Humans are now living in a new geological epoch of our own making: the Anthropocene. Or so we’re told. Whereas some epochs in Earth history stretch more than 40 million years, this new chapter started maybe 400 years ago, when carbon dioxide dipped by a few parts per million in the atmosphere. Or perhaps, as a panel of scientists voted earlier this year, the epoch started as recently as 75 years ago, when atomic weapons began to dust the planet with an evanescence of strange radioisotopes.
These are unusual claims about geology, a field that typically deals with mile-thick packages of rock stacked up over tens of millions of years, wherein entire mountain ranges are born and weather away to nothing within a single unit of time, in which extremely precise rock dates—single-frame snapshots from deep time—can come with 50,000-year error bars, a span almost 10 times as long as all of recorded human history. If having an epoch shorter than an error bar seems strange, well, so is the Anthropocene.