Spencer Wells construye un árbol genealógico para toda la humanidad. TED 2007 Español Sub

[Music] [Music] [Applause] jumbo bonjour Zas too these are a few of the languages that uh I've spoken little bits of over the course of the last 6 weeks as I've been to 17 countries I think I'm up to on this crazy tour I've been doing uh checking out various aspects of the project that we're doing that I'm going to tell you a little bit about later on and visiting some pretty incredible places places like Mongolia Cambodia New Guinea South Africa Tanzania twice I was here a month ago and the opportunity to make a whirlwind tour of the world like that is utterly amazing for lots of reasons you see some incredible stuff and you get to make these spot comparisons between people all around the globe and the thing that you really take away from that the kind of surface thing that you take away from it is not that we're all one although I'm going to tell you about that but rather how different we are there is so much diversity around the globe 6,000 different languages spoken by 6 and a half billion people all different colors shapes sizes you walk down the street in any big city you travel like that and you are amazed at the diversity in the human species how do we explain that diversity well that's what I'm going to talk about today is how we're using the tools of genetics population genetics in particular to tell us how we generated this diversity and how long it took now the problem of human diversity like all big scientific questions how do you explain something like that can be broken down into sub questions and you can faret away at those little sub questions first one is uh really a question of Origins do we all share a common orig origin in fact and given that we do and that's the Assumption everybody I think in this room would make when when was that when did we originate as a species how long have we been diverging from each other and the second question is related but slightly different if we do spring from a common source how did we come to occupy every corner of the globe and in the process generate all of this diversity the different ways of life the different appearances the different languages around the world well the question of Origins as with so many other questions in biology seems to have been answered by Darwin over a century ago in The Descent of Man he wrote in each great region of the world the living mammals are closely related to the extinct species of the same region it's therefore probable that Africa was formerly inhabited by extinct Apes closely Allied to the gorilla and chimpanzee and as these two species are now men's nearest allies it's somewhat more probable that our early progenitors lived on the African continent than elsewhere so we're done we can go home finish the uh origin question well not quite because Darwin was talking about our distant ancestry our common ancestry with apes and it is quite clear that Apes originated on the African continent around 23 million years ago they appear in the fossil record Africa was actually disconnected from the other land masses at that time due to the vagaries of plate tectonics floating around the Indian Ocean bumped into Eurasia around 16 million years ago and then we had the first African Exodus as we call it the Apes that left at that time ended up in Southeast Asia became the Gibbons and the orangutans and the ones that stayed on in Africa evolved into the gorillas the chimpanzees and us so yes if you're talking about our ancestry with Apes it's very clear by looking at the fossil record we started off here but that's not really the question I'm asking I'm asking about our human ancestry things that we would recognize as being like us if they were sitting here in the room they were peering over your shoulder you wouldn't leap back like that what about our human ancestry because if we go far enough back we share a common ancestry with every living thing on Earth DNA ties us all together so we share ancestry with Barracuda and bacteria and mushrooms if you go far of back over a billion years what we're asking about though is human ancestry how do we study that well historically it has been studied using the science of paleoanthropology digging things up out of the ground and largely on the basis of morphology the way things are shaped often skull-shaped saying this looks a little bit more like us than that so this must be my ancestor this must be who I'm directly descended from the field of paleoanthropology I'll argue gives us lots of fascinating possibilities about our ancestry but it doesn't give us the probabilities that we really want as scientists what do I mean by that you're looking at a great example here these are three extinct species of ped potential human ancestors all dug up just west of here in oldi Gorge by The Leaky family and they're all dating to roughly the same time from left to right we've got homoerectus homohabilis and Australopithecus now called paranthropus Boi robust osine three extinct species same place same time that means that not all three could be my direct ancestor which one of these guys am I actually related to possibilities about our ancestry but not the probabilities that we're really looking for Well a different approach has been to look at morphology in humans using the only data that people really had at hand until quite recently again largely skull shaped the first person to do this systematically was Lenas Carl Van Lin Swedish botanist who in the 18th century took it upon himself to categorize every living organism on the planet you think you've got a tough job and he did a pretty good job he categorized about 12,000 species in systemet he actually coined the term homo sapiens means wise man in Latin but looking around the world at the diversity of humans he said well you know we seem to come in discreet subspecies or categories and he talked about Africans and Americans and Asians and Europeans in a blatantly racist category he term monstrosus which basically included all the people he didn't like including imaginary folk like [Applause] elves uh it's it's easy to dismiss this as the perhaps well-intentioned But ultimately bited musings of an 18th century scientist working in the pre- darwinian era except if you had taken physical anthropology as recently as 20 or 30 years ago in many cases you would have learned basically that same classification of humanity human races that according to physical anthropologists of 30 40 years ago Carlton is the best example had been diverging from each other this was in the post darwinian era for over a million years since the time of homo erectus but based on what data very little very little morphology and a lot of guesswork well what I'm going to talk about today what I'm going to talk about now is a new approach to this problem instead of going out and guessing about our ancestry digging things up out of the ground possible ancestors and saying on the basis of morphology which we still don't completely understand we don't know the genetic causes underlying most morphological variation what we need to do is turn the problem on its head because what we're really asking is a genealogical problem or a genealogical question what we're trying to do is construct a family tree for everybody alive today and as any genealogist will tell you anybody have member of the family or maybe you've tried to construct a family tree Trace back in time you start in the present with relationships you're certain about you and your sibling share a parent in common you and your cousin share a grandparent in common and you gradually Trace further and further back into the past adding these ever more distant relationships but eventually no matter how good you are at digging up the Church records and all that stuff you hit what the genealogists call a brick wall a point Beyond which you don't know anything else about your ancestors and you enter this dark and mysterious realm we call history that we have to feel our way through with whispered guidance who were these people who came before we have no written record well actually we do written in our DNA in our genetic code we have a historical document that takes us back in time to the very earliest days of our species and that's what we study now a quick primer on DNA I suspect that not everybody in the audience is a geneticist it is a very long linear molecule a coded version of how to make another copy of you it's your blueprint it's composed of four subunits a c g and T we call them and it's the sequence of those subunits that that defines that blueprint how long is it well it's billions of these subunits in length a hloy genome we actually have two copies of all of our chromosomes Hy genome is around 3.2 billion nucleotides in length and the whole thing if you add it all together it's over 6 billion nucleotides long if you take all the DNA out of one cell in your body and stretch it end to end it's around 2 m long if you take all the DNA out of every cell in your body and you stretch it end to end it would reach from here to the moon and back thousands of times it's a lot of information and so when you're copying this DNA molecule to pass it on it's a pretty tough job imagine the longest book you can think of war in peace and now multiply it by 100 and and imagine copying that by hand and you're working away until late at night and you're very very careful you're drinking coffee and you're paying attention but occasionally when you're copying this by hand you're going to make a little typo a spelling mistake substitute an i for an e or a c for a t same thing happens to our DNA as it's being passed on through the generations it doesn't happen very often we have a proof reading mechanism built in but when it does happen and these changes get transmitted down through the generations they become markers of descent if you share a marker with someone it means you share an ancestor at some point in the past the person who first had that change in their DNA and it's by looking at the pattern of genetic variation the pattern of these markers in people all over the world and assessing the relative ages when they occurred throughout our history that we've been able to construct a family tree for everybody alive today these are two pieces of DNA that we use quite widely in our work mitochondrial DNA tracing a purely maternal line of descent you get your mtdna from your mother and your mother's mother all the way back to the very first woman the Y chrom the piece of DNA that makes men men traces a purely patronal line of descent everybody in this room everybody in the world falls into a lineage somewhere on these trees now even though these are simplified versions of the real trees they're still kind of complicated so let's simplify them turn them on their sides combine them so that they look like a tree with the root at the bottom and the branches going up what's the Tome message well the thing that jumps out at you first is that the deepest lineages in our family trees are found within Africa among Africans that means that Africans have been accumulating this mutational diversity for longer and what that means is that we originated in Africa it's written in our DNA every piece of DNA we look at has greater diversity within Africa than outside of Africa and at some point in the past a subgroup of Africans left the African continent to go out and populate the rest of the world now how recently do we share this ancestry was it millions of years ago which we might suspect by looking at all this incredible variation around the world no the DNA tells a story that's very clear within the last 200,000 years we all share an ancestor a single person mitochondrial eve you might have heard about her in Africa an African woman who gave rise to all the mitochondrial diversity in the world today but what's even more amazing is that if you look at the Y chromosome side the male side of the story The Y chromosome Adam only lived around 60,000 years ago that's only about 2,000 human Generations the blink of an eye in an evolutionary sense that tells us we were all still living in Africa at that time this was an African man who gave rise to all the white chromosome diversity around the world it's only within the last 60,000 years that we have started to generate this incredible diversity we see around the world such an amazing story we're all effectively part of an extended African family now that seems so recent why didn't we start to leave earlier why didn't Homo erectus evolve into separate species or subspecies rather human races around the world why was it that we we seem to have come out of Africa so recently well that's a that's a big question these why questions particularly in genetics and the study of history in general are always the big ones the ones that are tough to answer and so when all else fails talk about the weather what was going on to the world's weather around 60,000 years ago well we were going into the worst part of the last ice age last ice age started roughly 120,000 years ago it went up and down and it really started to accelerate around 70,000 years ago lots of evidence from sediment cores and the pollen types oxygen Isotopes and so on we had the last glacial maximum around 16,000 years ago but basically from 70,000 years on things were getting really tough getting very cold the Northern Hemisphere had massive growing ice sheets New York City Chicago Seattle all under a sheet of ice most of Britain all of Scandinavia covered by Ice several kilometers thick now Africa is the most tropical continent on the planet about 85% of it lies between Cancer and Capricorn and there aren't a lot of glaciers here except on the high mountains here in East Africa so what was going on here we weren't covered in ice in Africa rather Africa was drying out at that time this is a paleoclimatological map of what Africa looked like between 60 and 70,000 years ago reconstructed from all these pieces of evidence that I mentioned before the reason for that is that ice actually sucks moisture out of the atmosphere if you think about Antarctica it's technically a desert it gets so little precipitation so the whole world was drying out the sea levels were dropping and Africa was turning to Desert the Sahara was much bigger then than it is now and the Human Habitat was reduced to just a few small Pockets compared to what we have today the evidence from genetic data is that the human population around this time roughly 7,000 years ago crashed to fewer than 2,000 individuals we nearly went extinct we were hanging on by our fingernails and then something happened great illustration of it look at some stone tools the ones on the left are from Africa from around a million years ago the ones on the right were made by neander tals our distant cousins not our direct ancestors living in Europe and they date from around 50 or 60,000 years ago now the the risk of offending any paleoanthropologists or physical Anthropologist in the audience basically there's not a lot of change between these two Stone tool groups ones on the left are pretty similar to the ones on the right we are in a period of long cultural stasis from a million years ago until around 60 to 70,000 years ago the tool Styles don't change that much the evidence is that the human way of life didn't change that much during that period but then 50 60 70,000 years ago somewhere in that region all hell breaks loose art makes its appearance the stone tools become much more finely crafted the evidence is that humans begin to specialize in particular prey spe species at particular times of the year the population size started to expand probably according to what many linguists believe fully modern language syntactic language subject verb object that we used to convey complex ideas like I'm doing now appeared around that time we became much more social the social networks expanded this change in Behavior allowed us to survive these worsening conditions in Africa and they allowed us to start to expand around the world we've been talking at this conference about African success stories well you want the ultimate African success story look in the mirror you're it the reason you're alive today is because of those changes in our brains that took place in Africa probably somewhere in the region where we're sitting right now around 60 70,000 years ago allowing us not only to survive in Africa but to expand Out of Africa an early Coastal migration along the south coast of Asia leaving Africa around 60,000 years ago reaching Australia very rapidly by 50,000 years ago slightly later migration up into the Middle East these would have been Savannah Hunters so those of you who are going on one of the the post-conference tours you'll get to see what a real Savannah is like and it's basically a meat locker people who would have specialized in killing the animals hunting the animals on those Meat Locker savanas moving up following the grasslands into the Middle East around 45,000 years ago during one of the the rare wet phases in the Sahara migrating Eastward following the grasslands because that's what they were adapted to live on and when they reached Central Asia they reached what was effectively a step Super Highway a grassland Super Highway the grasslands at that time this is during the last ice age stretched basically from Germany all the way over to Korea and the entire continent was open to them entering Europe around 35,000 years ago and finally a small group migrating up through the worst weather imaginable Siberia inside the Arctic Circle during the last ice age temperatures of -70 - 80 even- 100 perhaps migrating into the Americas ultimately reaching that final frontier an amazing story and it happened first in Africa the changes that allowed us to do that the evolution of this highly adaptable brain that we all carry around with us allowing us to create novel cultures allowing us to develop the diversity that we see on a whirlwind trip like the one I've just been on now that story I just told you is literally a whirlwind tour of how we populated the world the great Paleolithic wanderings of our species and that's the story that I told a couple of years ago in my book The Journey of man and the film that we made the same title and as we were finishing up that film it was co-produced with National Geographic I started talking to the folks at at NG about this work and they got really excited about it they you know they like the film but they said you know we really see this as kind of the next wave in the study of human Origins where we all came from using the tools of DNA to uh map the migrations around the world you know study of human Origins is kind of in our DNA and we want to take it to the next level what do you want to do next which is a great question to be asked by National Geographic and I said well you know what I've sketched out here is just that it is a very coarse sketch of how we migrated around the planet and it's based on a few thousand people we've sampled from you know a handful of populations around the world studied a few genetic markers and there are lots of gaps on this map we've just connected the dots what we need to do is increase our sample size by an order of magnitude or more hundreds of thousands of DNA samples from people all over the world and that was the Genesis of the genographic project the project launched in uh April of 2005 it has three core components obviously science is a big part of it the field research that we're doing around the world with indigenous peoples people who've lived in the same location for a long period of time retain a connection to the place where they live that many of the rest of us have lost so my ancestors come from all over northern Europe I live in the Eastern Seaboard of North America when I'm not traveling where am I indigenous to Nowhere really my jeans are all jumbled up but there are people who retain that link to their ancestors that allows us to contextualize the DNA results that's the focus of the field research centers that we've set up all over the world 10 of them top population geneticist but in addition we wanted to open up this study to anybody around the world how often do you get to participate in a big scientific project the Human Genome Project or a Mars rover mission in this case you actually can you can go onto our website nationalgeographic.com genographic you can order a kit you can test your own DNA and you can actually submit those results to the database and tell us a little bit about your genealogical background have the data analyzed as part of the scientific effort now this is all a nonprofit Enterprise and so the money that we raise after we cover the cost of doing the testing and making the kit components gets plowed back into the project the majority going to something we call the Legacy fund it's a charitable entity basically a grant-giving entity that gives money back to indigenous groups around the world for educational cultural projects initiated by them they apply to this Fund in order to do various projects and I'll show you a couple of examples so how are we doing in the project we've got about 25,000 samples collected from indigenous people around the world the most amazing thing has been the interest on the part of the public 210,000 people have ordered these participation kits since we launched two years ago which has raised around $5 million the majority of which at least half is going back into the Legacy fund we've just awarded the First Legacy grants totaling around $500,000 projects around the world documenting oral poetry and CER preserving traditional weaving patterns in Gaza language revitalization in Tajikistan etc etc so the project is going very very well and I urge you to check out the website and watch this space thank you very [Applause] much

Channel: Idk

Views: 7,601

Keywords: Spencer, Wells, TED, 2007, mapa, genetico, arbol, genealogico, ADN, aminoacidos, ancestros, comunes, poblacion, descendencia, africa, primates, especies, darwin, cultura, neandertales, historia, de, la, humanidad, español, subtitulado, sub, esp

Id: swlykLMrR5o

Length: 20min 52sec (1252 seconds)

Published: Fri Dec 23 2011