The human journey-- a genetic odyssey: Spencer Wells at TEDxConnecticutCollege

hello everybody good weather anyway it's wonderful to be here I'd like to thank the organizers for doing such an amazing job so thanks a lot guys so it's well come through the first slide so I am a population geneticist really a geneticist and anthropologist now population geneticist sounds kind of scary and technical what does that mean well my overarching goal my theme that I investigate as a scientist is the patterns of human diversity around the world we are an incredibly diverse species you travel walk down the street in the major city you see people who seem to be so different from each other and from ourselves and we're also distributed everywhere we're a global species and this is something where you know I read a lot of kind of accounts of early explorers Captain Cook and so on when I was younger and these guys were like cruising around the world 18th century they crash ashore on some island in the South Pacific and they see people living there and they never kind of questioned why that was and they noticed that they were somewhat similar to people they'd seen elsewhere but different in some ways as well really the goal of our research as population geneticists at least human population geneticists is to try and answer the question of ok how did we become such a globally distributed species so that's the big overarching theme of our work but like any big theme in science you could break it down into sub themes or questions that you can chip away at using the tools of generating data hypotheses coming down on one side or the other first question we can ask is one of origins are we in fact all related to each other and if so how closely the second is a question of journey if we do spring from a common source as a species how do we come to occupy every corner of the globe in the process of generating these patterns of diversity that we see today well historically the way this has been approached is by going out and digging things up out of the ground stones and bones archaeology and paleoanthropology and saying largely in the basis of morphology this looks a little bit more like my cousin Fred then that does this is the missing link this is where we originated this is the origin of our species what I'd like to suggest though is that while the field of paleoanthropology in particular gives us lots of fascinating possibilities about our origins as a species and some insights possibly into the journey question doesn't give us the probabilities about direct lines of descent that we really want possibilities but not probabilities well this is a great example what you're looking at here three extinct species of hominid potential human ancestors from left to right Homo erectus Homo habilis and Paranthropus boisei I say that three times fast robust australopithecine all uncovered from the same location in northern kenya and all dating to roughly the same time about two million years ago so we've got three potential ancestors living in the same place at the same time that means not all three could have left descendants down to me which one of these guys am I actually directly biologically connected to I don't know possibilities about our history but not the probabilities about direct lines of descent that we really want well we as a putnis as a field of population geneticists take a different approach we really kind of turned the question on its head instead of going out and digging things up out of the past and guessing at how they may or may not connect up to the present and to us we start in the present and we work our way back in time because we know that we all had parents and those parents had parents and their parents had parents and so on so there is an unbroken biological lineage going back in time now genealogy really popular hobby I'm sure lots of people in the audience have constructed family trees and go back maybe five possibly ten generations do we want to see a I guess that's why they're raising the lights a second most popular hobby after gardening apparently it's boys ever take gardening untold but the point is that no matter how far back you can trace your family history in the written record ultimately that written record runs out and we hit what the genealogists call a brick wall and beyond that we simply simply entered this dark and mysterious realm we call history and in my case ultimately prehistory but it turns out we're all carrying something inside of ourselves which is in effect a written historical document in our DNA and that allows us to see back beyond the written record beyond that brick wall back to the very earliest days of our species and start to get the answer to these questions of origins and journeys well quick primer on DNA for those of you who have not taken a molecular genetics course recently you know who you are there's gonna be a quiz at the end so anyway long linear molecule the famous double helix described by Watson and Crick back in 1953 composed of four subunits we denote them AC G and T and it's the sequence of these A's C's GS and T's that basically provides a blueprint to make another version of you and their billions of these a C's GS and T's in the human genome it's a lot of information if you took all of the DNA out of one tiny microscopic cell in your body it would be about 6 feet long so it's a huge amount of information in every generation you've got to copy all of this information to pass it on to your kids and you've got to copy it in about 8 hours which is how long it takes your cells to replicate your DNA and it's really important so you want to get it right so it's like copying the longest book you can imagine so think for a really long book war and peace imagine a thousand volumes of that and so you've got to copy that by hand in eight hours what are you gonna do well you're gonna get your Red Bull or coffee or whatever you choose to drink and you're gonna sit there and go back and forth and check and double check to make sure you get this information right but inevitably what's gonna happen as you're doing this you can make a type of spelling mistake that happens at the DNA level as well they're called mutations and they occurred a low but a measurable rate of around a hundred mutations per genome per generation so every child is carrying around a hundred novel changes these typos in their DNA relative to their parents clicking off in a clock like fashion every generation now when these these typos or mutations get passed down through the generations they become markers of descent so it turns out if you share one of these changes in your DNA with another person you share an ancestor the person in the past you first had that change in their DNA and passed it on to the two of you and that's how we can connect people up into ever deeper branches of the human family tree now what do these markers actually look like well this is an example of actual DNA sequencing data five individuals lined up here one two three four five same region of the genome has been sequenced they've been aligned reading down through the sequences the first thing you'll notice is they basically look identical GC c TG c CT and so on that's the first thing that comes out of every single one of our studies of human genetic variation humans are 99.9 percent identical at the DNA level we only differ on average at one in every thousand nucleotide positions from someone were not even related to that's actually a remarkably low level of genetic variation compared to our great ape cousins so the gorillas the chimps the orangutans have between four and ten times as much genetic variation as we do and we think of them as being on the brink of extinction or at least endangered this is a sign actually of a near extinction event that our species went through about 70,000 years ago when the total number of human beings alive on earth dropped down to as few as 2,000 2,000 people we came back from that and we still carry the signals of that near extinction event in our DNA with this low level of variation so it's quite difficult to find these genetic markers but if you look carefully enough down here in this region gee gee gee gee gee gee gee a gee a single letter change from a G to an A that's an example of a genetic marker if you shared that a with someone else you share an ancestor person who first had that change and passed it on to the two of you now by asking a very open-ended question sampling people from all over the world looking at their pattern of genetic markers asking how does the tree fall out what is the what is the pattern we see in the tree we've been able to construct family trees for everybody alive today everybody in this room in fact everybody walking around on planet Earth falls somewhere onto one of the branches of these family trees we focused in particular on two pieces of DNA that are proven to be really important for our understanding of origins and journey mitochondrial DNA mtDNA on the left this trace is a purely matter in a lineage everybody's carrying this but only women pass it on okay so tells you about your mom's side of the family your mother's mothers and mothers and mothers mother all the way back to the very first mother the equivalent on the male side is known as the Y chromosome and it's a little chunk of DNA that makes men men doesn't really have that much going for it apart from that not that many genes channel-surfing refusal ask for directions when you're lost a few other male traits but basically it determines maleness and it of course is passed on from fathers to son so it traces a purely pattern a line of descent tells you by your father's father's father's father's father so by looking at the pattern of genetic markers and people from all over the world again we've been able to construct family trees for everybody alive now these are actually really simplified versions of the trees that we use and we're constructing the laboratory analyses going out in the field and looking at new DNA samples but they still look kind of complicated sitting out there in the audience a little bit blurry let's combine them simplify them even more turn them on their side so that the roots at the bottom of the branches are coming off the top what's the take-home message here well it's that the longest branches both the male and female sides the longest branches in these family trees are found only in African populations and because the lengths of the branches are proportional to the number of these mutational changes that we've had over time ticking off in that clock like fashion what that means is that Africans had been accumulating genetic diversity for longer than any other group and therefore that our species originated in Africa well this isn't actually a new idea even Darwin suggested this over a century ago he said well you know as most of the great apes we most likely came from Africa if you take in physical anthropology a generation ago you would have learned about Homo erectus leaving Africa perhaps millions of years ago and spreading out and evolving separately around the world into human races as they still called them at that time what's the what's most amazing from the DNA analysis though is how recently we all share in African origin within the last 200,000 years we originated in Africa as a species and it's only within the last sixty thousand years or so 2,000 human generations that we've left that continent to populate the rest of the world evidences that there was an early coastal migration that moved through the bab-el-mandeb Strait through the Arabian Peninsula down through India Southeast Asia reaching Australia the ancestors of the Aborigines by around fifty thousand years ago a slightly later inland migration through the Middle East into Central Asia by 40,000 years ago westward into Europe by 30,000 and a small intrepid group of explorers Wanderers if you will touching on the theme of the conference today crossing a short-lived land bridge the bering land bridge between the old and the new worlds moving into the americas between 15 and 20 thousand years ago during the last glacial maximum and piecing together the details of these stories not only the initial settlement and the timing of these events but also much more recent migration events which were a little bit more difficult to decipher is the goal of the Genographic project which i direct from the National Geographic Society now there are three core components to what we're doing in the project at its heart it's a research effort misses field research that's being carried out by myself by my team of collaborators around the world human population geneticists focusing on indigenous and traditional populations living in their particular corner of the globe North America South America sub-saharan Africa and so on now why are indigenous and traditional groups so important to this work well think about your own ancestry I'll think about mine out loud I have ancestors from all over northern and western Europe and I live in eastern seaboard of North America down in Washington DC National Geographic headquarters what is my DNA tell you about the ancient history of any of these places it's really hard to tell I'm a mutt all the recent migrations kind of mixed up the story and that's the case for so many of us today what we ideally want are people who retain the link to their geography and to their ancestors and their ancestors genetic patterns that many of the rest of us have lost and those are the world's indigenous and traditional peoples forming the heart of what we're doing scientifically but when we were designing the project we didn't want it to just be the history of the world's hundred million 200 million indigenous people we wanted to be the story of all of us all 7.1 billion of us so we wanted to open it up to members of the general public who can go onto our website find out more about the project and purchase a kid this is all done anonymously you can join the project and figure out how you fit into this growing family tree of humanity and join a real-time scientific project which is kind of cool doesn't happen very often you can't actually be there on the ground with a Mars rover mission or as part of the Human Genome Project but in this case he can actually be a part of the science moreover by doing that this is all nonprofit you helped to fund the field research we're doing with the indigenous populations as well as the third component of the project the Legacy Fund and this is the grant giving entity within the project the names to give something tangible back to the world's indigenous and traditional peoples many of whom have a way of life that's endangered today we are actually going through a period of cultural mass extinction at the moment the parallels the biodiversity crisis linguist tell us that of the 6,000 some odd languages spoken in the world today by the end of the century between half and 90% will no longer be spoken they'll be gone we're losing a language every two weeks there a process that makes sense people leave behind their ancient villages they move to a melting pot city Mumbai sub hollow place like that when they do their kids enter the melting pot they stop learning the the old language the traditional ways and within a generation soo that culture is endangered or extinct so through these grants led by the communities themselves we're trying to raise awareness about this and to do something to slow it or even to halt it if we can and we've given out 85 grants through 2013 2.2 million dollars so far just some examples of projects were funding an effort to save the egg no B language which was once the lingua franca of the Silk Road now spoken by only about 1,500 people in Tajikistan project to preserve traditional Aboriginal dance patterns in the northern territories of Australia their song lines the healing journey a project to raise awareness about environmental issues along the Yukon River collaboration among several tribal groups up there and an interesting project with the Schwar people of Ecuador trying to preserve their ethno botanical knowledge which of course includes many medicinal plants as well so just some examples of some of the projects that we're funding now I'm often asked by people what's the biggest surprise that's come out of the project and for me there been lots of scientific discoveries but the most exciting thing has been the power of what I like to call citizen science and citizen science has talked about more and more these days getting the general public actively engaged in the scientific effort not just by providing lots of data and they certainly have so 600,000 people have purchased our kids so far which has been a tremendous success really launched this whole field of consumer genetic testing but it's the active engagement of the part of people who are curious about their results and actually helping to drive forward the science and this is a great example this came to light by accident actually woman wrote into the project a couple of years ago and said listen love what you guys are doing lots of members of my extended family have taken part but in my case you seem to have gotten it wrong you need to retest me because you told me that I'm carrying a Central Asian or a Siberian mitochondrial DNA lineage I know for a fact that I'm European my ancestors came from a little village just outside of Budapest I can show you church records going back to the sixteenth century so clearly I've got to have European DNA please retest me thank you very much now when I heard this I got really excited not because I like retesting people and infected of course the results were correct but rather because Hungarians are really interesting population within Europe most of Europe's languages including the language I'm speaking now French German Italian Russian languages spoken down in India Hindi Farsi spoken in Iran all belonged to a language family known as indo-european and it's a Western Eurasian group of languages that all ultimately trace back to a common source several thousand years ago but within Europe there are a couple of outliers there's Basque which is unrelated to any other language as far as we can tell could have been brought here from Mars linguistic isolate and then there's Hungarian and Hungarian actually is related to other languages finish and the Sami language spoken by the LAT people in northern Scandinavia the finno-ugric branch of what's called the Uralic language family and as the name your Alex suggests the centre of diversity is over around the Ural Mountains are east of there in Siberia it's really a Siberian language family and this makes sense because we know the Magyar people migrated into the Central European Plains about a thousand years ago bring with them the Hungarian culture the Hungarian language they settled down had a tremendous cultural impact a complete shift in the language from whatever was spoken there before there should have been a genetic impact as well problem is when we've gone in and done the typical sampling that you do in these studies 50 75 people we haven't seen any trace of these Central Asian or Siberian genetic lineages but when this woman wrote in about her result we pulled the data that we had in the database we had 2300 people in the public side with Hungarian ancestry and we're seeing at a very low level but a detectable level now two to three percent on both the male and female sides the Central Asian or Siberian genetic lineages the power of citizen science not only the power of large numbers but the power of a person's curiosity to draw our awareness to a new genetic pattern and we've built this into the next phase of the project which launched about a year and a half ago Geno 2.0 very much trying to make use of the citizen science component to get people actively involved in the research leveraging those samples and the insights from the first phase improving the technology a new DNA testing chip that we've designed from the ground up but really harnessing the power of the community and the users to learn new things about the genetic patterns so you can go in and share your stories see how you compare to other people in the database even find out how Neanderthal you are it turns out if you're non African you're carrying around 2% in the and earth all DNA we met the Neanderthals and interbred with them about fifty to sixty thousand years ago so with that I will end there I've got the flashing screen over here if you're interested in finding out more about the project there's the URL check it out thank you

Channel: TEDx Talks

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Keywords: connecticut college, ted talk, tedx talk, spencer wells, tedx, not all who wander, ted, Genetics (Field Of Study), TEDx, tedx talks, ted x, science, ted talks

Id: xnbxrDGZoBQ

Length: 19min 14sec (1154 seconds)

Published: Mon May 05 2014