The history of life on Earth has been discovered largely by studying fossils, imprints in stone left by the dead remains of ancient animals and plants. Geological eras (such as the Jurassic “age of dinosaurs”) are identified by the mix of fossilized remains found in rocks dating from each era.

If the same geological forces that formed ancient fossils continue to operate into the distant future — and there is every reason to suppose that they will — our own era may also leave distinct traces in the fossil record. Traces that scientists of a far future civilization, whether aliens or descended from humans, may rely on to reconstruct our long-vanished world.

Traces of the Anthropocene

In fact, reports Gizmodo, some geologists and paleontologists argue that the human impact on the world has grown so dramatically in the last century or so as to already mark the beginning of a new geological era, dubbed the Anthropocene.

Whether we are now in the Anthropocene era, and when we entered it, is actively debated among scientists, according to Science Daily. Proponents of the idea suggest that human-caused changes in the numbers and distribution of animals (and plants) are so great that the fossil record will one day record an abrupt transition, not unlike the one seen after an asteroid hit the earth some 65 million years ago and wiped out the dinosaurs.

To illustrate this point, says Science Daily, a recent paper notes that in the present-day state of Michigan, some 96% of the total biomass of living animals belongs to humans and our domestic animals.

If the same proportion holds for the remains that turn into fossils and are eventually dug up by a future civilization, their natural history museums will be filled mainly with fossilized humans, chickens, cattle, dogs and cats. Only an occasional squirrel or deer fossil will preserve a trace of the region’s ancient wildlife.

Says the paper’s lead author, thanks to cemeteries, “in the far future, the fossil record of today will have a huge number of complete hominid skeletons, all lined up in rows.” The paper dubbed this effect the “Anthropocene corpse signal.”

A Transformed World, With New Kinds of Fossils

There could be complicating factors. Fossilized remains, as Science magazine notes, are most often produced when animals died in particular environments or circumstances, such as muddy marshes, where their bodies can be buried undisturbed to be gradually transformed to stone.

But human activity has drastically transformed fossil-friendly environments such as wetlands, which could reshuffle the circumstances under which fossils are preserved or not preserved. At the same time, human activity has produced vast quantities of new materials, such as concrete and plastics, some of which may be durable enough to become part of the fossil record for distant future civilizations to ponder.

According to Quartz, such “technofossils” may be more prevalent in the future fossil record than “traditional” fossils left by organic material. Indeed, notes Gizmodo, bits of plastic refuse are already being incorporated in a rocky material dubbed plastiglomerate.

Fossilized or Not?

On the flip side, a couple of factors could limit the impact of our own civilization on the fossil record. As Gizmodo also notes, our civilization is very good at digging things up and churning things up. Industrial civilization might eventually grind up its own potential fossil record before it ever has a chance to fossilize and be preserved.

Or, if present-day civilization wipes itself out, it might not last long enough to leave much trace in the fossil record for a future civilization to ponder over. As one paleontologist frames the question, “if we are geologic-scale agents, then are we leaving a record that could be found in the million-year time frame?”

It might be called the million-year question about the future of humanity.