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Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:03.00,Default,,0000,0000,0000,,What I want to talk to you about
Dialogue: 0,0:00:03.00,0:00:05.00,Default,,0000,0000,0000,,is what we can learn from studying the genomes
Dialogue: 0,0:00:05.00,0:00:07.00,Default,,0000,0000,0000,,of living people
Dialogue: 0,0:00:07.00,0:00:09.00,Default,,0000,0000,0000,,and extinct humans.
Dialogue: 0,0:00:09.00,0:00:11.00,Default,,0000,0000,0000,,But before doing that,
Dialogue: 0,0:00:11.00,0:00:14.00,Default,,0000,0000,0000,,I just briefly want to remind you about what you already know:
Dialogue: 0,0:00:14.00,0:00:16.00,Default,,0000,0000,0000,,that our genomes, our genetic material,
Dialogue: 0,0:00:16.00,0:00:19.00,Default,,0000,0000,0000,,are stored in almost all cells in our bodies in chromosomes
Dialogue: 0,0:00:19.00,0:00:21.00,Default,,0000,0000,0000,,in the form of DNA,
Dialogue: 0,0:00:21.00,0:00:24.00,Default,,0000,0000,0000,,which is this famous double-helical molecule.
Dialogue: 0,0:00:24.00,0:00:26.00,Default,,0000,0000,0000,,And the genetic information
Dialogue: 0,0:00:26.00,0:00:28.00,Default,,0000,0000,0000,,is contained in the form of a sequence
Dialogue: 0,0:00:28.00,0:00:30.00,Default,,0000,0000,0000,,of four bases
Dialogue: 0,0:00:30.00,0:00:33.00,Default,,0000,0000,0000,,abbreviated with the letters A, T, C and G.
Dialogue: 0,0:00:33.00,0:00:35.00,Default,,0000,0000,0000,,And the information is there twice --
Dialogue: 0,0:00:35.00,0:00:37.00,Default,,0000,0000,0000,,one on each strand --
Dialogue: 0,0:00:37.00,0:00:39.00,Default,,0000,0000,0000,,which is important,
Dialogue: 0,0:00:39.00,0:00:41.00,Default,,0000,0000,0000,,because when new cells are formed, these strands come apart,
Dialogue: 0,0:00:41.00,0:00:44.00,Default,,0000,0000,0000,,new strands are synthesized with the old ones as templates
Dialogue: 0,0:00:44.00,0:00:47.00,Default,,0000,0000,0000,,in an almost perfect process.
Dialogue: 0,0:00:47.00,0:00:49.00,Default,,0000,0000,0000,,But nothing, of course, in nature
Dialogue: 0,0:00:49.00,0:00:51.00,Default,,0000,0000,0000,,is totally perfect,
Dialogue: 0,0:00:51.00,0:00:53.00,Default,,0000,0000,0000,,so sometimes an error is made
Dialogue: 0,0:00:53.00,0:00:56.00,Default,,0000,0000,0000,,and a wrong letter is built in.
Dialogue: 0,0:00:56.00,0:00:58.00,Default,,0000,0000,0000,,And we can then see the result
Dialogue: 0,0:00:58.00,0:01:00.00,Default,,0000,0000,0000,,of such mutations
Dialogue: 0,0:01:00.00,0:01:02.00,Default,,0000,0000,0000,,when we compare DNA sequences
Dialogue: 0,0:01:02.00,0:01:05.00,Default,,0000,0000,0000,,among us here in the room, for example.
Dialogue: 0,0:01:05.00,0:01:08.00,Default,,0000,0000,0000,,If we compare my genome to the genome of you,
Dialogue: 0,0:01:08.00,0:01:12.00,Default,,0000,0000,0000,,approximately every 1,200, 1,300 letters
Dialogue: 0,0:01:12.00,0:01:14.00,Default,,0000,0000,0000,,will differ between us.
Dialogue: 0,0:01:14.00,0:01:16.00,Default,,0000,0000,0000,,And these mutations accumulate
Dialogue: 0,0:01:16.00,0:01:19.00,Default,,0000,0000,0000,,approximately as a function of time.
Dialogue: 0,0:01:19.00,0:01:22.00,Default,,0000,0000,0000,,So if we add in a chimpanzee here, we will see more differences.
Dialogue: 0,0:01:22.00,0:01:25.00,Default,,0000,0000,0000,,Approximately one letter in a hundred
Dialogue: 0,0:01:25.00,0:01:27.00,Default,,0000,0000,0000,,will differ from a chimpanzee.
Dialogue: 0,0:01:27.00,0:01:29.00,Default,,0000,0000,0000,,And if you're then interested in the history
Dialogue: 0,0:01:29.00,0:01:31.00,Default,,0000,0000,0000,,of a piece of DNA, or the whole genome,
Dialogue: 0,0:01:31.00,0:01:34.00,Default,,0000,0000,0000,,you can reconstruct the history of the DNA
Dialogue: 0,0:01:34.00,0:01:36.00,Default,,0000,0000,0000,,with those differences you observe.
Dialogue: 0,0:01:36.00,0:01:40.00,Default,,0000,0000,0000,,And generally we depict our ideas about this history
Dialogue: 0,0:01:40.00,0:01:42.00,Default,,0000,0000,0000,,in the form of trees like this.
Dialogue: 0,0:01:42.00,0:01:44.00,Default,,0000,0000,0000,,In this case, it's very simple.
Dialogue: 0,0:01:44.00,0:01:46.00,Default,,0000,0000,0000,,The two human DNA sequences
Dialogue: 0,0:01:46.00,0:01:49.00,Default,,0000,0000,0000,,go back to a common ancestor quite recently.
Dialogue: 0,0:01:49.00,0:01:53.00,Default,,0000,0000,0000,,Farther back is there one shared with chimpanzees.
Dialogue: 0,0:01:53.00,0:01:56.00,Default,,0000,0000,0000,,And because these mutations
Dialogue: 0,0:01:56.00,0:01:58.00,Default,,0000,0000,0000,,happen approximately as a function of time,
Dialogue: 0,0:01:58.00,0:02:00.00,Default,,0000,0000,0000,,you can transform these differences
Dialogue: 0,0:02:00.00,0:02:02.00,Default,,0000,0000,0000,,to estimates of time,
Dialogue: 0,0:02:02.00,0:02:04.00,Default,,0000,0000,0000,,where the two humans, typically,
Dialogue: 0,0:02:04.00,0:02:08.00,Default,,0000,0000,0000,,will share a common ancestor about half a million years ago,
Dialogue: 0,0:02:08.00,0:02:10.00,Default,,0000,0000,0000,,and with the chimpanzees,
Dialogue: 0,0:02:10.00,0:02:13.00,Default,,0000,0000,0000,,it will be in the order of five million years ago.
Dialogue: 0,0:02:13.00,0:02:15.00,Default,,0000,0000,0000,,So what has now happened in the last few years
Dialogue: 0,0:02:15.00,0:02:17.00,Default,,0000,0000,0000,,is that there are account technologies around
Dialogue: 0,0:02:17.00,0:02:21.00,Default,,0000,0000,0000,,that allow you to see many, many pieces of DNA very quickly.
Dialogue: 0,0:02:21.00,0:02:23.00,Default,,0000,0000,0000,,So we can now, in a matter of hours,
Dialogue: 0,0:02:23.00,0:02:26.00,Default,,0000,0000,0000,,determine a whole human genome.
Dialogue: 0,0:02:26.00,0:02:29.00,Default,,0000,0000,0000,,Each of us, of course, contains two human genomes --
Dialogue: 0,0:02:29.00,0:02:32.00,Default,,0000,0000,0000,,one from our mothers and one from our fathers.
Dialogue: 0,0:02:32.00,0:02:36.00,Default,,0000,0000,0000,,And they are around three billion such letters long.
Dialogue: 0,0:02:36.00,0:02:38.00,Default,,0000,0000,0000,,And we will find that the two genomes in me,
Dialogue: 0,0:02:38.00,0:02:40.00,Default,,0000,0000,0000,,or one genome of mine we want to use,
Dialogue: 0,0:02:40.00,0:02:43.00,Default,,0000,0000,0000,,will have about three million differences
Dialogue: 0,0:02:43.00,0:02:45.00,Default,,0000,0000,0000,,in the order of that.
Dialogue: 0,0:02:45.00,0:02:47.00,Default,,0000,0000,0000,,And what you can then also begin to do
Dialogue: 0,0:02:47.00,0:02:49.00,Default,,0000,0000,0000,,is to say, "How are these genetic differences
Dialogue: 0,0:02:49.00,0:02:51.00,Default,,0000,0000,0000,,distributed across the world?"
Dialogue: 0,0:02:51.00,0:02:53.00,Default,,0000,0000,0000,,And if you do that,
Dialogue: 0,0:02:53.00,0:02:57.00,Default,,0000,0000,0000,,you find a certain amount of genetic variation in Africa.
Dialogue: 0,0:02:57.00,0:03:00.00,Default,,0000,0000,0000,,And if you look outside Africa,
Dialogue: 0,0:03:00.00,0:03:03.00,Default,,0000,0000,0000,,you actually find less genetic variation.
Dialogue: 0,0:03:03.00,0:03:05.00,Default,,0000,0000,0000,,This is surprising, of course,
Dialogue: 0,0:03:05.00,0:03:08.00,Default,,0000,0000,0000,,because in the order of six to eight times fewer people
Dialogue: 0,0:03:08.00,0:03:11.00,Default,,0000,0000,0000,,live in Africa than outside Africa.
Dialogue: 0,0:03:11.00,0:03:14.00,Default,,0000,0000,0000,,Yet the people inside Africa
Dialogue: 0,0:03:14.00,0:03:17.00,Default,,0000,0000,0000,,have more genetic variation.
Dialogue: 0,0:03:17.00,0:03:19.00,Default,,0000,0000,0000,,Moreover, almost all these genetic variants
Dialogue: 0,0:03:19.00,0:03:21.00,Default,,0000,0000,0000,,we see outside Africa
Dialogue: 0,0:03:21.00,0:03:23.00,Default,,0000,0000,0000,,have closely related DNA sequences
Dialogue: 0,0:03:23.00,0:03:25.00,Default,,0000,0000,0000,,that you find inside Africa.
Dialogue: 0,0:03:25.00,0:03:27.00,Default,,0000,0000,0000,,But if you look in Africa,
Dialogue: 0,0:03:27.00,0:03:30.00,Default,,0000,0000,0000,,there is a component of the genetic variation
Dialogue: 0,0:03:30.00,0:03:33.00,Default,,0000,0000,0000,,that has no close relatives outside.
Dialogue: 0,0:03:33.00,0:03:36.00,Default,,0000,0000,0000,,So a model to explain this
Dialogue: 0,0:03:36.00,0:03:39.00,Default,,0000,0000,0000,,is that a part of the African variation, but not all of it,
Dialogue: 0,0:03:39.00,0:03:43.00,Default,,0000,0000,0000,,[has] gone out and colonized the rest of the world.
Dialogue: 0,0:03:43.00,0:03:47.00,Default,,0000,0000,0000,,And together with the methods to date these genetic differences,
Dialogue: 0,0:03:47.00,0:03:49.00,Default,,0000,0000,0000,,this has led to the insight
Dialogue: 0,0:03:49.00,0:03:51.00,Default,,0000,0000,0000,,that modern humans --
Dialogue: 0,0:03:51.00,0:03:54.00,Default,,0000,0000,0000,,humans that are essentially indistinguishable from you and me --
Dialogue: 0,0:03:54.00,0:03:57.00,Default,,0000,0000,0000,,evolved in Africa, quite recently,
Dialogue: 0,0:03:57.00,0:04:01.00,Default,,0000,0000,0000,,between 100 and 200,000 years ago.
Dialogue: 0,0:04:01.00,0:04:05.00,Default,,0000,0000,0000,,And later, between 100 and 50,000 years ago or so,
Dialogue: 0,0:04:05.00,0:04:07.00,Default,,0000,0000,0000,,went out of Africa
Dialogue: 0,0:04:07.00,0:04:09.00,Default,,0000,0000,0000,,to colonize the rest of the world.
Dialogue: 0,0:04:09.00,0:04:11.00,Default,,0000,0000,0000,,So what I often like to say
Dialogue: 0,0:04:11.00,0:04:13.00,Default,,0000,0000,0000,,is that, from a genomic perspective,
Dialogue: 0,0:04:13.00,0:04:15.00,Default,,0000,0000,0000,,we are all Africans.
Dialogue: 0,0:04:15.00,0:04:18.00,Default,,0000,0000,0000,,We either live inside Africa today,
Dialogue: 0,0:04:18.00,0:04:20.00,Default,,0000,0000,0000,,or in quite recent exile.
Dialogue: 0,0:04:20.00,0:04:22.00,Default,,0000,0000,0000,,Another consequence
Dialogue: 0,0:04:22.00,0:04:25.00,Default,,0000,0000,0000,,of this recent origin of modern humans
Dialogue: 0,0:04:25.00,0:04:27.00,Default,,0000,0000,0000,,is that genetic variants
Dialogue: 0,0:04:27.00,0:04:29.00,Default,,0000,0000,0000,,are generally distributed widely in the world,
Dialogue: 0,0:04:29.00,0:04:31.00,Default,,0000,0000,0000,,in many places,
Dialogue: 0,0:04:31.00,0:04:34.00,Default,,0000,0000,0000,,and they tend to vary as gradients,
Dialogue: 0,0:04:34.00,0:04:38.00,Default,,0000,0000,0000,,from a bird's-eye perspective at least.
Dialogue: 0,0:04:38.00,0:04:40.00,Default,,0000,0000,0000,,And since there are many genetic variants,
Dialogue: 0,0:04:40.00,0:04:43.00,Default,,0000,0000,0000,,and they have different such gradients,
Dialogue: 0,0:04:43.00,0:04:46.00,Default,,0000,0000,0000,,this means that if we determine a DNA sequence --
Dialogue: 0,0:04:46.00,0:04:49.00,Default,,0000,0000,0000,,a genome from one individual --
Dialogue: 0,0:04:49.00,0:04:51.00,Default,,0000,0000,0000,,we can quite accurately estimate
Dialogue: 0,0:04:51.00,0:04:53.00,Default,,0000,0000,0000,,where that person comes from,
Dialogue: 0,0:04:53.00,0:04:55.00,Default,,0000,0000,0000,,provided that its parents or grandparents
Dialogue: 0,0:04:55.00,0:04:58.00,Default,,0000,0000,0000,,haven't moved around too much.
Dialogue: 0,0:04:58.00,0:05:00.00,Default,,0000,0000,0000,,But does this then mean,
Dialogue: 0,0:05:00.00,0:05:02.00,Default,,0000,0000,0000,,as many people tend to think,
Dialogue: 0,0:05:02.00,0:05:05.00,Default,,0000,0000,0000,,that there are huge genetic differences between groups of people --
Dialogue: 0,0:05:05.00,0:05:07.00,Default,,0000,0000,0000,,on different continents, for example?
Dialogue: 0,0:05:07.00,0:05:10.00,Default,,0000,0000,0000,,Well we can begin to ask those questions also.
Dialogue: 0,0:05:10.00,0:05:13.00,Default,,0000,0000,0000,,There is, for example, a project that's underway
Dialogue: 0,0:05:13.00,0:05:15.00,Default,,0000,0000,0000,,to sequence a thousand individuals --
Dialogue: 0,0:05:15.00,0:05:18.00,Default,,0000,0000,0000,,their genomes -- from different parts of the world.
Dialogue: 0,0:05:18.00,0:05:21.00,Default,,0000,0000,0000,,They've sequenced 185 Africans
Dialogue: 0,0:05:21.00,0:05:24.00,Default,,0000,0000,0000,,from two populations in Africa.
Dialogue: 0,0:05:24.00,0:05:27.00,Default,,0000,0000,0000,,[They've] sequenced approximately equally [as] many people
Dialogue: 0,0:05:27.00,0:05:30.00,Default,,0000,0000,0000,,in Europe and in China.
Dialogue: 0,0:05:30.00,0:05:33.00,Default,,0000,0000,0000,,And we can begin to say how much variance do we find,
Dialogue: 0,0:05:33.00,0:05:36.00,Default,,0000,0000,0000,,how many letters that vary
Dialogue: 0,0:05:36.00,0:05:39.00,Default,,0000,0000,0000,,in at least one of those individual sequences.
Dialogue: 0,0:05:39.00,0:05:43.00,Default,,0000,0000,0000,,And it's a lot: 38 million variable positions.
Dialogue: 0,0:05:43.00,0:05:46.00,Default,,0000,0000,0000,,But we can then ask: Are there any absolute differences
Dialogue: 0,0:05:46.00,0:05:48.00,Default,,0000,0000,0000,,between Africans and non-Africans?
Dialogue: 0,0:05:48.00,0:05:50.00,Default,,0000,0000,0000,,Perhaps the biggest difference
Dialogue: 0,0:05:50.00,0:05:52.00,Default,,0000,0000,0000,,most of us would imagine existed.
Dialogue: 0,0:05:52.00,0:05:54.00,Default,,0000,0000,0000,,And with absolute difference --
Dialogue: 0,0:05:54.00,0:05:56.00,Default,,0000,0000,0000,,and I mean a difference
Dialogue: 0,0:05:56.00,0:05:59.00,Default,,0000,0000,0000,,where people inside Africa at a certain position,
Dialogue: 0,0:05:59.00,0:06:02.00,Default,,0000,0000,0000,,where all individuals -- 100 percent -- have one letter,
Dialogue: 0,0:06:02.00,0:06:06.00,Default,,0000,0000,0000,,and everybody outside Africa has another letter.
Dialogue: 0,0:06:06.00,0:06:09.00,Default,,0000,0000,0000,,And the answer to that, among those millions of differences,
Dialogue: 0,0:06:09.00,0:06:12.00,Default,,0000,0000,0000,,is that there is not a single such position.
Dialogue: 0,0:06:14.00,0:06:16.00,Default,,0000,0000,0000,,This may be surprising.
Dialogue: 0,0:06:16.00,0:06:19.00,Default,,0000,0000,0000,,Maybe a single individual is misclassified or so.
Dialogue: 0,0:06:19.00,0:06:21.00,Default,,0000,0000,0000,,So we can relax the criterion a bit
Dialogue: 0,0:06:21.00,0:06:23.00,Default,,0000,0000,0000,,and say: How many positions do we find
Dialogue: 0,0:06:23.00,0:06:25.00,Default,,0000,0000,0000,,where 95 percent of people in Africa have
Dialogue: 0,0:06:25.00,0:06:27.00,Default,,0000,0000,0000,,one variant,
Dialogue: 0,0:06:27.00,0:06:29.00,Default,,0000,0000,0000,,95 percent another variant,
Dialogue: 0,0:06:29.00,0:06:31.00,Default,,0000,0000,0000,,and the number of that is 12.
Dialogue: 0,0:06:31.00,0:06:33.00,Default,,0000,0000,0000,,So this is very surprising.
Dialogue: 0,0:06:33.00,0:06:35.00,Default,,0000,0000,0000,,It means that when we look at people
Dialogue: 0,0:06:35.00,0:06:38.00,Default,,0000,0000,0000,,and see a person from Africa
Dialogue: 0,0:06:38.00,0:06:41.00,Default,,0000,0000,0000,,and a person from Europe or Asia,
Dialogue: 0,0:06:41.00,0:06:45.00,Default,,0000,0000,0000,,we cannot, for a single position in the genome with 100 percent accuracy,
Dialogue: 0,0:06:45.00,0:06:47.00,Default,,0000,0000,0000,,predict what the person would carry.
Dialogue: 0,0:06:47.00,0:06:49.00,Default,,0000,0000,0000,,And only for 12 positions
Dialogue: 0,0:06:49.00,0:06:53.00,Default,,0000,0000,0000,,can we hope to be 95 percent right.
Dialogue: 0,0:06:53.00,0:06:55.00,Default,,0000,0000,0000,,This may be surprising,
Dialogue: 0,0:06:55.00,0:06:57.00,Default,,0000,0000,0000,,because we can, of course, look at these people
Dialogue: 0,0:06:57.00,0:07:01.00,Default,,0000,0000,0000,,and quite easily say where they or their ancestors came from.
Dialogue: 0,0:07:01.00,0:07:03.00,Default,,0000,0000,0000,,So what this means now
Dialogue: 0,0:07:03.00,0:07:05.00,Default,,0000,0000,0000,,is that those traits we then look at
Dialogue: 0,0:07:05.00,0:07:07.00,Default,,0000,0000,0000,,and so readily see --
Dialogue: 0,0:07:07.00,0:07:10.00,Default,,0000,0000,0000,,facial features, skin color, hair structure --
Dialogue: 0,0:07:10.00,0:07:14.00,Default,,0000,0000,0000,,are not determined by single genes with big effects,
Dialogue: 0,0:07:14.00,0:07:17.00,Default,,0000,0000,0000,,but are determined by many different genetic variants
Dialogue: 0,0:07:17.00,0:07:19.00,Default,,0000,0000,0000,,that seem to vary in frequency
Dialogue: 0,0:07:19.00,0:07:21.00,Default,,0000,0000,0000,,between different parts of the world.
Dialogue: 0,0:07:21.00,0:07:24.00,Default,,0000,0000,0000,,There is another thing with those traits
Dialogue: 0,0:07:24.00,0:07:27.00,Default,,0000,0000,0000,,that we so easily observe in each other
Dialogue: 0,0:07:27.00,0:07:29.00,Default,,0000,0000,0000,,that I think is worthwhile to consider,
Dialogue: 0,0:07:29.00,0:07:32.00,Default,,0000,0000,0000,,and that is that, in a very literal sense,
Dialogue: 0,0:07:32.00,0:07:35.00,Default,,0000,0000,0000,,they're really on the surface of our bodies.
Dialogue: 0,0:07:35.00,0:07:37.00,Default,,0000,0000,0000,,They are what we just said --
Dialogue: 0,0:07:37.00,0:07:40.00,Default,,0000,0000,0000,,facial features, hair structure, skin color.
Dialogue: 0,0:07:40.00,0:07:42.00,Default,,0000,0000,0000,,There are also a number of features
Dialogue: 0,0:07:42.00,0:07:44.00,Default,,0000,0000,0000,,that vary between continents like that
Dialogue: 0,0:07:44.00,0:07:48.00,Default,,0000,0000,0000,,that have to do with how we metabolize food that we ingest,
Dialogue: 0,0:07:48.00,0:07:50.00,Default,,0000,0000,0000,,or that have to do
Dialogue: 0,0:07:50.00,0:07:53.00,Default,,0000,0000,0000,,with how our immune systems deal with microbes
Dialogue: 0,0:07:53.00,0:07:55.00,Default,,0000,0000,0000,,that try to invade our bodies.
Dialogue: 0,0:07:55.00,0:07:57.00,Default,,0000,0000,0000,,But so those are all parts of our bodies
Dialogue: 0,0:07:57.00,0:08:00.00,Default,,0000,0000,0000,,where we very directly interact with our environment,
Dialogue: 0,0:08:00.00,0:08:04.00,Default,,0000,0000,0000,,in a direct confrontation, if you like.
Dialogue: 0,0:08:04.00,0:08:06.00,Default,,0000,0000,0000,,It's easy to imagine
Dialogue: 0,0:08:06.00,0:08:08.00,Default,,0000,0000,0000,,how particularly those parts of our bodies
Dialogue: 0,0:08:08.00,0:08:11.00,Default,,0000,0000,0000,,were quickly influenced by selection from the environment
Dialogue: 0,0:08:11.00,0:08:13.00,Default,,0000,0000,0000,,and shifted frequencies of genes
Dialogue: 0,0:08:13.00,0:08:15.00,Default,,0000,0000,0000,,that are involved in them.
Dialogue: 0,0:08:15.00,0:08:18.00,Default,,0000,0000,0000,,But if we look on other parts of our bodies
Dialogue: 0,0:08:18.00,0:08:20.00,Default,,0000,0000,0000,,where we don't directly interact with the environment --
Dialogue: 0,0:08:20.00,0:08:23.00,Default,,0000,0000,0000,,our kidneys, our livers, our hearts --
Dialogue: 0,0:08:23.00,0:08:25.00,Default,,0000,0000,0000,,there is no way to say,
Dialogue: 0,0:08:25.00,0:08:27.00,Default,,0000,0000,0000,,by just looking at these organs,
Dialogue: 0,0:08:27.00,0:08:30.00,Default,,0000,0000,0000,,where in the world they would come from.
Dialogue: 0,0:08:31.00,0:08:33.00,Default,,0000,0000,0000,,So there's another interesting thing
Dialogue: 0,0:08:33.00,0:08:36.00,Default,,0000,0000,0000,,that comes from this realization
Dialogue: 0,0:08:36.00,0:08:40.00,Default,,0000,0000,0000,,that humans have a recent common origin in Africa,
Dialogue: 0,0:08:40.00,0:08:43.00,Default,,0000,0000,0000,,and that is that when those humans emerged
Dialogue: 0,0:08:43.00,0:08:45.00,Default,,0000,0000,0000,,around 100,000 years ago or so,
Dialogue: 0,0:08:45.00,0:08:47.00,Default,,0000,0000,0000,,they were not alone on the planet.
Dialogue: 0,0:08:47.00,0:08:50.00,Default,,0000,0000,0000,,There were other forms of humans around,
Dialogue: 0,0:08:50.00,0:08:53.00,Default,,0000,0000,0000,,most famously perhaps, Neanderthals --
Dialogue: 0,0:08:53.00,0:08:55.00,Default,,0000,0000,0000,,these robust forms of humans,
Dialogue: 0,0:08:55.00,0:08:57.00,Default,,0000,0000,0000,,compared to the left here
Dialogue: 0,0:08:57.00,0:09:01.00,Default,,0000,0000,0000,,with a modern human skeleton on the right --
Dialogue: 0,0:09:01.00,0:09:04.00,Default,,0000,0000,0000,,that existed in Western Asia and Europe
Dialogue: 0,0:09:04.00,0:09:06.00,Default,,0000,0000,0000,,since several hundreds of thousands of years.
Dialogue: 0,0:09:06.00,0:09:08.00,Default,,0000,0000,0000,,So an interesting question is,
Dialogue: 0,0:09:08.00,0:09:10.00,Default,,0000,0000,0000,,what happened when we met?
Dialogue: 0,0:09:10.00,0:09:12.00,Default,,0000,0000,0000,,What happened to the Neanderthals?
Dialogue: 0,0:09:12.00,0:09:14.00,Default,,0000,0000,0000,,And to begin to answer such questions,
Dialogue: 0,0:09:14.00,0:09:18.00,Default,,0000,0000,0000,,my research group -- since over 25 years now --
Dialogue: 0,0:09:18.00,0:09:20.00,Default,,0000,0000,0000,,works on methods to extract DNA
Dialogue: 0,0:09:20.00,0:09:22.00,Default,,0000,0000,0000,,from remains of Neanderthals
Dialogue: 0,0:09:22.00,0:09:24.00,Default,,0000,0000,0000,,and extinct animals
Dialogue: 0,0:09:24.00,0:09:27.00,Default,,0000,0000,0000,,that are tens of thousands of years old.
Dialogue: 0,0:09:27.00,0:09:30.00,Default,,0000,0000,0000,,So this involves a lot of technical issues
Dialogue: 0,0:09:30.00,0:09:32.00,Default,,0000,0000,0000,,in how you extract the DNA,
Dialogue: 0,0:09:32.00,0:09:35.00,Default,,0000,0000,0000,,how you convert it to a form you can sequence.
Dialogue: 0,0:09:35.00,0:09:37.00,Default,,0000,0000,0000,,You have to work very carefully
Dialogue: 0,0:09:37.00,0:09:40.00,Default,,0000,0000,0000,,to avoid contamination of experiments
Dialogue: 0,0:09:40.00,0:09:43.00,Default,,0000,0000,0000,,with DNA from yourself.
Dialogue: 0,0:09:43.00,0:09:46.00,Default,,0000,0000,0000,,And this then, in conjunction with these methods
Dialogue: 0,0:09:46.00,0:09:50.00,Default,,0000,0000,0000,,that allow very many DNA molecules to be sequenced very rapidly,
Dialogue: 0,0:09:50.00,0:09:52.00,Default,,0000,0000,0000,,allowed us last year
Dialogue: 0,0:09:52.00,0:09:55.00,Default,,0000,0000,0000,,to present the first version of the Neanderthal genome,
Dialogue: 0,0:09:55.00,0:09:57.00,Default,,0000,0000,0000,,so that any one of you
Dialogue: 0,0:09:57.00,0:09:59.00,Default,,0000,0000,0000,,can now look on the Internet, on the Neanderthal genome,
Dialogue: 0,0:09:59.00,0:10:02.00,Default,,0000,0000,0000,,or at least on the 55 percent of it
Dialogue: 0,0:10:02.00,0:10:05.00,Default,,0000,0000,0000,,that we've been able to reconstruct so far.
Dialogue: 0,0:10:05.00,0:10:07.00,Default,,0000,0000,0000,,And you can begin to compare it to the genomes
Dialogue: 0,0:10:07.00,0:10:10.00,Default,,0000,0000,0000,,of people who live today.
Dialogue: 0,0:10:10.00,0:10:12.00,Default,,0000,0000,0000,,And one question
Dialogue: 0,0:10:12.00,0:10:14.00,Default,,0000,0000,0000,,that you may then want to ask
Dialogue: 0,0:10:14.00,0:10:16.00,Default,,0000,0000,0000,,is, what happened when we met?
Dialogue: 0,0:10:16.00,0:10:18.00,Default,,0000,0000,0000,,Did we mix or not?
Dialogue: 0,0:10:18.00,0:10:20.00,Default,,0000,0000,0000,,And the way to ask that question
Dialogue: 0,0:10:20.00,0:10:23.00,Default,,0000,0000,0000,,is to look at the Neanderthal that comes from Southern Europe
Dialogue: 0,0:10:23.00,0:10:25.00,Default,,0000,0000,0000,,and compare it to genomes
Dialogue: 0,0:10:25.00,0:10:27.00,Default,,0000,0000,0000,,of people who live today.
Dialogue: 0,0:10:27.00,0:10:29.00,Default,,0000,0000,0000,,So we then look
Dialogue: 0,0:10:29.00,0:10:31.00,Default,,0000,0000,0000,,to do this with pairs of individuals,
Dialogue: 0,0:10:31.00,0:10:33.00,Default,,0000,0000,0000,,starting with two Africans,
Dialogue: 0,0:10:33.00,0:10:35.00,Default,,0000,0000,0000,,looking at the two African genomes,
Dialogue: 0,0:10:35.00,0:10:38.00,Default,,0000,0000,0000,,finding places where they differ from each other,
Dialogue: 0,0:10:38.00,0:10:41.00,Default,,0000,0000,0000,,and in each case ask: What is a Neanderthal like?
Dialogue: 0,0:10:41.00,0:10:44.00,Default,,0000,0000,0000,,Does it match one African or the other African?
Dialogue: 0,0:10:44.00,0:10:47.00,Default,,0000,0000,0000,,We would expect there to be no difference,
Dialogue: 0,0:10:47.00,0:10:49.00,Default,,0000,0000,0000,,because Neanderthals were never in Africa.
Dialogue: 0,0:10:49.00,0:10:52.00,Default,,0000,0000,0000,,They should be equal, have no reason to be closer
Dialogue: 0,0:10:52.00,0:10:55.00,Default,,0000,0000,0000,,to one African than another African.
Dialogue: 0,0:10:55.00,0:10:57.00,Default,,0000,0000,0000,,And that's indeed the case.
Dialogue: 0,0:10:57.00,0:10:59.00,Default,,0000,0000,0000,,Statistically speaking, there is no difference
Dialogue: 0,0:10:59.00,0:11:03.00,Default,,0000,0000,0000,,in how often the Neanderthal matches one African or the other.
Dialogue: 0,0:11:03.00,0:11:05.00,Default,,0000,0000,0000,,But this is different
Dialogue: 0,0:11:05.00,0:11:09.00,Default,,0000,0000,0000,,if we now look at the European individual and an African.
Dialogue: 0,0:11:09.00,0:11:12.00,Default,,0000,0000,0000,,Then, significantly more often,
Dialogue: 0,0:11:12.00,0:11:14.00,Default,,0000,0000,0000,,does a Neanderthal match the European
Dialogue: 0,0:11:14.00,0:11:16.00,Default,,0000,0000,0000,,rather than the African.
Dialogue: 0,0:11:16.00,0:11:19.00,Default,,0000,0000,0000,,The same is true if we look at a Chinese individual
Dialogue: 0,0:11:19.00,0:11:21.00,Default,,0000,0000,0000,,versus an African,
Dialogue: 0,0:11:21.00,0:11:25.00,Default,,0000,0000,0000,,the Neanderthal will match the Chinese individual more often.
Dialogue: 0,0:11:25.00,0:11:27.00,Default,,0000,0000,0000,,This may also be surprising
Dialogue: 0,0:11:27.00,0:11:29.00,Default,,0000,0000,0000,,because the Neanderthals were never in China.
Dialogue: 0,0:11:29.00,0:11:33.00,Default,,0000,0000,0000,,So the model we've proposed to explain this
Dialogue: 0,0:11:33.00,0:11:35.00,Default,,0000,0000,0000,,is that when modern humans came out of Africa
Dialogue: 0,0:11:35.00,0:11:38.00,Default,,0000,0000,0000,,sometime after 100,000 years ago,
Dialogue: 0,0:11:38.00,0:11:40.00,Default,,0000,0000,0000,,they met Neanderthals.
Dialogue: 0,0:11:40.00,0:11:43.00,Default,,0000,0000,0000,,Presumably, they did so first in the Middle East,
Dialogue: 0,0:11:43.00,0:11:45.00,Default,,0000,0000,0000,,where there were Neanderthals living.
Dialogue: 0,0:11:45.00,0:11:47.00,Default,,0000,0000,0000,,If they then mixed with each other there,
Dialogue: 0,0:11:47.00,0:11:49.00,Default,,0000,0000,0000,,then those modern humans
Dialogue: 0,0:11:49.00,0:11:51.00,Default,,0000,0000,0000,,that became the ancestors
Dialogue: 0,0:11:51.00,0:11:53.00,Default,,0000,0000,0000,,of everyone outside Africa
Dialogue: 0,0:11:53.00,0:11:56.00,Default,,0000,0000,0000,,carried with them this Neanderthal component in their genome
Dialogue: 0,0:11:56.00,0:11:58.00,Default,,0000,0000,0000,,to the rest of the world.
Dialogue: 0,0:11:58.00,0:12:01.00,Default,,0000,0000,0000,,So that today, the people living outside Africa
Dialogue: 0,0:12:01.00,0:12:04.00,Default,,0000,0000,0000,,have about two and a half percent of their DNA
Dialogue: 0,0:12:04.00,0:12:06.00,Default,,0000,0000,0000,,from Neanderthals.
Dialogue: 0,0:12:06.00,0:12:09.00,Default,,0000,0000,0000,,So having now a Neanderthal genome
Dialogue: 0,0:12:09.00,0:12:11.00,Default,,0000,0000,0000,,on hand as a reference point
Dialogue: 0,0:12:11.00,0:12:13.00,Default,,0000,0000,0000,,and having the technologies
Dialogue: 0,0:12:13.00,0:12:15.00,Default,,0000,0000,0000,,to look at ancient remains
Dialogue: 0,0:12:15.00,0:12:17.00,Default,,0000,0000,0000,,and extract the DNA,
Dialogue: 0,0:12:17.00,0:12:21.00,Default,,0000,0000,0000,,we can begin to apply them elsewhere in the world.
Dialogue: 0,0:12:21.00,0:12:24.00,Default,,0000,0000,0000,,And the first place we've done that is in Southern Siberia
Dialogue: 0,0:12:24.00,0:12:26.00,Default,,0000,0000,0000,,in the Altai Mountains
Dialogue: 0,0:12:26.00,0:12:28.00,Default,,0000,0000,0000,,at a place called Denisova,
Dialogue: 0,0:12:28.00,0:12:30.00,Default,,0000,0000,0000,,a cave site in this mountain here,
Dialogue: 0,0:12:30.00,0:12:33.00,Default,,0000,0000,0000,,where archeologists in 2008
Dialogue: 0,0:12:33.00,0:12:35.00,Default,,0000,0000,0000,,found a tiny little piece of bone --
Dialogue: 0,0:12:35.00,0:12:37.00,Default,,0000,0000,0000,,this is a copy of it --
Dialogue: 0,0:12:37.00,0:12:41.00,Default,,0000,0000,0000,,that they realized came from the last phalanx
Dialogue: 0,0:12:41.00,0:12:44.00,Default,,0000,0000,0000,,of a little finger of a pinky of a human.
Dialogue: 0,0:12:44.00,0:12:46.00,Default,,0000,0000,0000,,And it was well enough preserved
Dialogue: 0,0:12:46.00,0:12:49.00,Default,,0000,0000,0000,,so we could determine the DNA from this individual,
Dialogue: 0,0:12:49.00,0:12:51.00,Default,,0000,0000,0000,,even to a greater extent
Dialogue: 0,0:12:51.00,0:12:53.00,Default,,0000,0000,0000,,than for the Neanderthals actually,
Dialogue: 0,0:12:53.00,0:12:55.00,Default,,0000,0000,0000,,and start relating it to the Neanderthal genome
Dialogue: 0,0:12:55.00,0:12:58.00,Default,,0000,0000,0000,,and to people today.
Dialogue: 0,0:12:58.00,0:13:00.00,Default,,0000,0000,0000,,And we found that this individual
Dialogue: 0,0:13:00.00,0:13:03.00,Default,,0000,0000,0000,,shared a common origin for his DNA sequences
Dialogue: 0,0:13:03.00,0:13:07.00,Default,,0000,0000,0000,,with Neanderthals around 640,000 years ago.
Dialogue: 0,0:13:07.00,0:13:10.00,Default,,0000,0000,0000,,And further back, 800,000 years ago
Dialogue: 0,0:13:10.00,0:13:12.00,Default,,0000,0000,0000,,is there a common origin
Dialogue: 0,0:13:12.00,0:13:14.00,Default,,0000,0000,0000,,with present day humans.
Dialogue: 0,0:13:14.00,0:13:16.00,Default,,0000,0000,0000,,So this individual comes from a population
Dialogue: 0,0:13:16.00,0:13:19.00,Default,,0000,0000,0000,,that shares an origin with Neanderthals,
Dialogue: 0,0:13:19.00,0:13:22.00,Default,,0000,0000,0000,,but far back and then have a long independent history.
Dialogue: 0,0:13:22.00,0:13:24.00,Default,,0000,0000,0000,,We call this group of humans,
Dialogue: 0,0:13:24.00,0:13:26.00,Default,,0000,0000,0000,,that we then described for the first time
Dialogue: 0,0:13:26.00,0:13:28.00,Default,,0000,0000,0000,,from this tiny, tiny little piece of bone,
Dialogue: 0,0:13:28.00,0:13:30.00,Default,,0000,0000,0000,,the Denisovans,
Dialogue: 0,0:13:30.00,0:13:33.00,Default,,0000,0000,0000,,after this place where they were first described.
Dialogue: 0,0:13:33.00,0:13:36.00,Default,,0000,0000,0000,,So we can then ask for Denisovans
Dialogue: 0,0:13:36.00,0:13:38.00,Default,,0000,0000,0000,,the same things as for the Neanderthals:
Dialogue: 0,0:13:38.00,0:13:42.00,Default,,0000,0000,0000,,Did they mix with ancestors of present day people?
Dialogue: 0,0:13:42.00,0:13:44.00,Default,,0000,0000,0000,,If we ask that question,
Dialogue: 0,0:13:44.00,0:13:46.00,Default,,0000,0000,0000,,and compare the Denisovan genome
Dialogue: 0,0:13:46.00,0:13:48.00,Default,,0000,0000,0000,,to people around the world,
Dialogue: 0,0:13:48.00,0:13:50.00,Default,,0000,0000,0000,,we surprisingly find
Dialogue: 0,0:13:50.00,0:13:52.00,Default,,0000,0000,0000,,no evidence of Denisovan DNA
Dialogue: 0,0:13:52.00,0:13:57.00,Default,,0000,0000,0000,,in any people living even close to Siberia today.
Dialogue: 0,0:13:57.00,0:13:59.00,Default,,0000,0000,0000,,But we do find it in Papua New Guinea
Dialogue: 0,0:13:59.00,0:14:03.00,Default,,0000,0000,0000,,and in other islands in Melanesia and the Pacific.
Dialogue: 0,0:14:03.00,0:14:05.00,Default,,0000,0000,0000,,So this presumably means
Dialogue: 0,0:14:05.00,0:14:08.00,Default,,0000,0000,0000,,that these Denisovans had been more widespread in the past,
Dialogue: 0,0:14:08.00,0:14:11.00,Default,,0000,0000,0000,,since we don't think that the ancestors of Melanesians
Dialogue: 0,0:14:11.00,0:14:13.00,Default,,0000,0000,0000,,were ever in Siberia.
Dialogue: 0,0:14:13.00,0:14:15.00,Default,,0000,0000,0000,,So from studying
Dialogue: 0,0:14:15.00,0:14:18.00,Default,,0000,0000,0000,,these genomes of extinct humans,
Dialogue: 0,0:14:18.00,0:14:21.00,Default,,0000,0000,0000,,we're beginning to arrive at a picture of what the world looked like
Dialogue: 0,0:14:21.00,0:14:24.00,Default,,0000,0000,0000,,when modern humans started coming out of Africa.
Dialogue: 0,0:14:24.00,0:14:27.00,Default,,0000,0000,0000,,In the West, there were Neanderthals;
Dialogue: 0,0:14:27.00,0:14:29.00,Default,,0000,0000,0000,,in the East, there were Denisovans --
Dialogue: 0,0:14:29.00,0:14:31.00,Default,,0000,0000,0000,,maybe other forms of humans too
Dialogue: 0,0:14:31.00,0:14:33.00,Default,,0000,0000,0000,,that we've not yet described.
Dialogue: 0,0:14:33.00,0:14:36.00,Default,,0000,0000,0000,,We don't know quite where the borders between these people were,
Dialogue: 0,0:14:36.00,0:14:38.00,Default,,0000,0000,0000,,but we know that in Southern Siberia,
Dialogue: 0,0:14:38.00,0:14:40.00,Default,,0000,0000,0000,,there were both Neanderthals and Denisovans
Dialogue: 0,0:14:40.00,0:14:43.00,Default,,0000,0000,0000,,at least at some time in the past.
Dialogue: 0,0:14:43.00,0:14:46.00,Default,,0000,0000,0000,,Then modern humans emerged somewhere in Africa,
Dialogue: 0,0:14:46.00,0:14:49.00,Default,,0000,0000,0000,,came out of Africa, presumably in the Middle East.
Dialogue: 0,0:14:49.00,0:14:52.00,Default,,0000,0000,0000,,They meet Neanderthals, mix with them,
Dialogue: 0,0:14:52.00,0:14:55.00,Default,,0000,0000,0000,,continue to spread over the world,
Dialogue: 0,0:14:55.00,0:14:58.00,Default,,0000,0000,0000,,and somewhere in Southeast Asia,
Dialogue: 0,0:14:58.00,0:15:00.00,Default,,0000,0000,0000,,they meet Denisovans and mix with them
Dialogue: 0,0:15:00.00,0:15:03.00,Default,,0000,0000,0000,,and continue on out into the Pacific.
Dialogue: 0,0:15:03.00,0:15:06.00,Default,,0000,0000,0000,,And then these earlier forms of humans disappear,
Dialogue: 0,0:15:06.00,0:15:09.00,Default,,0000,0000,0000,,but they live on a little bit today
Dialogue: 0,0:15:09.00,0:15:11.00,Default,,0000,0000,0000,,in some of us --
Dialogue: 0,0:15:11.00,0:15:14.00,Default,,0000,0000,0000,,in that people outside of Africa have two and a half percent of their DNA
Dialogue: 0,0:15:14.00,0:15:16.00,Default,,0000,0000,0000,,from Neanderthals,
Dialogue: 0,0:15:16.00,0:15:18.00,Default,,0000,0000,0000,,and people in Melanesia
Dialogue: 0,0:15:18.00,0:15:21.00,Default,,0000,0000,0000,,actually have an additional five percent approximately
Dialogue: 0,0:15:21.00,0:15:24.00,Default,,0000,0000,0000,,from the Denisovans.
Dialogue: 0,0:15:24.00,0:15:26.00,Default,,0000,0000,0000,,Does this then mean that there is after all
Dialogue: 0,0:15:26.00,0:15:28.00,Default,,0000,0000,0000,,some absolute difference
Dialogue: 0,0:15:28.00,0:15:31.00,Default,,0000,0000,0000,,between people outside Africa and inside Africa
Dialogue: 0,0:15:31.00,0:15:33.00,Default,,0000,0000,0000,,in that people outside Africa
Dialogue: 0,0:15:33.00,0:15:35.00,Default,,0000,0000,0000,,have this old component in their genome
Dialogue: 0,0:15:35.00,0:15:37.00,Default,,0000,0000,0000,,from these extinct forms of humans,
Dialogue: 0,0:15:37.00,0:15:39.00,Default,,0000,0000,0000,,whereas Africans do not?
Dialogue: 0,0:15:39.00,0:15:42.00,Default,,0000,0000,0000,,Well I don't think that is the case.
Dialogue: 0,0:15:42.00,0:15:44.00,Default,,0000,0000,0000,,Presumably, modern humans
Dialogue: 0,0:15:44.00,0:15:46.00,Default,,0000,0000,0000,,emerged somewhere in Africa.
Dialogue: 0,0:15:46.00,0:15:49.00,Default,,0000,0000,0000,,They spread across Africa also, of course,
Dialogue: 0,0:15:49.00,0:15:52.00,Default,,0000,0000,0000,,and there were older, earlier forms of humans there.
Dialogue: 0,0:15:52.00,0:15:54.00,Default,,0000,0000,0000,,And since we mixed elsewhere,
Dialogue: 0,0:15:54.00,0:15:56.00,Default,,0000,0000,0000,,I'm pretty sure that one day,
Dialogue: 0,0:15:56.00,0:15:58.00,Default,,0000,0000,0000,,when we will perhaps have a genome
Dialogue: 0,0:15:58.00,0:16:00.00,Default,,0000,0000,0000,,of also these earlier forms in Africa,
Dialogue: 0,0:16:00.00,0:16:02.00,Default,,0000,0000,0000,,we will find that they have also mixed
Dialogue: 0,0:16:02.00,0:16:05.00,Default,,0000,0000,0000,,with early modern humans in Africa.
Dialogue: 0,0:16:06.00,0:16:08.00,Default,,0000,0000,0000,,So to sum up,
Dialogue: 0,0:16:08.00,0:16:10.00,Default,,0000,0000,0000,,what have we learned from studying genomes
Dialogue: 0,0:16:10.00,0:16:12.00,Default,,0000,0000,0000,,of present day humans
Dialogue: 0,0:16:12.00,0:16:14.00,Default,,0000,0000,0000,,and extinct humans?
Dialogue: 0,0:16:14.00,0:16:16.00,Default,,0000,0000,0000,,We learn perhaps many things,
Dialogue: 0,0:16:16.00,0:16:21.00,Default,,0000,0000,0000,,but one thing that I find sort of important to mention
Dialogue: 0,0:16:21.00,0:16:24.00,Default,,0000,0000,0000,,is that I think the lesson is that we have always mixed.
Dialogue: 0,0:16:24.00,0:16:26.00,Default,,0000,0000,0000,,We mixed with these earlier forms of humans,
Dialogue: 0,0:16:26.00,0:16:28.00,Default,,0000,0000,0000,,wherever we met them,
Dialogue: 0,0:16:28.00,0:16:32.00,Default,,0000,0000,0000,,and we mixed with each other ever since.
Dialogue: 0,0:16:32.00,0:16:34.00,Default,,0000,0000,0000,,Thank you for your attention.
Dialogue: 0,0:16:34.00,0:16:40.00,Default,,0000,0000,0000,,(Applause)