0:00:02.889,0:00:04.156
This is you.

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And these are your ancestors, a huge pyramid[br]stretching into the past and balancing right

0:00:10.214,0:00:11.865
on your head.

0:00:12.038,0:00:14.223
How many ancestors do you have?

0:00:14.309,0:00:15.975
Well, you have two parents.

0:00:16.015,0:00:17.016
Four grandparents.

0:00:17.016,0:00:18.933
And eight great-grandparents.

0:00:19.007,0:00:22.366
Four generations back, [br]your direct ancestors total 30.

0:00:22.429,0:00:27.074
If we continue down this line, doubling every[br]step, just 40 generations ago we’d find

0:00:27.074,0:00:31.019
a trillion ancestors, all living <i>at the same[br]time</i>.

0:00:31.055,0:00:32.101
Which is… ridiculous.

0:00:33.002,0:00:37.086
That’s not only more people than have ever[br]been alive, it’s more stars than are in

0:00:37.086,0:00:38.109
the Milky Way.

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Since our species came on the scene 200,000[br]years ago, there’ve been maybe 7 or 8 <i>thousand</i>

0:00:44.019,0:00:47.020
generations of humans leading up to… you.

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So where are all your missing ancestors?

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Clearly, there’s been some inbreeding.

0:00:53.789,0:00:54.789
[OPEN]

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We’re not talking banjo-playing, King-of-Spain,[br]Cersei-Jamie inbreeding, but every family

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tree inevitably grows forks.

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Before Tinder, choices for mates were[br]often limited to as far as you could walk.

0:01:07.068,0:01:10.116
Even people like Charles Darwin and Albert[br]Einstein married their first cousins.

0:01:14.024,0:01:18.116
Because so many people with shared ancestors[br]have reproduced, our number of actual ancestors

0:01:19.016,0:01:21.093
is much smaller than what simple math tells[br]us.

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If we replace that with fancy math, factoring[br]in how people moved and lived and paired up…

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life expectancy, trade, geography, Genghis[br]Khan… we find something interesting: every

0:01:34.002,0:01:38.007
human alive today shares a common ancestor[br]in their family tree, and this person lived

0:01:38.052,0:01:40.052
only around 3,000 years ago.

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That’s right, next time you get in a fight[br]with a stranger on the internet, just remember

0:01:44.031,0:01:51.046
that you share the same great great great[br]great great (fast foward) great grandfather

0:01:51.046,0:01:52.205
or grandmother.

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But we don’t know who that person was.

0:01:55.059,0:01:58.138
The math tells us they must have existed,[br]but they didn’t leave fossils or artifacts.

0:01:59.038,0:02:01.557
Or like, a note or something.

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Though, writing birthday cards for each of[br]their 7.4 Billion great great great great

0:02:08.036,0:02:10.634
great (fast forward) great grandchildren would[br]have been nice gesture.

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But we all carry a record of our ancestors[br]in our genes.

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Because DNA is copied over and over, every[br]so often a mistake is written in.

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You know how when you make a copy of a copy,[br]it’s doesn't come out as sharp?

0:02:22.064,0:02:26.091
Like that, but since most of our DNA can be[br]changed without affecting how things work,

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many of these mutations slip through to the[br]next generation.

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These genetic changes accumulate at a steady[br]rate through time, so scientists can read

0:02:35.023,0:02:39.068
them like a molecular clock, and estimate[br]how much time has passed.

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And which changes individuals share tell us[br]how closely or distantly related they are.

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Humans <i>seem</i> really different, but on a DNA[br]level we’re remarkably similar.

0:02:49.709,0:02:53.754
Groups of chimps in Central Africa, living[br]right next to each other, show more genetic

0:02:54.159,0:02:58.330
variation than we find in the entire human[br]population.

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This genetic similarity tells us that our[br]species is new, in the big scheme of things,

0:03:02.082,0:03:06.180
and that at one point our population was small,[br]maybe as few as 10,000 of us.

0:03:07.008,0:03:11.012
To put that in perspective, that’s only[br]a third of your average Bruce Springsteen

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crowd.

0:03:12.084,0:03:13.084
Sorry Boss.

0:03:13.084,0:03:18.145
Today, any two humans only differ by about[br]1 out of 1000 DNA base pairs.

0:03:19.045,0:03:23.130
But our genome is so big, that’s still millions[br]of single letter differences, or SNPs, for

0:03:24.003,0:03:26.049
“single nucleotide polymorphism”.

0:03:26.076,0:03:30.103
We tend to see combinations of these changes,[br]chunks of SNPs, associated with different

0:03:31.003,0:03:33.042
geographic locations.

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Companies that test your DNA ancestry read[br]thousands of these single letter changes in

0:03:37.021,0:03:41.034
your genome, to make a sort of signature of[br]your unique genetic variation.

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Then they compare your signature to thousands[br]of reference individuals from various parts

0:03:46.018,0:03:50.039
of the world, and do a bunch of fancy math[br]to see which parts of your genome most likely

0:03:50.039,0:03:52.068
came from certain geographic areas.

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My genetic results: Pretty much look like[br]this.

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My ancNewsprestors, on both sides of my family,[br]are from Northern Europe and Scandinavia,

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which explains my last name, why I’m tall,[br]why I don’t tan, and also why I carry more

0:04:06.189,0:04:09.290
Neanderthal DNA than 2/3rds of people.

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Confused why I have Neanderthal DNA?

0:04:10.098,0:04:14.197
You should watch our last video. I didn’t[br]find any surprises, but many people learn

0:04:15.097,0:04:17.168
about ancestry they didn’t know they had.

0:04:18.069,0:04:23.080
Where we come from isn’t always obvious[br]on the outside, but DNA doesn’t lie.

0:04:23.008,0:04:27.649
Before, using math, we identified an ancestor,[br]not too long ago, that’s related to all

0:04:28.441,0:04:29.441
of us.

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But that person’s genetic influence has[br]been shuffled so much it’s invisible in

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our DNA today.

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Is there someone whose genes have been passed[br]on, unbroken, to today?

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Some leftover fingerprint from the mother[br]of everyone alive?

0:04:43.093,0:04:44.099
There is.

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You have a 47th chromosome.

0:04:47.076,0:04:54.173
It lives in mitochondria, the POWERHOUSE OF[br]THE CELL! – so we’re doing that again?

0:04:55.073,0:04:57.073
Ok–mitochondria used to be free-swimming.

0:04:57.073,0:04:58.166
They have their own genetic material.

0:04:59.066,0:05:03.134
Unlike your other 46 chromosomes, there’s[br]no shuffling when it’s passed between generations.

0:05:04.034,0:05:08.043
What’s more, all your mitochondria came[br]from your mother’s egg, not your father’s

0:05:08.043,0:05:09.043
sperm.

0:05:09.043,0:05:14.102
They trace an unbroken line of ancestors stretching[br]back through every female in your family tree.

0:05:15.002,0:05:19.034
By comparing the changes that have accumulated[br]over the millennia, we find the most ancient

0:05:19.034,0:05:24.035
human mitochondrial DNA comes from Africa,[br]where our species originated.

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We can even trace it back to one woman, about[br]150,000 years ago.

0:05:29.026,0:05:34.058
Other Homo sapiens females lived alongside[br]her, but only her lineage lives on today,

0:05:34.058,0:05:36.139
all other Homo sapiens lineages are extinct.

0:05:37.039,0:05:39.040
This is mitochondrial Eve.

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And every single one of us, descend from her.

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In the truest sense, we really are family.

0:05:46.004,0:05:47.072
Even if we’re just hundredth cousins or[br]something.

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But our ancestry isn’t just branches stretching[br]into the past, it’s also a tree that extends

0:05:53.041,0:05:54.077
into the future.

0:05:54.077,0:05:57.174
Today we have more power to mold that future,[br]down to the genetic level, than we’ve ever

0:05:58.074,0:05:59.079
had before.

0:05:59.079,0:06:02.164
So what might our species’ future look like?

0:06:03.064,0:06:04.105
Next time.

0:06:05.005,0:06:06.084
Stay curious.

0:06:06.084,0:06:10.085
This video is part of a special series we’re[br]doing about the story of our species: Where

0:06:10.841,0:06:14.240
we came from, how we’re all connected, and[br]where we’re going.

0:06:14.024,0:06:18.087
If you haven’t already, check out part 1[br]and 2 to trace the fossils in our family tree

0:06:18.087,0:06:20.096
and learn why we’re the only humans left.

0:06:21.077,0:06:24.078
And be sure to subscribe so you don’t miss[br]any of our videos.