For me it is the fact that our blood contains iron. I earlier used to believe the word stood for some ‘organic element’ since I couldn’t accept we had metal flowing through our supposed carbon-based bodies, till I realized that is where the taste and smell of blood comes from.
Well I don't need to meet everybody. There's no need to meet anyone who doesn't match my sexual preferences, so that's half right there. Then we can also cut everyone who's sexual preferences I don't meet, as well as anyone outside of a given age range (most of the people on earth are much younger than me and would be inappropriate for me to date). We can probably get that down to about 50-60 years. (At one second per person).
The thought experiment was just an attempt to show how hard it is to wrap our minds around big numbers. Even a tangible number such as the amount of people in the world.