There's no doubt if you could go 5, 10, 15 million years into the future and dig down to 2016, you would be able to find the geological evidence that humans occupied the planet.

When the dinosaurs go extinct and 75 percent of life goes extinct after a meteor hits the planet, that's an era boundary. That's when we change from the Mesozoic to the Cenozoic.

If you were back in the Cretaceous Period - the last of the time of the dinosaurs - and you were driving from New York to Philadelphia on the New Jersey Turnpike, you would be driving across water.

We're changing things, in many cases in irreparable ways, and that will certainly be recorded in the geological record.

There's no doubt if you could go 5, 10, 15 million years into the future and dig down to 2016, you would be able to find the geological evidence that humans occupied the planet.

The technical definition of the Holocene has to do with the extinction of a snail species in Sicily.

If we want to know how the Earth's biosphere is going to respond to the things that humans are doing to the planet right now, the only evidence that we have is how biotic systems have responded in the past.