The word ephemeral comes from a real animal. Mayflies belong to the insect order Ephemeroptera, from the Greek for a creature that lasts about a day. Naturalists needed a name for something that lives and dies inside a single evening, and they named an entire branch of the insect world after that fact.
Most people who have ever seen a mayfly saw it at dusk, in a mating swarm rising and falling over a river or lake. Adult mayflies do not eat. Many species do not even have functioning mouthparts. Their only task, in whatever time they have left, is to mate and lay eggs before they die, sometimes within hours of first taking flight.
For a handful of species, that window is almost absurdly small. Dolania americana, a mayfly found in rivers across the eastern United States, lives as a winged adult for less than an hour in some cases, occasionally just a few minutes. It is often cited as the shortest-lived adult stage of any insect on Earth.
For a year or more before that hour, the same animal was underwater, unseen, doing almost all of the living it would ever do.
How much of a mayfly's life do we actually see?
Mayfly nymphs spend anywhere from several months to two or three years on riverbeds and lake floors, depending on the species, feeding, growing, and molting repeatedly before they ever surface. That stage is not a prelude to the real life. It is nearly the entire life. The flying, mating adult that gives the order its name and its reputation is a rounding error attached to the end of something much longer and much less visible.
There are more than 3,000 known mayfly species, and the nymph stage varies enormously between them. Some spend only a few weeks underwater before emerging. Others, in the genus Hexagenia, can take up to three years to complete their development, spending nearly the length of a small child's entire life on a riverbed for a single day, sometimes less, in the air.
Fly fishers have built entire seasons around predicting mayfly hatches, since the emergence is so short and so concentrated that missing it by a day can mean missing it entirely for that year. Naturalists and poets have used the mayfly as a stand-in for brevity for centuries, almost always fixed on the one evening rather than the year that came before it. The unseen majority of the life rarely makes it into the metaphor.
That omission is not really a flaw in the metaphor. It is the metaphor. A sense of a life, or a species, or a civilization, tends to get built out of whatever happened to leave a trace. The part that leaves nothing behind gets treated as though it barely happened, even when it was, by any honest measure of time, the majority of what happened.
Mayflies are among the oldest winged insects on Earth, with a fossil record stretching back roughly 300 million years, predating dinosaurs by tens of millions of years. An individual mayfly gets a day. The lineage itself is one of the most enduring animal groups alive, older than almost anything else with wings.
Almost nothing about a mayfly's actual existence is the part anyone notices. The swarm at dusk barely registers against the year spent unseen underwater, and both of those are a rounding error against the 300 million years the order has already persisted.
What happens when the same ratio gets applied to us?
Homo sapiens has existed for roughly 300,000 years. Writing, cities, and anything resembling recorded history cover perhaps the last 5,000 of those years, a little under two percent of the whole. Go back further and the genus Homo stretches across something closer to two or three million years, a timescale on which our own species is itself a comparatively recent, comparatively brief chapter.
The shape of that stack, a long lineage, a shorter species-level existence nested inside it, and a brief, loud, visible final phase nested inside that, is not identical to a mayfly's. But it rhymes closely enough to notice. Nearly all of what made us who we are happened before anyone was writing it down. Language, cooperation, tool use, and the slow accumulation of everything a body and a mind needed to eventually build a city, took place across a span of time that left almost no record anyone could witness directly.
What we call civilization, the part with names, dates, and monuments, is closer to a mayfly's one evening on the wing than to the whole of the life that produced it. It is the part we can see because it is the part that happened to leave a mark.
If some future observer, watching from far enough downstream, ever caught a glimpse of us the way we catch a glimpse of a mayfly swarm rising off a river at dusk, they would be seeing the loudest, briefest, most visible sliver of something much larger and much older. Everything that actually built us would already be finished, underwater, out of view, long before anyone noticed the wings.