Severian, the narrator of Gene Wolfe's The Sword of the Lictor , describes his descent of a cliff:
The past stood at my shoulder, naked and defenceless as all dead things, as though it were time itself that had been laid open by the fall of the mountain. Fossil bones protruded from the surface in places, the bones of mighty animals and of men. The forest had set its own dead there as well, stumps and limbs that time had turned to stone ….
Deeper than these lay the buildings and mechanisms of humanity. (And it may be that those of other races lay there as well ….) I saw …. colored metals so curiously wrought that I could not be certain whether their shapes had been intended as works of art or as parts for strange machines ….
This is a direct stab by the author at piling on the idea of a culture layer – a layer of physical evidence, of stuff , left by all the civilizations that ever covered the area in question. Gene Wolfe is writing about the very far future, when the Sun itself is old and dying, and Earth's history is far closer to its end than to its beginning. When you think of how much man-generated stuff of all kinds there already is on the world's surface, and when you think that history might continue for millions of years, you realize that we are most likely accumulating something big. (A shorter tale, evoking such accumulation, is Clark Ashton Smith's "The Planet of the Dead".)
A related point is made humorously by Jack Vance in The Eyes of the Overworld . This, like Wolfe's tale, only even more more, is set in Earth's extreme old age. Drinkers in a tavern are arguing about the validity of the doctrine held by the Funambulous Evangels, who
"…. stipulate that for every square ell of soil two and one quarter million men have died and laid down their dust, thus creating a dank and ubiquitous mantle of lich-mold, upon which it is a sacrilege to walk … . The total therefore represents almost one mile of compacted corpse-dust mantling the earth's surface, which is manifestly false. "
The critic goes on to explain that if the doctrine were true, the seashore would be lined with cliffs of corpse-dust a mile high. A Funambulous zealot retorts that the "moistness exhaled and expelled by innumerable men of the past" has "raised the ocean an exact equivalence, so that no brink or precipice can be noted".
The practical result of the Funambulous Evangel doctrine is that its adherents must, out of respect for the dead, "walk aloft, on ropes and edges, and when we must travel, we use specially sanctified footgear."
The idea of a culture layer takes on a more seriously cultural (in the normal use of the word) form in Cordwainer Smith's "Alpha Ralpha Boulevard". I think that if I had to choose one Cordwainer Smith tale as his best story, this would be it. Science fiction doesn't get more haunting than this. Here again we are in the far future, though thousands rather than millions of years ahead; far enough anyhow for a tremendous sense of elapsed time to be conveyed by the author's skill. The exquisite paradox of the story is that the more those far future folk try to reconstruct their lost past, the more they make us feel the immensity of the distance between our time and theirs.
Virginia and I bought the first French newspaper to appear since the Most Ancient World fell. We found delight in the news, even in the advertisements. Some parts of the culture were hard to reconstruct. It was difficult to talk about foods of which only the names survived, but the homunculi and the machines, working tirelessly in Downdeep-downdeep, kept the surface of the world filled with enough novelties to fill anyone's heart with hope. We knew that all of this was make-believe, and yet it was not. We knew that when the diseases had killed the statistically correct number of people, they would be turned off; when the accident rate rose too high, it would stop without our knowing why. We knew that over us all, the Instrumentality watched ….
The people of this epoch, known as the Rediscovery of Man, yearn for authenticity, are hungry for risk. They and their ancestors were coddled for thousands of years in an meaninglessless culture of material well-being and spiritual vacuum. Now they want to feel they are living real lives like the ancients used to do – like we do in our time. Exploring the question of in what sense there can, and in what sense there can't, be a going back, Cordwainer Smith evokes the grandeur and contrasts and poignancy of a huge span of history, and makes us feel that we ourselves are mere dawn -age pioneers, hardly yet started upon Time's immense road.
The Ooranye Project, currently underway, is designed to convey the sense of a culture layer of a world whose civilization is 1.2 million years old. Even this span of time has not resulted in a layer that covers a large percentage of its immense surface, but with regard to historical memories the culture layer is certainly thick; the wilderness spaces ring with the recollection of victories and disasters. The twenty-five great disc-on-stem cities date from early on, having been built in the brilliant Phosphorus Era over a million years ago. The monorail system is somewhat more recent, but still ancient – it dates from the Zinc Era. The sequence of eras itself is a kind of mental artifact, as age follows age, named after successive elements in the periodic table, part of the mental furniture of Uranians. The story-heritage accumulates with the deeds of great adventurers and rulers, and human civilization in general, always threatened and outnumbered by other forces, is perhaps gradually inching towards a firmer foothold.