What's your digital footprint?
It's called a footprint because it's the mark you leave on the world. We can trace humans back a long way, but we don't have much of a physical footprint for most of them. In fact, if we hadn't done the math on evolution, we really couldn't prove the existence of almost all of the human race! The first few centuries of humans is represented by just a few bones, the first major civilisations are now little more than monuments but today, well - now we know everything about everyone.
How big is your footprint?