The Earth is a big thing; if you divided it up evenly among its 7 billion inhabitants, they would get almost one trillion tonnes each.
To think that the workings of so vast an entity could be lastingly changed by a species that has been scampering across its surface for less than 1 percent of 1 percent of its history seems, on the face of it, absurd. But it is not. Humans have become a force of nature reshaping the planet on a geological scale—but at a far-faster-than-geological speed.
Human interaction with the land has altered the ecosystem so deeply that it has spawned a new geological era—the Anthropocene—ending the Holocene, an epoch of stable climate that has held sway over the last 12,000 years.
It’s now widely agreed that it began around 1950, shaped by the mushroom clouds of radioactive material upchucked by the series of nuclear tests. Previously, it was pegged at around 1800, believed to have been triggered by the fumes of the Industrial Revolution.