Anthropocene Markers Since 1950: Humanity's Signature Is Now Written in Rock

A future geologist, digging through the layers we are laying down today, would not need our books to know we were here. That is the quiet force of a major review published this year in Nature Reviews Earth & Environment: across 12 sites on five continents, researchers found that human activity since the mid-20th century has left a distinct, measurable mark in the planet's geological record. Lake sediments, deep-sea deposits, ice cores, peatlands, coral reefs and cave formations all tell the same story, in different materials and on different continents. The signal is not a metaphor. It is chemistry, sitting in layers that can be dated year by year.

The markers themselves are unglamorous, which is part of why they are convincing. Radioactive fallout from nuclear weapons testing, concentrated from the early 1950s, left a global plutonium signature in sediments around the world. The soot and chemical by-products of fossil fuel combustion rose with the post-war industrial boom. The carbon and nitrogen cycles shifted measurably as fertiliser use, industry and land use scaled up. No single marker carries the argument: the review's authors, 29 scientists in all, assembled more than a hundred lines of evidence, and the pattern is one of abruptness — humans have influenced environments for thousands of years, but the signals become much stronger and more widespread after the 1950s.

One of the most telling sites is also one of the most remote from human bustle. In the Grotta di Ernesto cave in the Italian Alps, stalagmites grow drip by drip, trapping the chemistry of the water that formed them. Andrea Borsato of the University of Newcastle, the review's sole Australia-based author, worked on that cave record. Some globally recognised markers were too weak to show up there, and the review is honest about that unevenness — not every archive records every signal. But enough did, and that is the point: even stone growing in a dark cave, far from any factory or test site, carries traces of industrialisation and nuclear testing. The University of Newcastle team is now extending the cave work into the Pacific, to sites in the Cook Islands, Tonga and French Polynesia, to see how faithfully those environments preserve the same signals.

And yet, formally, we do not live in the Anthropocene. The term, popularised in 2000 by Nobel laureate Paul Crutzen, names the idea that humanity has pushed Earth out of the Holocene, the stable epoch of the last 11,700 years in which civilisation developed. The Anthropocene Working Group, set up in 2009, spent over a decade building the case and proposed a start date in the early 1950s, with Crawford Lake in Ontario, Canada, as the "golden spike" reference site. In March 2024, the Subcommission on Quaternary Stratigraphy voted the proposal down, 12 to 4. The working group was later disbanded, and its members regrouped as an informal group of more than 50 scientists who continue the work.

The objections are serious, and worth stating plainly rather than waving away. An epoch that spans barely 70 years sits awkwardly beside units that typically last thousands or millions of years. The start date is genuinely contested: farming, the Industrial Revolution and the 1950s all have defenders, and a boundary drawn at 1952 can look like it erases the centuries of human transformation that came before. Some geologists argue the Anthropocene is better treated as a geological event — a profound transformation of Earth systems — rather than a formal unit of time. Others in the informal group are exploring a smaller step: designating Crawford Lake as the marker for an age within the Holocene, rather than a whole new epoch.

I read the new review as strengthening the evidence while leaving the institutional question exactly where it was. The 2024 vote was not a judgement that humans have had little effect; nobody in the debate doubts that. It was a judgement about what kind of thing a geological epoch is, and whether a 70-year unit belongs in that system. Publishing the full evidence in peer-reviewed form, after it was previously scrutinised behind closed doors, lets the wider community weigh it in the open.

My prediction is that the formal question will stay unresolved for a while yet. By the end of 2027, I expect the Anthropocene will still not be a formally ratified epoch on the International Chronostratigraphic Chart. The stratigraphic process moves slowly, the 2024 vote was decisive, and no revised proposal has been put forward. The rocks, meanwhile, will keep recording us whether or not we agree what to call the layer. That is the stranger part of this story: we are already writing in a medium that outlasts our arguments about it, and future readers of that record will not need our permission to read it.