Transcript: Humans have existed only for a couple of million years, a tiny fraction of the span of life on Earth. For most of this time, we left a small footprint on the Earth. Humans were just hunter-gatherers, and there were only a few million or tens of millions of them until relatively recently. Now there are over six billion humans, and in the last few hundred years and at an accelerating rate in the last fifty years, we’ve been altering the global chemistry and climate of our planet. There is demonstrable impact of industrial activity on the carbon dioxide level in the atmosphere and, arguably, global warming itself. Also, our use of the planet as a consumable resource has lead to a stunning loss in biodiversity in the last few decades. Looking backward in time, this period will be viewed as a great dying on par with any of the mass extinctions in the history of the Earth. Apollo 8 gave us a view of our planet as a delicate orb suspended in space. Only time will tell whether we can tread lightly enough on our planet to leave it for our distant ancestors.