Are We All Related?


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 is… ridiculous. 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’ve been maybe 7 or 8 *thousand* generations of humans leading up to… you. So where are all your missing ancestors? Clearly, there’s been some inbreeding. [OPEN] We’re not talking banjo-playing, King-of-Spain,
Cersei-Jamie 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
Khan… we 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 we’re 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 we’re doing that again? Ok–mitochondria 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 we’re 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 we’ve ever had before. So what might our species’ future look like? Next time. Stay curious. This video is part of a special series we’re
doing about the story of our species: Where we came from, how we’re all connected, and
where we’re going. If you haven’t already, check out part 1
and 2 to trace the fossils in our family tree and learn why we’re the only humans left. And be sure to subscribe so you don’t miss
any of our videos.

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