(How she wished it could be a two-way joining. But save when they were together in the flesh, they could merely speak back and forth, via a bone-conduction unit. Nevertheless, they were oath-sisters in truth. They were!)
“It’s not telepathy,” she said. “The channel won’t carry but a tiny fraction of the total information. Most of what I experience is actually my own intuition, filling in the gaps. I’ve spent my career training that intuition. I’m trying to discover how accurate it really is.”
“I understand,” Flandry replied. “And you aren’t linked continuously, or even as much as half the day, as a rule, let alone your absences from the planet. Still, you’ve been very deeply involved with this being. Your chief purpose has been to learn how to feel and think like her, hasn’t it? Without that, there can be no true comprehension. So of course you’ve been affected yourself, in the most profound way.”
They sat down on the rubbery deck and leaned against the bulkhead, side by side. “And therefore I won’t know you, Banner, before I know more about Yewwl,” he said. “Will you tell me?”
“How?” she sighed. “There’s too much. Where can I begin?”
“Wherever you like. I do have a fair stock of so-called objective facts to go on by now, remember. You’ve taken me well into the biology—”
Although the Ramnuan atmosphere resembles Terra’s percentagewise, the proportions of the minor constituents vary. Notably, we find less water vapor most places, because of the pressure and temperatures; more nitrogen oxides, because of frequent and tremendous lightning flashes; more carbon dioxide, hydrogen sulfide, and sulfur oxides, because of vulcanism. These would not be what killed us, if we breathed the air directly; they would simply make it acrid and malodorous. What we would die of, pretty soon, would be oxygen and nitrogen. They are not present at concentrations which are intolerable for a limited span, but their pressure, under seven gravities, would force them into our lungs and bloodstreams faster than we can stand. Incidentally, that pull by itself forbids us to leave our home-conditioned base for any long while. Our cardiovascular system isn’t built for it. Gravanol and tight skinsuits help, but the stress quickly becomes too much.
Just the same, Ramnuan life reminds us of our kind in many ways. It employs proteins in water solution, carbohydrates, lipids, and the rest. The chemical details vary enormously. For example, the amino acids are not all identical; since weather provides abundant nitrates, “nitrogen-fixing microorganisms, while they do exist, are—like Terra’s anaerobic bacteria—archaic forms of rather minor ecological significance; et cetera endlessly. In a broad sense, though, evolution has followed a similar course to ours. Here too it has founded a plant and an animal kingdom.
The critical secondary element is sulfur. It is so common in the environment, thanks to vulcanism, that biology has adopted it somewhat as Terran biology has adopted phosphorus. On Ramnu, sulfur is vital to several functions, including reproduction. It is usually taken up by plants as sulfate, or in the tissues which herbivores and carnivores eat. Where an area is deficient in it, life is sparse. Forest fires help, redistributing it in ash which the dense atmosphere disperses widely. Most important are certain microbes which can metabolize the pure element.
When it becomes freshly abundant, as around an active volcano, these organisms multiply until sheer numbers make them visible, a yellow smoke in air, a hue in water. Dying, they enrich the soil. This is the Golden Tide whose coming has brought fertility to land after land, whose dwindling has brought famine till populations died sufficiently back. The natives also transport sulfur, on a far smaller scale; their trade in it has conditioned their histories more than the salt trade has those of humans.
Given the oxygen concentration and the incidence of lightning, fires kindle easily and burn fiercely. Outside of wetlands, such a thing as a climax forest scarcely exists; woods burn down too often. Vegetation has made various adaptations to this, deep roots or bulbs, rapid reseeding, and the like. Most striking is that of the huge, diverse botanical family which we call pyrasphale. It synthesizes a silicon compound which makes it incombustible.
The pyrasphales have numerous analogies to the grasses of Terra or the yerbs of Hermes. They are comparative latecomers, that have taken over the larger part of most lands and proliferated into a bewildering variety of forms. Many do bear a superficial resemblance to this or that grass. Their appearance was doubtless responsible for a period of massive extinction about fifty million years ago; they crowded out older plants, and countless animals could not digest their fireproofing. Later herbivores have adjusted, either excreting it unchanged or breaking it down with the help of symbiotic microbes.
Pyrasphale has not displaced everything else. Where it reigns alone, that is apt to be by default. Ordinarily, a landscape covered by it has stands of trees, shrubs, thorn, or cane as well.
The animals of Ramnu exhibit their own abundant analogies to those of Terra, including two sexes, vertebrates and invertebrates, exothermic and endothermic metabolisms. The typical vertebrate has a head in front, with jaws, nose, two eyes, two ears; it bears four true limbs; commonly it sports a tail. But the differences exceed the likenesses.
Among the most obvious is the general smallness, under that gravity. Outside the seas, the very biggest creatures mass a couple of tonnes; and they inhabit regions of lake and swamp, where the water supports most of their weight as they browse around. A plain may teem with herds of assorted species, but nearly every one is dog-sized or less. An occasional horse-tall beast may loom majestic above them. It has a special feature, of which more later. Otherwise, at first it strikes a human odd to see a graviportal build on an animal no bigger than a collie. The gracile forms are tiny.
The long, cold nights set a premium on endothermy. Exotherms must find a place to sleep where they won’t freeze (or, they hope, be dug up and eaten) or else start a new generation by sunset whose juvenile stage can survive. Plants have developed their own solutions to the same problem, including a family which secretes antifreeze and several families which make freezing a part of their life cycles.
An intermediate sort of animal has a high metabolism to keep warm at night but—outside the polar regions and highlands—must take shelter by day, lest it get too warm. Complete endothermy is harder to achieve than on Terra, since water evaporates reluctantly. The larger animals grow cooling surfaces such as big ears or dorsal fins. Flyers face less difficulty in this regard, for their wings provide those surfaces; but it is worth noting that none have feathers. They are abundant on Ramnu, where the gravity is more or less offset by the thickness of the atmosphere. The swift drop of pressure with altitude does make most of them stay close to the ground. A few scavengers can soar high. Then there are the gliders; but of these, too, more later.
Among the land Vertebrates, an order of viviparous endotherms exists which has no Terran paralleclass="underline" the pleurochladoi. Between the fore- and hindlimbs, a pair of ribs has become the foundation, anchored to an elaborate scapular process, of two false limbs, which humans call extensors. It is thought that these lengths of muscle originated in a primitive, short-legged creature which thus found a way to hitch itself along a trifle faster. The development was so successful that descendants radiated into hundreds of kinds.