormous ocean which people refuse to cross and that's also true very much in the United States it's what I like William Blake's for it Fraser it's mined forged and manacles the manacles the barriers and the prison is only in the mind but it's very very powerful okay and this is one well-known religious isolate in the United States and it's a very stringent one they they're called the anus and they fled Switzerland where they lived to escape the religious wars of the late 16th and early 17th and early 18th century they were what's called Anabaptists Anabaptists I think I'm a rather sensible philosophy which was it didn't make any sense to baptize a baby into Christ because the baby didn't know what was going on here if you were going to accept Christ by being baptized you had to do it when you were 21 when you had the ability to think whether you would actually wanted to do this or not and that seems very logical but of course to the Catholic Church that was actually an a therma many many of them were killed one standard way to kill them if somebody had been baptized as an animal was to give him a third baptism by tying a rope around his leg and throwing him in to the lake okay so he drowned them and understandably large numbers of people or numbers of people left all right and in the early 18th century a group of them not a very good big group of hundred also emigrated to Pennsylvania and when they form the close community and having been discriminated against then to get their own back to come here against everybody else because they wouldn't talk to them okay well they're an interesting lot they're still there I've I've seen them like I've seen it quite abundant on in America and they have they have remarkable desire to remain unchanged they wear the costume of the 18th century okay as you can see if they're strict believers as many of them are they refuse to use motorcars they use horses and carts instead if they're a bit if they're a bit more you know bit like what's the cool radio magic fading in and out in the Cotswolds if they're good luck beliefs aren't quite as as strong they drive cars and they'd look down on by the strict neighbors but they paint the bumpers black because it's not flashy what they called black bumper Amos all right they have a remarkable rather clever can also be about teenagers which is they say to teenagers all right we could send it to the boys of course we're gonna we're gonna send you into the wider community it's called the room Springer it means bouncing about their language is penciled in you're dutch they speak Dutch to each other light rather than Dutch Pennsylvania Dutch it's called you can go into Philadelphia whatever you like and have a wonderful time and after a year you can decide whether to stay in the outside world or come back and 80% of them come back okay now like lots and lots of lots of such isolates they're very very fake hunt here are the Pennsylvania Amish in the modern day and here are the numbers of Amy's colonies there were before 1850 some of which actually went to went to had had had had gone had gone extinct the black dots they're only about half a dozen Ames colonies by 1990 the number of colonies had rocketed up as you can see and Rajee because there's an average of six children to each family and at the present rate the numbers of a mish will be the same as the at the moment there are now two hundred twenty thousand of them if that continues if that continues until the end of the century there will be as many a mesh as there are Americans at the moment I think that's unlikely but it sort of tells you that something the power of akanda tea but if we look at the genetics of the Amish it turns out that indeed they have large numbers of otherwise rare genetic conditions because they went through a bottleneck just by chance some of the people who came carried single copies of these diseases as several people in this room carry single copies of the condition for cystic fibrosis and they don't know anything about it you need two copies for it to come together and be harmful and here are just some of them I'm missing a kind of muscular dystrophy from cradles we'll show you in a moment ad orphism probably activism of various things but you're generally speaking very rare but are relatively common in this population and in some cases they found nowhere else in the world is one of them and is from cradled and it's a it's a skeletal problem it's you can see various aspects of the bones and the like a badly damaged and there's this dwarfism cartilage hair hypoplasia which is again unique to the Amish and that comes because they went through a bottleneck and that kind of thing it's true of many religious I said it's everybody knows for example because Ashkenazi Jews tend to have relatively high frequency of the nervously generative disease known as tay-sachs disease and that's quite common among the London North London Orthodox community and that turns from the fact which is well attested from genetics that half of all the millions of Ashkenazi Jews in the world today descend from one of four women who were among the tiny group of Ashkenazi 'im who moved from Italy which is what they did in the bud Gilliam century into the Rhine Valley and into Germany and grew enormously in numbers so any population that does that is liable through the penny spinning and and the and the ebonic effect to generate its own pattern of genetic variation samba which you identify as being harmful genetic variation now so we need to take into account the the size of the bottleneck and the size of the bottleneck is actually more subtle than you think because the bottleneck refers to the reproducing population if somebody has no children you don't count them as members of the bottleneck because there they didn't reproduce and if you look in many societies today and certainly in previous days it turns out they're quite a lot of people had no children up with it another way that quite a lot of men had no children and Darwin was the first to point out that actually there's more variation in male mating success in many species than in female because the number of children of female that woman for example might have is limited by the mere facts of biology she has to become pregnant yesterday look after the infant you have to feed the infants or where as a male can have a life long room springer and leap out and nominate nominally fertilized large numbers of females it is of course the case that every time a man has sex he makes enough sperm to fertilize every woman in Europe which thank God make nobody actually does alright so um you can Counting Boris Johnson immediately so there there is potentially much more variation in male mating success than in female and that means of course that some males will not succeed in reproducing at all there's the amount of or variation is reflected by what we call sexual dimorphism among primates if the mouths of females are very different as in gorillas then only a very few males succeed in mating in chimps the differences are smaller so the inequality is smaller again and in humans it's it's fairly small here we have to individually tall people but it's clear that the male is taller than the female and more muscular and that suggests that may have been a pattern of sexual selection difference in mating patterns in the past but there are cases where the effect is really quite striking you can see that in modern developed societies there isn't really very much difference in the variation in mating success in men and women in Finland actually women have more variation in mating than men do which says something about Finnish Society in Norway which is a you know very equitable kind of place it's about it's it's about equal in the u.s. some men are fairly successful others aren't but when you go to people in Africa in Africa the Dogon live in Mali or the Archaea live in Paraguay these are these are not exactly hunter-gatherer living an early way of life then there's a big difference in the in the in the variation of men and women in mating success which means that lots of men don't get that he mates at all so a lot they're hanging around looking fierce and banging drums they're not taking part in the bottleneck so we have to discount them okay now that does happen still in recent times here's a picture of a family in holiday on holiday in Switzerland it's obviously in the 1960s as you can think as I think you could see the gentleman with a ring around his face is actually Osama bin Laden changed a bit for the years and everybody else in that picture is his brother his sister his half-brother or his half-sister and mysamma bin Laden's father Mohammed bin Laden had 22 wives and 53 children and in the year or osama's own birth he had six more children and Osama himself had last time they were counted five wives and 22 children that means that in that society there were plenty of men who had no had no sex it had no success at all and we could work out that pattern in historical terms by looking at the great signifier of maleness which is the y chromosome which as I've said into this gathering before it's very much like a surname it's a series of DNA variants that sit there there in one block so you can identify particular families and groups of Y chromosomes simply by looking at the DNA variation in them that's called a haplotype now generally speaking if I was to grind up all the men in this room we would find a quite a variety of haplotypes and that's true in many parts of the world but not all there's one part of the world where quite remarkably one y chromosome is very very common and in fact in this part of the world probably two or three hundred million men had seemed distressed his way into China a very more two or three hundred million men have the identical Y chromosome which means by definition that they descend from the same historical individual here he is Genghis Khan it's almost certainly Genghis Khan because the boundaries of that Y chromosome overlap with the boundaries of his Empire the Mongolia empire so genghis and his sons like Kublai Khan and grandsons they all had a y-chromosome they were all Hari promiscuous and they had enormous sexual success which means you know if you wanted to know how many men there were how many men how many fathers that were in that population there might be very few but thousands and thousands of mothers so you have to take that into account so that's what we do when we're working out the I'm working out the patent Ebonics so let's get to the let's cut to the chase here everybody knows that we are all Africans some of us are more Africans than others but we escaped from Africa we escaped from Africa really quite recently there something like that there are arguments about when but around 50,000 years ago I escaped from Africa and they stayed we stayed around the Middle East for a while and then in Europe about 40,000 years ago and into China actually rather earlier than that and then into the Americas only about 20,000 years ago and into into New Zealand only a thousand years ago and what we can do is make a map of the way we did it and obviously we didn't swim the Indian Ocean to get in the Pacific to get to it New Zealand we walked there okay we have to take the respect by sea but generally we walk there and what people have done is to look at human populations in relation to their distance from an arbitrary spot which is Addis Ababa in the north of Northeast Africa which is just an arbitrary spot and work out how far you would have to walk in order to get say to southern India or to the southern tip of South America and then we look at the DNA variation and we ask what are the patterns of DNA variation in those populations well the effect is really quite striking in fact it isn't really biology it's it's mathematics this is the amount of variation in the DNA in relation to the distance from abbott Addis Ababa schon now you see an absolutely striking similarity a striking tendency for the amount of variation to decrease as people moved further and further away okay and in fact by the time you get to places like the southern tip of South America and Oceania which are things like the Haiti there is only about ha a little bit more than half as much as the variation that you get in parts of Africa itself and that tells us that there have been lots and lots of bottlenecks on the way out okay we haven't moved and a great swarm out of Africa small groups have moved they broken up another small group has moved on and so on and so on every time that's happened the process I've been talking about random change has actually been taking place and we can work out the size of the of that bottleneck from the reduction in variation from one step to the next I have to tell you with some without much bitterness not watch business anyway who was the first person ever to do that that was me dammit in about 1978 with a Iranian friend of mine a physicist called Shaheen rouhani and just when the very first data on DNA variation in within an African group and a European group came out she here said him and we could work out how big the bottleneck was so he worked it out in a simplistic way and the bottleneck was 12 people for one generation or 42 people for four generations there was a call remember is very small and we published it in a little-known journal known as nature the most important scientific journal in the world and nobody ever referred to it since gambler accepted and this has become an industry doing this in a much more sophisticated way than we did it but you know I do make a point of telling this to every audience I speak but if it's this kind of thing what this kind of thing does is allow you to work out how big the bottlenecks were on each of those steps trust you see the logic it's the logic of pointing out you're on an island by finding how much reduced the variation is compared to the mainland and if it's very reduced you can work out that it must have been through a very small bottleneck and here is the pattern I don't know you can see it here and I'm going to explain this in more detail in a minute this is the these are the bottleneck sizes on each step of their journey from Africa across the world for women and shown in in red numbers and triangles and for men and what with and you can see just glancing at it that the numbers of women who move were much greater than the numbers of men and that turns on this inequality in mating success between males and females and but I look at the figures of Sagar look at the figures in some in some water so Out of Africa to the in the original bottleneck which got out of Africa this is the bottleneck which I described as being 10 when we did the harmonic main calculation okay out of Africa something like 15 men and 26 women moved from Africa and founded the world's populate the rest of the world's population which isn't very many I think you'd agree into Europe 18 men and 118 women okay so there was even more inequality and sexual success between men and women in the emerging populations of moving to Europe into India my god 74 men in 1663 women so there was an immense inequality just a few powerful men monopolized all the women and then sawn into the into the Americas 21 men and 90 women now what you can do is to complete cranking that boring equation the harmonic mean equation I'm just we're just working out what the bottleneck itself might be by adding today's populations to them how big they got over time and the effective population size of Europe is only three thousand eight hundred men and eight thousand women even today even given the millions of people who live here the effective population size of the Americas is only seven hundred men and eighteen hundred women so in fact we've all living history which turns on the random accidents of the past and indeed for much of their past we were an endangered species and we can see that actually an already strange piece of work has just come out you can now look at them you can now look at Neanderthal DNA and if you look at nan de Velde a night it turns out that the Neanderthals were very very very much in their last days very much lacking in genetic variation I won't use these are called runs of homozygosity which I won't bother you with but what this consists of if you look at the amount of variation in a Frenchman have to be a bloody Frenchman of course the high the highest the most the most the most evolved population of any and on earth okay there's French variations lots of it here are tuning guitars there's one from from the out eye and you can see it's vast segments of chromosome where there's no variation at all and that tells us that this creature was very very rare before they they just finally disappeared and they were almost none of them left so they were really going through a bottleneck which turned out to be terminal because they were then beaten out by modern humans and some people say that we got out of Africa ourselves modern humans several times and then went extinct before the population has succeeded in exploding into the world but beer that be that as it may we helped we were and endangered species now let's put on put that in to the primate context we can look at primates what we can what we can find and what we find is really rather startling I suppose is that if you look at the overall variation a sequence divergence as I would call it the amount of variation in DNA in humans and chimps and in in gorillas and the five central groups of various gangs of chimpanzees there's a striking difference humans Homo sapiens species which many of us came to claim to belong he's much less variable at the DNA low than any other large primate okay so we must have been rare for a long time when the other primates were abundant and generating lots of diversity and we can show that in different way we can draw a family tree of all modern humans and in the context of other primates this is a DNA based tree and you can see the hot modern humans they're the red the red line but red lines are very short lines which join the chimpanzees are much longer and the length of each line is a different individual person or chimp or gorilla and the longer the line the more different is from the lies that are around it okay and you can see chimpanzees are quite a very variable Gangu Tanza which you only have two individuals in this tree individuals in this graph are also very different from each other the humans are remarkably homogeneous we are the primate that did not evolve at the DNA level particularly perhaps indeed because we evolved in our minds but that's another story so and the effect is really quite striking and you could draw map of the various races of chimpanzees in East Africa we should now be extensively worked on and the difference between the purple racer which is tropic troglodyte YZ and the blue race which are almost overlaps you enter Thea if you take two populations thirty miles apart each of the different subspecies they call they're much more different genetically than the average difference between the population in France and the population popu New Guinea we are the most boring primate that has ever lived ok there's no question so they were flourishing when we were rare and if you the amount of overall variation in the in the DNA suggests that over the long term that's over the evolution of the group Homer over several years several million years the the population size didn't go much above ten to fifteen thousand people whereas the great apes they might have might have been millions of them okay so we were a rare species so so that's really is the tip my take-home lesson that we might think ourselves successful and massively abundant but in fact we are damn lucky to get at all and we may well we could have gone extinct at any time in that in that period people who creatures that face that danger now of course are not ourselves but our relatives now this is the this is an arcane bit of genetics and I can't say I fully understand it but I'll do my best people do some very very complicated number crunching on the genetics of humans and chimps and other primates to try and work out how many there had been at different times in the past and here's the timescale and it's it's it's it's it's it's it's it's logarithmic 10 to minus 2/3 or so on a time and here's that here's today and what we find is that if we look at chimpanzees that's the height of each peak is the numbers of chimpanzees which must have lived at that time and I can't understand the calculus myself so don't ask me any questions about it but people seem to believe is that people believe it's bound to be true and you can see there was for some reason we don't fully understand about 3 million years ago a big drop in the chimpanzee populations in in Africa and then there's a drop and then but until you quite recently you know historic times a thousand years ago or so ago who were quite it they were they were quite a lot of them now if he do the same for humans we had the same drop there but here we have for example a human population which are which are the Yoruba who are Nigerian group that they historically never went through a big population bottleneck and so because they were abundant in Nigeria but European populations like the French did so he can say that we really were when we put ourselves in the context of several thousand years nearly did go bust at this moment but we didn't we're still here where will you see chimpanzees in a you know in 50 years from now in a zoo that's the only place you'll see them more than likely I hope it's a nicer Zoo than this but it's at rather telling statement about the future what is now an endangered species and I slightly wonder whether we can't summarize our own future in a simple image which is this one which will make us all endangered a very different way so I'll stop there thank you

Channel: Gresham College

Views: 13,526

Rating: 4.8029556 out of 5

Keywords: Human Species, Species, genetics, Humans, Neanderthals, primates, Apes, Chimps, Chimpanzees, Endangered, genes, dna, Genetic Bottleneck, Genetic Drift, genetic variation, Genetic Diversity, Harmonic Mean, Extinction Crisis, population, Human Population, World Population, Sexual Dimorphism, Y Chromosome, Homozygosity, steve jones, medical science, gresham, gresham talk, gresham lecture, gresham medical science, professor of genetics, Genetics Professor, Genetics lecture, Genetics talk, ucl

Id: v7Nq481g-Fw

Length: 49min 15sec (2955 seconds)

Published: Thu Apr 14 2016