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  • This is you.

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

  • on your head.

  • How many ancestors do you have?

  • Well, you have two parents.

  • Four grandparents.

  • And eight great-grandparents.

  • Four generations back, your direct ancestors total 30.

  • If we continue down this line, doubling every step, just 40 generations ago we’d find

  • a trillion ancestors, all living *at the same time*.

  • Which isridiculous.

  • That's not only more people than have ever been alive, it's more stars than are in

  • the Milky Way.

  • Since our species came on the scene 200,000 years ago, there have been maybe 7 or 8 *thousand*

  • generations of humans leading up toyou.

  • So where are all your missing ancestors?

  • Clearly, there’s been some inbreeding.

  • [OPEN]

  • Were not talking banjo-playing, King-of-Spain, Cersei-Jaime inbreeding, but every family

  • tree inevitably grows forks.

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

  • Even people like Charles Darwin and Albert Einstein married their first cousins.

  • Because so many people with shared ancestors have reproduced, our number of actual ancestors

  • is much smaller than what simple math tells us.

  • If we replace that with fancy math, factoring in how people moved and lived and paired up

  • life expectancy, trade, geography, Genghis Khanwe find something interesting: every

  • human alive today shares a common ancestor in their family tree, and this person lived

  • only around 3,000 years ago.

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

  • that you share the same great great great great great (fast foward) great grandfather

  • or grandmother.

  • But we don’t know who that person was.

  • The math tells us they must have existed, but they didn’t leave fossils or artifacts.

  • Or like, a note or something.

  • Though, writing birthday cards for each of their 7.4 Billion great great great great

  • great (fast forward) great grandchildren would have been nice gesture.

  • But we all carry a record of our ancestors in our genes.

  • Because DNA is copied over and over, every so often a mistake is written in.

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

  • Like that, but since most of our DNA can be changed without affecting how things work,

  • many of these mutations slip through to the next generation.

  • These genetic changes accumulate at a steady rate through time, so scientists can read

  • them like a molecular clock, and estimate how much time has passed.

  • And which changes individuals share tell us how closely or distantly related they are.

  • Humans *seem* really different, but on a DNA level were remarkably similar.

  • Groups of chimps in Central Africa, living right next to each other, show more genetic

  • variation than we find in the entire human population.

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

  • and that at one point our population was small, maybe as few as 10,000 of us.

  • To put that in perspective, that’s only a third of your average Bruce Springsteen

  • crowd.

  • Sorry Boss.

  • Today, any two humans only differ by about 1 out of 1000 DNA base pairs.

  • But our genome is so big, that’s still millions of single letter differences, or SNPs, for

  • single nucleotide polymorphism”.

  • We tend to see combinations of these changes, chunks of SNPs, associated with different

  • geographic locations.

  • Companies that test your DNA ancestry read thousands of these single letter changes in

  • your genome, to make a sort of signature of your unique genetic variation.

  • Then they compare your signature to thousands of reference individuals from various parts

  • of the world, and do a bunch of fancy math to see which parts of your genome most likely

  • came from certain geographic areas.

  • My genetic results: Pretty much look like this.

  • My ancNewsprestors, on both sides of my family, are from Northern Europe and Scandinavia,

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

  • Neanderthal DNA than 2/3rds of people.

  • Confused why I have Neanderthal DNA?

  • You should watch our last video. I didn’t find any surprises, but many people learn

  • about ancestry they didn’t know they had.

  • Where we come from isn’t always obvious on the outside, but DNA doesn’t lie.

  • Before, using math, we identified an ancestor, not too long ago, that’s related to all

  • of us.

  • But that person’s genetic influence has been shuffled so much it’s invisible in

  • our DNA today.

  • Is there someone whose genes have been passed on, unbroken, to today?

  • Some leftover fingerprint from the mother of everyone alive?

  • There is.

  • You have a 47th chromosome.

  • It lives in mitochondria, the POWERHOUSE OF THE CELL! – so were doing that again?

  • Okmitochondria used to be free-swimming.

  • They have their own genetic material.

  • Unlike your other 46 chromosomes, there’s no shuffling when it’s passed between generations.

  • What’s more, all your mitochondria came from your mother’s egg, not your father’s

  • sperm.

  • They trace an unbroken line of ancestors stretching back through every female in your family tree.

  • By comparing the changes that have accumulated over the millennia, we find the most ancient

  • human mitochondrial DNA comes from Africa, where our species originated.

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

  • Other Homo sapiens females lived alongside her, but only her lineage lives on today,

  • all other Homo sapiens lineages are extinct.

  • This is mitochondrial Eve.

  • And every single one of us, descend from her.

  • In the truest sense, we really are family.

  • Even if were just hundredth cousins or something.

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

  • into the future.

  • Today we have more power to mold that future, down to the genetic level, than weve ever

  • had before.

  • So what might our speciesfuture look like?

  • Next time.

  • Stay curious.

  • This video is part of a special series were doing about the story of our species: Where

  • we came from, how were all connected, and where were going.

  • If you haven’t already, check out part 1 and 2 to trace the fossils in our family tree

  • and learn why were the only humans left.

  • And be sure to subscribe so you don’t miss any of our videos.

This is you.

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