One Ancestor, Eight Billion Descendants

Every stranger you pass is your distant cousin — and the reason is stranger than the word 'cousin' can hold. At some point in your past, not so far back that it feels mythological, there was a person whose descendants are every human being alive today. Not a symbol. Not a metaphor. A specific person who woke up, ate something, had children. Their face is gone. Their name is gone. But something of them is sitting in your cells right now, and in the cells of everyone on every continent, in every city, in every language, without exception. The number you'd expect — the number that feels right — is billions of years. The actual number is somewhere around three thousand generations. That's it. Go back three thousand handshakes between parent and child, and you reach someone who is the ancestor of everyone. This should not be possible. The world is large. Oceans exist. Mountains. Deserts that kill. And yet the math of inheritance is ruthless: it multiplies. One person's descendants double, and double again, and again, until they are everywhere or they are gone. Most bloodlines die. The ones that survive flood the world. What this means is that every family that exists today survived something — or several somethings — that nearly ended them. There was a moment, perhaps more than one, when almost nobody made it through. And almost nobody nearly means you.