This reminds me of a passage from Richard Dawkins' "Unweaving the Rainbow."
"We are going to die, and that makes us the lucky ones. Most people are never going to die because they are never going to be born. The potential people who could have been here in my place but who will in fact never see the light of day outnumber the sand grains of Arabia. Certainly those unborn ghosts include greater poets than Keats, scientists greater than Newton. We know this because the set of possible people allowed by our DNA so massively exceeds the set of actual people. In the teeth of these stupefying odds it is you and I, in our ordinariness, that are here."
I too thought of that passage but also this from Watchmen:
"There are thermodynamic miracles, events with odds against so astronomical they're effectively impossible, like oxygen spontaneously becoming gold; I long to observe such a thing. And yet, in each human coupling, a thousand million sperm vie for a single egg. Multiply those odds by countless generations, against the odds of your ancestors being alive; meeting; siring this precise son; that exact daughter, until your mother loves a man she has every reason to hate, and of that union, of the thousand million children competing for fertilization, it was you, only you, that emerged. To distill so specific a form from that chaos of improbability, like turning air to gold, that is the crowning unlikelihood, the thermodynamic miracle. The world is so full of people, so crowded with these miracles that they become commonplace and we forget. I forget. We gaze continually at the world and it grows dull in our perceptions. Yet seen from another's vantage point, as if new, it may still take our breath away. Come, dry your eyes, for you are life, rarer than a quark and unpredictable beyond the dreams of Heisenberg, the clay in which the forces that shape all things leave their fingerprints most clearly."
"We are going to die, and that makes us the lucky ones. Most people are never going to die because they are never going to be born. The potential people who could have been here in my place but who will in fact never see the light of day outnumber the sand grains of Arabia. Certainly those unborn ghosts include greater poets than Keats, scientists greater than Newton. We know this because the set of possible people allowed by our DNA so massively exceeds the set of actual people. In the teeth of these stupefying odds it is you and I, in our ordinariness, that are here."