+An interesting fact discovered. At one time, oh dear, dear, how long ago, the base of ten was universally used. It was replaced by twelve, undoubtedly because of its superiority. So it appears that the finger theory must be dismissed+
+Not at once. My researches have disclosed that at one time a large proportion of mankind had but ten fingers+
+A coincidence+ Dehan did not believe the words even as he spoke them.
+Possibly. But if there is an explanation — what is it? If the two facts are interconnected the resulting logical equation can be read in one of two ways. When the shift from base ten to base twelve occurred there was a resulting change in the number of fingers+
+Highly improbable+
+I agree. Therefore we must consider the alternative that some great mutation, change, or conflict swept the human race. Perhaps there were Opposing groups and the twelves won over the tens in a great war…+
+There has never been a war like that. I would know+
+Of course. But it is an interesting problem+
They sat in silence for a while, sipping their drinks and watching daylight come to the valley below them. The morning fogs burned away as the first rays of the great orange sun struck through the mountain crags. There were crude dwellings beside the river and Dehan touched the window controls. Instantly the image expanded, so enlarged they appeared to be right in among the huts. A blue-skinned aborigine waddled through the doorway, yawning long saurian jaws to show impressive rows of pointed teeth. It picked up a stick and dug at some irritation in the deep folds of skin while looking on coldly at the growing activity around.
+Time bound+ Linkica said. +We were once that way, too. The ontological evidence is clear+
+I do not know what you are referring to+
+These creatures. Their life cycles are bound to the planetary rotation. They sleep during periods of darkness and are awake during their day+
+How unnatural+
+Not at all. It is the natural outcome of a planetary existence. It has taken us thousands of generations to outgrow our dependence upon a waking-sleeping cycle, to reach the present point where we sleep for short periods whenever we feel tired+
+I can imagine no other way to sleep. And if this change were made, what possible reason could there be for it?+
+That appears obvious. The Doors. Their introduction must have altered every facet of existence+
Dehan raised his eyebrows. +Then you are not one of those who believe that the Doors have been with us from the dawn of time?+
+A child's myth. The Doors are artifacts that we still build. Though now they are single unit, solid block, solid-state construction, almost indestructible, they were not always that way. Earlier forms can be found in museums. Have you never wondered why there are always two Doors together, always?+
+I never considered. It is just the natural way of things+
+There is a reason. An engineer told me. Perfect as the Door mechanism is there can be, once in a very long while, a failure of mechanism. If this happens the other Door is always standing ready. There are many places where it would be embarrassing to be without a Door+
+Indeed!+ Dehan said and felt cold at the thought, thinking about his room. It was embedded in the solid rock of a world whose name he forgot. He had never been on its surface because it was airless. At one time it had been mined for precious metal, and great tunnels were driven through the heart of the stone mountains. When the ore was gone the tunnels had been plugged with molten slag. At intervals. Doors had been left in the boxlike openings to be furnished as private quarters. Very private. Without the Doors they were but bubbles in the rock. It would be a lonely, forgotten death for anyone trapped in one of them.
+Logic forces us to a single conclusion+ Linkica said. +There must have been a time, unimaginable as it is to us, when mankind did not possess the Doors+
+It follows then, that you are a monolinearist, not a multifontist?+
+Of course. For one thing it is biologically impossible to have a single species occur in a number of different places. and then be able to interbreed. Just as there was a time when we had no Doors, so was there a time when we were confined to one restricted area of space+
+To but a single planet?+
Linkica smiled. +You said it — I did not. It carries the theory almost too far+
+Why? I do not tempt you into rash statements for I am as enthusiastic a monolinearist as you are, even though it is an unfashionable attitude to hold these days. I will go even further. I believe we did originate on a single planet at one time. Just as those creatures out there are natives of this world and incapable of leaving+
+You force agreement from me. I admit to physical change, but never considered that cultural change must accompany it. We may have originated from as crude a background as this one. If so — it had to be a single planet+
+I have long thought so, and during my work have traced mankind's movements backward as far as possible. Always I have found the simpler growing into the complex. My researches have been exhaustive+
Linkica shielded his eyes for a moment in the sign of great appreciation. +Can it be that you have discovered this proto world, this home world?+
+Perhaps. Though I doubt it. I have traced back all records, the oldest records, to an incredibly ancient world. I do not know if it is the planet, only that there are none older+
+I humbly request the code+
+A pleasure to share it+ Dehan spoke the digits aloud. +In fact we could go there now and see it+
+You are kinder than I thought possible+
+I am pleased to take you. So few show any interest at all+
Dehan led the way through the Door to a small and crudely furnished room.
+So rarely do people come here that it is sealed for the most part. See my visits on the graph. The first in many thousand units+ He examined the controls and nodded with satisfaction. +Air, temperature, all is well+
They passed through a sealing door into a long, corridorlike room. There were viewing ports set into one wall while everywhere else were cabinets and displays.
+Dead now+ Linkica said, looking out on the desiccated landscape. A sun, scarcely brighter than the other stars, shown as a cold, unblinking disc in the black sky. Air gone, water gone, life gone, bare sand and rock stretched flatly to the horizon. Yet nearby great monoliths, fissured and eroded, still bore witness of having been shaped by some intelligence.
+These cases contain the few identifiable objects found here+
Linkica turned with a high anticipation that slowly faded and died.
+These could be — anything+ he said, pointing to the eroded lumps of metal and stone.
+I know. But should we expect more?+
+Of course not. You are correct+
Linkica looked once more at the mute age-old shapes, then out again at the dead plain. He shivered, although the room was warm and comfortable. +I feel the weight of ages here. More time than I can possibly understand has passed for this world. I see how short my own individual span of existence is and how unimportant+
+I have felt the same thing myself, here, many times. It is said that a man's mind cannot encompass the idea of its own death, but when I am here I can begin to see how a species might die. If we had not had the Door we would be here, trapped here, dead here, if this were the only world we had ever known+
+Give thanks it was not. Mankind is universal. We rule everywhere+