Passing it on, and on

The oxygen in the atmosphere comes from plants. It is carried by winds across the Earth. Every breath we take includes about a billion oxygen molecules that have been, at one time or another, in the lungs of every one of the fifty billion humans who have ever lived. The simple act of breathing links us in this curiously intimate way with every historical figure and the most obscure of our forebears in every epoch.
- Charles Birch, Regaining Compassion for Humanity and Nature (Kensington NSW: NSW Uni Press, 1993) p.120.