If the Earth formed about 4.54 billion years ago at the shoulder, animals of any kind appear within the palm, and more familiar (to us) lifeforms originate at the first knuckle. Movement along the fingers represent the periods that followed, incorporating, for example, the Jurassic. And humans? The 11,700-year-old Holocene marks the start of a global spread of homo sapiens – “a microscopic sliver at the tip of a fingernail”. The beginning of the proposed Anthropocene, whether we go with a starting point of a mooted 400 years, 70 or somewhere in between, is a tiny speck within this sliver.

So, have homo sapiens created a new geological era? In simple terms, there is something of a case here – there’s plenty of evidence for human impact in the geological record, from signatures of human-induced climate change, atomic testing, and much more. But a fuller appreciation of deep time should actually make us wary of the Anthropocene label, maybe even shift our image of ourselves and what it means to inhabit the Earth at this time. Here’s why.

Mass extinction

Around 66m years ago, a mass extinction event took place, wiping out around three quarters of all species. This was most likely the result of an enormous asteroid impact – a conclusion reached after the discovery of a thin but distinct layer of sediment in the geologic record from this time, containing elements abundant in asteroids.

Mass extinction offered an opportunity for the rise of mammals as dominant lifeforms – ushering in the Cenezoic (“new life”) era. This thin layer of comet dust in the rock record represents a brief but vital transition between much thicker preceding and subsequent layers. But no one refers to what followed the mass extinction event as the “Cometocene”. That just wouldn’t make sense – the impact was a one-off event, significant in the context of deep time only in that it ushered in new foundations for life that then stretched out for millions of years into the far future.