" Something in the order of a 107 billion modern humans have existed, though this number depends on when exactly you start counting. All of them – of us – are close cousins, as our species has a single African origin. We don’t quite have the language to describe what that really means. It doesn’t, for example, mean a single couple, a hypothetical Adam and Eve. We think of families and pedigrees and genealogies and ancestry, and we try to think of the deep past in the same way. Who were my ancestors? You might have a simple, traditional family structure or, like me, it could be handsomely untidy, and its tendrils jumbled like old wires in a drawer. But no matter which, everyone’s past becomes muddled sooner or later. "

― Adam Rutherford , A Brief History of Everyone Who Ever Lived: The Stories in Our Genes