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.
It's kind of an old concept. The idea is that truly new discoveries, like new theories and inventions rather than expansions or extensions, mostly happen by serendipity. So if you have more people churning ideas you get a higher probability of winning serendipity.