Think for a moment about every single person you've ever met in your life.

Then think about everybody you've ever heard of and finally think about everybody alive on the planet right now.

No matter how far away or close all of these people may seem, including me talking to you right now through this video, all of us are related to you and all of you are related to me.

So how can this be using some very simple math?

We can take a glance at your family tree.

You obviously had to parents and your parents each had two parents of their own, which means you have four grand parents.

You have eight great grand parents and this number doubles each generation.

You go back just five generations ago or 125 years before the date you were born, you theoretically would have had 32 ancestors living on Earth at that time.

However, going back 1000 years before you were born or 40 generations ago, you would find with this math that you would have over a trillion ancestors living in the Middle Ages, which is more people than have ever existed in all of time combined.

Obviously, there's a variable we haven't accounted for in these calculations yet, and that variable is incest.

Ah, lot of it for most of human history, the only people somebody may ever really meet where the people in their local village, town or tribe.

This obviously limited the dating pool to just a handful of options.

And those options often included people like cousins.

Not all of your ancestors air unique toe only you or your family.

If you compare your family tree with your friends tree and you go back far enough, you'll see the shape of the tree slowly vanish and see something that resembles more of a Web.

As you draw your two webs out, you'll eventually find a common ancestor between yourselves at some point, which would make you both distantly related the further back in time we go, the more common ancestors all of us end up having about 0.5% of the modern human population conclusion direct ancestry from Genghis Khan, largely in the region of Asia, between China and Uzbekistan.

Going even further, nearly anybody with European ancestry can trace their origins to the same group of ancestors roughly 1000 years ago.

This means that statistically, if you have European ancestry, anybody living in Europe around the ninth century who had Children and grandchildren is one of your direct ancestors, meaning that since Charlemagne had 18 kids, he's most likely somewhere in your family Web.

But who is the most recent person that all of us alive on earth watching this video could mutually trace all of our ancestries back to.

This person is known as the most recent common ancestor, or M R C a.

And he or she is believed to have existed not terribly long ago.

They may have existed as recently as just 300 b.

C.

E, just after the conquest of Alexander the Great, and they almost certainly lived somewhere in East Asia.

In either Kamchatka, Japan, Taiwan or Indonesia.

This person had amazing reproductive success and was likely a merchant that traveled extensively with their offspring, venturing, often creating their own offspring over time in the far flung parts of the world like the America's and Australia.

This single human who lived there in this time is the direct ancestor of every single person alive today, which links all of us together in the giant family web that we call humanity.

But it doesn't mean that MRC A was the first person to have Children.

Nor does it mean that nobody else alive then has direct descendants.

Today there are many MRC A is simply the first person in world history who can count universal descendants today.

But many of our ancestors lived significantly further in the past than they.

A 9000 year old skeleton dubbed Cheddar Man was discovered in a cave near the English city of Cheddar back in 19 oh, three.

Recent DNA analysis of the remains revealed something astonishing.

9000 years and 300 generations later, Cheddar Man has a direct descendants living today, and he Onley lives half a mile away from the side of the cave and teaches history.

If you rewind the clock even further back, it's possible that 70,000 years ago the entire global population of humans may have shrunk to a little as 10 1000 people.

That's only 1/9 of the seating capacity at Wembley Stadium.

And then, when you consider those few people were spread out across Africa and Eurasia, you remember what I said earlier.

Most people only ever dated people who lived nearby because they literally had no other options.

We all share multiple common ancestors that all of us can claim to be descended from.

It's just that that person in 300 B.

C is the most recent one that all of us can claim if you think about it in terms like this, if you fail to have Children, you're the first person in an unbroken chain going back hundreds of thousands of years to fail to do so.

In fact, it's even more serious than that when you consider the most recent common ancestor of all living things.

Today, this organism is known as the last universal common ancestor, or Luca.

For short.

Luca is believed to have existed 3.5 to 3.8 billion years ago and everything that's a life on earth right now, from you and me to bananas, that annoying mosquito Greg and the bacteria on your face are all direct descendants of it.

When you think like that, if you fail to reproduce during your life, you're the first organism in an unbroken chain going back over three billion years to fail.

And that may make your ancient ancestor Luca rather sad.

But what's interesting about all of this is that if you go back far enough, not only is all of humanity one giant, interconnected family, but all of life itself on Earth is just one incomprehensibly huge, interconnected family.

So the next time you stop that bug or swat that mosquito, remember that you both are technically part of the same big family.

The origins of humanity and life itself are as mysterious as they are interesting, but they're still a surprising amount that we actually know.

Using math, we can calculate certain things like where your ancestors probably originated from, and we can come up with theories like who all of us are directly descended from.

The scientists that work.

To figure all of these things out are like detectives investigating 1000 year old crime scenes that literally impact all of us today, and the computational biology course at Brilliant will explain to you how all of it works and why it affects you personally.

The course has an entire section dedicated to human ancestry.

That this video was heavily influenced by brilliant, as I'm sure you know by now is the best place to learn about complex topics because they teach you the intuitive ideas behind them.

So you understand how it all works together rather than just memorizing phrases.

If you want to become the kind of person who can explain where your ancestors came from, going back thousands of years based on your own genetic evidence, then brilliant is the right place for you as they have courses not only on that, but on plenty of other interesting topics like computer science, artificial neural networks or logic.