Frankly, if Serrana's evolution and biosphere don't look unlikely, I haven't done my job.

I'll explore the key stages in Serrana's evolution in order, since each affects the next:

VARIED SEAS

Each sea has its own temperature range and salinity and mineral balance, shaping the life within. The three biggest seas (Aburros, Narek, and the Eamet Ocean; see map) have variable salinity, as they reach from the high-evaporation equatorial zone to near-polar ice regions where surface water is nearly fresh. Strong salinity and temperature gradients give these three seas equally strong currents, both surface and deep (far shallower than Terran seas, but still deep enough for loops).

In contrast, the small seas, the Niirg, Leas, and Ice Sea each lie within one temperature zone, making currents weaker, and are too shallow for deep countercurrents; it's all on the surface. The Ice Sea is brackish, nearly fresh; the Niirg and Leas are warm, evaporate quickly, and are thus quite salty. The Leas borders on the great deserts, so it's dusty as well--loaded with nutrients. Desert above, riotous below.

The southeastern Eamet Ocean, downwind of the great deserts, also gets a lot of dust and supports rich plankton, but currents spread the stuff throughout the southern Eamet. Indeed all the seas have more dust and richer plankton than Earth. There are few biodeserts--the northern Aburros and Eamet do have less dust, but glacial silt pours down the rivers to take its place. All in all, nutrient shortages matter less than on Earth. Sea life is generally denser.

SEA-DRIFT

Humans are land animals mentally as well as physically. Consider: tectonic plates move, not continents alone; yet we denizens of these islands in a world-sea call this continental drift. The collision or isolation of continents does shape land evolution profoundly, but that only happens when you have a world-sea. Now Serrana has a world-land, which churns around but can't bud off isolated chunks of any size. Without continents, no continental drift. Less isolation, less speciation. What Serrana has is sea-drift! As the seas migrate, they crawl across the churning land into different climate zones, they collide and merge their biota, they divide like monster amoebas, and their creatures diverge.

This means life only had to evolve in one sea. After photosynthesis arose, the seas passed life on, intermittently. Even if it hadn't, within a few million years, meteor impacts splashed water between the seas, seeding them all with diatoms. Thus, unicellular life quickly went global, while multicellular life--big life--diverged regionally. And profoundly! The crawling seas underwent hundred-million-year experiments and passed the results on to the next sea. Like a child's game of "telephone", changes magnified and cascaded.

What to expect? Think of our Caspian Sea, ice-covered polar waters, isolated shallows like the Galapagos's marine iguanas, the jellyfish pools of Pulau, cave-pools. Not all seas need end up dominated by bony fishes as on Earth.

The northern Aburros Sea, with its gradient from arctic to tropical, has particularly strong currents and seasons, so migratory creatures and strong streamlined swimmers will have an advantage. Warmblooded fish, developing into sea-dragons?

The Eamet, relatively deep, will be the only sea to evolve giant squidlike benthic hunters as well as smaller shoreline hexapi. Another group will evolve a skeleton and be the equivalent of bony fish, but perhaps with six small lobe-fins or feelers, not four. Bugfish? Six-limbed vertebrates will have consequences later on--on land. Centauroid bodyplans will be common.

The small seas of Narek, Niirg and Leas are shallow, warm, salty, and often linked. There are no depths; large crustaceans dominate the coral reefs and estuaries, from which land animals emerge. Let's make them quadrupedal, to contrast with the hexapodal vertebrates and molluscs... Quadrupedal, but effectively five-limbed: a snout-claw. Why not? Even in our symmetry-mad world, look how many crabs have one big specialized claw!

ONTO THE LAND

Pioneers from each sea, with different body plans, crawl onto land, finding various solutions to the leg problem.

From the Aburros Sea came Earthlike amphibians, slowly evolving into proto-dinosaurians. The early body-plan was quadruped, but is now bipedal, freeing forelegs for hands. Scaly raptors and "kangaroos" evolved feathers... Interestingly, they all have marsupial pouches.

In the Lesser Seas, crustacean quadrupeds with snout-claws start climbing trees in mangrove swamps. Soon the claw becomes a branch-grasping hand. Tree-elephant-crabs? Land species eventually shed (so to speak) the molting process--too vulnerable. The exoskeleton gets covered in skin; bathed in nutrients on both sides, it can grow steadily; no need to molt. Eventually coarse fur, almost like tree bark, covers these elephant-crabs. Odd though it sounds, these are the ancestors of Serrana's largest land animals: the mammoths.

The Eamet Ocean's double contribution: tidepool hexapi (like octopi, but six-legged) evolve into arboreal land-squid. Bonier hexfish in estuaries become lobefins and, eventually, centauroids, browsing the forests and grasslands with their forearms while keeping four feet on the ground... Some centauroids grow large and furry: "equines" and "antelope" on the veldt and "llamas" on the planos, all with hands. Others stay small but develop feathers; these flying quadrupeds range from small but quite mammalian-looking pegasii to more birdlike griffins and dragonets. The extra limbs add dexterity but also weight; they compete with the better-flying but less dextrous two-legged birds spreading from Aburros, but neither group dominates all niches.

On Serrana there are two phases to the land invasion, and many species only manage half. Almost all early land creatures emerge into rainforest or swamp, but most of Serrana is dry--grassland, steppe, tundra and desert. Now, species who linger by the shores and in tropical forests stay comfortable--and local. But those who step out of the trees can spread worldwide. True, it's a tough veldt out there: you face creatures that might as well be from different planets.

ON BODY PLANS

On Earth, big land creatures are all biped or quadruped. Tripods never evolved, pentapods (echinoderms) stayed marine, and legless forms (snakes), unipods (snails), hexapods (insects) and octopods (spiders) are numerous, but small. But the size limit is due more to insects' and arachnids' breathing problems than any obvious disadvantage due to leg arrangement; again, consider giant squid in the seas!

Let's reverse the situation, then, in Serranian seas: in their shallows, hexapods or octopods with jointed legs, either exo- or endoskeletal, develop efficient lungs and grow large, while quadrupeds mostly remain small. A centauroid body plan has advantages in open woods and savanna: fast locomotion but safer grazing--your hands can harvest food from brush, trees or even grass while your head stays up, alert. On wide prairies two or four legs seems adequate. Fewer berries and high leaves to harvest, and it's easier to spot predators, even with your head down, when there's no cover. Consider the land where roos survived: dry, isn't it? Pure coincidence, you say? Consider ostriches! Veldt or forest? I won't insist on the point, but...

WHAT BODYPLANS FAVOR INTELLIGENCE?

Earth's standard avian and mammalian body plans are quite awkward for intelligent species--hands must double as feet! To hold a tool or examine an object, apes like us must sit or totter around on hind legs. Ravens must either grasp with their beaks or balance on one foot. There are solutions, of course: human bipedalism is just a makeshift version of a plan kangaroos and velociraptors worked out long ago.

But freeing up hands is a quadruped problem. Four limbs aren't the only way! Elephants nosed out an elegant solution, and crablike Serranian mammoths have done the same. And why stop at five? Many Serranian groups favor six. Centauroids have enough limbs to let (four) legs be legs and (two) hands be hands. Squidlike creatures, like apes, needn't allot a fixed number of legs for propulsion versus manipulation; but unlike apes their tentacles can be a spectrum, from delicate to sturdy. A limb for every purpose--like a living Swiss Army knife!

So on Serrana, omnivorous roos and small dinos living in equatorial forests may fan out into the huge Serranan veldt, picking up rocks and tossing them, playing with fire... to discover centaurs and land-squid from across the deserts, cameloids in the mountains, hand-snouted crabs on the tundras...

RADIALITY

Picture a sea dominated by squid in the depths (after all, this was the pattern in Earth's seas until the recent reentry of large mammals, in the form of sperm whales) and octopi in the shallows. Octopi already crawl out of the water when it suits them, even under one full gravity; so land octopi are a plausible consequence of low gravity and molluscoid dominance of a sea. But eight legs is arbitrary (as squid prove); let's make Serrana's form six-legged. Some begin to climb into trees in "mangrove" swamps, like Terran tree-crabs. The start out amphibious but at last adapt fully to the air, and fill the niches apes fill in our rainforests. Tree-squid! But will they stay mere molluscoid apes, or learn tool use? Their language might be pictographic, color glyphs rippling over their skin. At first literal, concrete pictures, these will eventually simplify and stylize into a written language with abstract symbols--but no spoken form. It's hard to imagine, but picture a hybrid of Sign with... cartooning?

Eons later, at the forest's margins, a few leathery, sun-tolerant squid step onto the savanna... as we did. Earth octopi are smart--will the hexapi learn tool use, fire, language? Their language might be pictographic, color glyphs rippling over their skin, or would they lose their chromatophores as their hides thicken to prevent sunburn? Or they might further develop sign language--hexapi have free limbs to gesture while still walking and carrying tools and kids with others. Less need to develop our specialized nerves and muscles for speech. Would they have voices at all? Would they develop purely instrumental music? Consider the Darwinian advantage of a band with a hexapod drummer!

ON THIN AIR

We forget that Earth is an extreme environment in one respect. Our air's the thinnest of all the large worlds in our solar system; Venus and even little Titan have more. What would Earth be, if we had, say, double or ten times our current atmospheric pressure? Unlivably hot? We don't know that! Earth has survived much warmer conditions in the past. Yes, Venus died, but it had twice our insolation and ONE MILLION times our CO2 level. Of course, life (or at least liquid oceans) absorbed much of ours--primal Earth's air was CO2-rich too, and possibly much denser. Still, my basic point is that few Earth-sized planets with life will have air pressures one-tenth of ours--but many may have much thicker atmospheres. And that increases the potential number of living worlds:

1. If a world's habitable at all, most of it will be. Thin-aired worlds like ours can have wide sterile belts--like our desert zones and polar caps. Such temperature belts are much evener on thick-aired worlds. Venus's poles and equator are equally hot, unlike the Terran/Martian patttern.
2. Also, with thick air to distribute heat, slow-spinning worlds or worlds with extreme orbital tilts may be still viable even if large parts of the planets face long dark nights--or winters.
3. Thick-aired worlds, with their stronger greenhouse effect, can orbit further out, effectively expanding the the zone in which water is liquid (and life can evolve). This doesn't automatically increase the number of such worlds--the match between atmosphere and orbit is still a matter of chance, and thick air can overheat worlds at the inner edge of the zone as well as save ones on the outer edge--but rigid formulas declaring outer solar systems totally sterile are premature. Small red stars, for example, were traditionally written off, since their liquid-water zone was so close that tide-locking becomes quite likely. But thick-aired worlds could orbit further out, where tidal drag's less of a problem. Even if most small stars are likely to have equally runty planets, a minority will have an Earth (or a Neptune) in this outer life-zone. And such stars are so common that we're talking a LOT of worlds...
4. Multiple worlds in one system can be viable, if by luck a thick-aired world or two have outer orbits while thin-aired ones huddle close to the sun. If life evolves on any one world, meteor strikes will spread it to others where it might not have evolved but can survive, adapt, and flourish. It's quite possible that optimal birthplaces for life and ideal biospheres (big, diverse biomass, complex forms, intelligence) are quite different. That could even be true of us--it now looks possible life evolved on Mars and spread to Earth (admittedly, Earth's abyssal rift gardens are also strong candidates for biogenesis).

Does air pressure affect the evolution of intelligence? Yes. On thin-aired worlds, the weight limit for flying creatures means that intelligence is limited to swimmers and walkers. Pound for pound, the smartest brains on Earth are avian, and while it's probably possible to bioengineer a flying person--a pygmy angel or a giant raven or parrot, take your pick--but such forms are unlikely to evolve in the wild. They're just too close to Earth's weight limit for easy flight, currently about 20 kilos. The fact that Earth birds are as smart as they are suggests that life in the air stimulates the mind: 3D acrobatics, the sheer stimulation of travel between varied ecozones, the need to memorize landmarks and navigate intelligently, and especially the stimulation of social contact over long distances. I'd add one less obvious feature of life on the wing. "Birdwatching" is popular among mammals (not just humans--think of cats!) because birds are uniquely visible. They can afford to be--on the wing, nonfliers just can't attack them. But the reverse is also true--so true we hardly notice that birds are mammal-watchers. They constantly observe life below them--not just for food or safe perches, but for sheer entertainment. Birds are voyeurs. We're spread out below them; they witness the survival strategies of many species. Intelligent birds learn from those strategies. Flying, in short, is educational. Such a rich information environment favors clever, social, observant, opportunistic generalists, and that's just what parrots and corvids are--up to the limit air-pressure imposes!

I conclude that thick-aired worlds can and will have flying intelligences. Conversely, thin-aired worlds like Serrana and Earth, with low weight-limits for fliers, won't. Serranians may swim or hop or gallop or swing in trees, or rollerskate for all I know... they may be bilateral or radial, biped, triped, quad- or hexaped, but... they won't fly.

Of course, as Serrana's flying foxes show, I could be wrong.

RED AND BLUE BLOOD

Creatures evolving in some seas may tilt toward iron-based or copper-based oxygen transport. Are there other possibilities? At least one sea should go with copper so we have blue-blooded arthropods dominating the sea and colonizing land. Land-crabs? Land lobsters! No obvious size limit, if they develop true lungs and hinged carapaces letting them breathe freely. Though copper's less efficient, so in Serrana's thin air, the bluebloods might be restricted to lowlands. Of the species I'm planning, the land-squid fit best; the "mammoths", though ex-crustaceans, will specialize in mountain environments as well as polar tundra; in Serrana's thin air, they'll need hemoglobin on some equivalent--copper won't make it. So their sea must have been one rich in iron dust; that means near the Tsud. Though the only known rich copper deposits are in southeast Tsud as well--it was mined and mentioned on the original Anarres, in Le Guin's DISPOSSESSED; and since Serrana is a tribute to that book, I have to honor that. Hence the copper-based land-squid I plan will probably evolve from the Eamet Ocean, east of the Tsud, while the iron-based mammoths arise from the Niirg or Leas Sea to the west.The Narek Sea is more Terran--lower dust levels--and might spawn earthlike amphibians at the warm south end, who spread west through the jungle--to eventually (MUCH later) release a wildfire on the world: dinosaurian raptors.

COMPETITION AND COOPERATION

Ever read Kropotkin's studies of animal cooperation? His fieldwork was in Siberia, not the kinder climates Darwin observed. Kropotkin concluded that for most creatures, most of the time, the real enemy isn't the neighbors, but the environment. Social cooperation pays off more than competition. Serrana is certainly poorer than Earth. In its sparse biosphere, whose paradigm will dominate?

Maybe the type of land also matters, not just its overall harshness. I wonder... is our human focus on competition and predation one result of the savanna our ancestors evolved on? Consider: on a veldt, there's lots of solar energy trappable by life, but it's available to animals in only two forms: grass, or grass-eaters! You belong to one of two hard-working parties--red or green, predator or prey. There just isn't room for much else--no fruitarians or leaf-eating apes, as in the forests. No Darwinian slackers on the veldt!

It's a cliche that once tool use began and we could crack bones and/or hunt effectively, rival species of people couldn't evolve; we'd pre-empted the new niche and would defend our new food source. But is it true? And even if it was true on Earth, must ALL technological peoples EVERYWHERE go through an early hunting phase, does this foster the coordination and dexterity needed for a tool-based cvilization? Is this why elephants never developed tools, despite brains, social skills and "hands"?

But alternate theories of even our own origins abound. Bob Brain has argued that our minds were shaped by fear of predation by big cats, and that fire and tools and war began not in the hunt, but as defenses against monsters that came in the dark to eat us. So is hunting the only path to intelligence, or is fear the spark that lights the fire? Again, the elephants hint he could be right. Why raise the club, or torch, or spear? No need--no one to fear.

Now Serrana is harsh, with thin air, deserts, and sparser life than Earth. But though the colder parts of it are much like the Siberian ecology that inspired Kropotkin, much of the fertile equatorial zone is veldt, and veldt with far more diverse creatures than Africa, creatures from all over the world and several different seas--molluscs and crustaceans walking around next to dinos and mammals. With a wider pool of pre-sentients (creatures with dexterity, large brains, social groups, protolanguage) must they all compete over one niche--the prehuman hunting path? Are there elephantine alternatives? More to the point, non-elephantine alternatives?

What large predators will roam the veldt? At first, tooth and claw may rule, but my guess is that if I'm allowing one sea to develop birdlike dinosaur analogs, we'll eventually get stone-age raptor bands hunting the dusty plains. Terran velociraptors WITHOUT tools were scary enough--tool-using raptors will quickly become top predators, and cause mass extinctions, both of favored prey species (the largest grazers) AND any rival predators dumb enough to attack tool-users, or compete for their favored prey. Some paleontologists still doubt that the Australian and American mass extinctions were human-caused, but I'm in Jared Diamond's camp on this one; I'm certain that the first Serranians to tame fire and sharpen spears will cause a worldwide extinction wave. The only real question is, will they commit genocide as well? Will they fill the niche and eliminate rivals, or is Bob Brain right? With so many intelligent species around, will the fear of raptors produce other tool users, spark imitative tool use in other species (remember they all have hands) just to survive? A prehistoric arms race--because Serranian species had more arms.

Sorry. Couldn't resist.

This brings us back to Kropotkin. How quickly will contending intelligent species shift from Darwinian competition to cooperation? Empathy and morality applied across species is still rare among us; but no intelligent tribe in our world failed to learn eventually that raiding armed neighbors is risky and treating them as meat is just suicidal. But how long is "eventually"? Will an early era of species war shape Serranian minds, as ours were shaped (if Bob Brain is right) by our long period as prey to big cats? Or would multispecies war quickly settle to some modus vivendi, leaving little mark? Predator/prey relationships are profoundly unstable when all parties are self-aware and may act on imagined futures, not present animal needs. What's the optimal strategy when your "prey" may turn and hunt you--not from hunger or anger, but from a plan to remove your menace for good, or to teach you a lesson--to shape your mind?

In short, once mind awakes at all, competition may quickly shift to inner space: no longer a competition of organisms or genes but of ideas. Game theory suggests cooperation is the stablest game, after a tit-for-tat learning period--punishing misbehavior, if not consistently rewarding cooperation (that may follow; it's called trade). Let's say there's a jerk at the party--a species refusing to leave other tool-using tribes alone--say, an aggressive, exclusively carnivorous early raptor (notice how us mammalian writers always demonize dinos rather than admit it's us?) It'll provoke its neighbors to unite and punish it--something only future-thinking animals will do. Its legacy will be a league.

The peaceful result of all this may sound more like the Shire than Kropotkin or Darwin, but the struggles leading to cooperative equilibrium may have been long, harsh, or both. If my scenario looks naive, remember we're bred to be cynical! We were shaped by millions of years of struggle with big, toothy, stupid foes, and a much shorter period in which to learn that armed neighbors can retaliate in kind. Serranians had to learn tolerance early, from all directions: all surviving species make a sharp, instinctive distinction between "animals", which may be ignored or tamed or eaten, and "people" of any species, to be treated politely--or else. It's as instinctive as our primary distinction, still seen in children, between ordinary animals and monsters: creatures that stalk us. Our deep past haunts us, but we don't question the shape of our minds. Nor do Serranians.

You'll note I said all surviving intelligent species. Did you assume none went extinct? Or, to be more accurate, were driven extinct by other species who could co-exist! On Earth, Dinofelis apparently ate our ancestors, but in this, the only known bout between monster and lunch-with-tools, the lunch won. So it was on Serrana, too--but the struggle was multisided, and cooperators survived the best.

Earth, too, has lots of species lacking just one of the crucial five traits needed to become civilized:

1. big brains
2. sociability (giant squid and orangutans are bright but may be too solitary to develop civilizations)
3. language
4. hands (or other means to manipulate the world)
5. an environment with raw materials for tools and fire (tundra and deep sea are poor in this regard).

On Serrana, in contrast, Darwinian brutality was itself selected against. Even on Earth, this does happen, though more slowly. Evolution's hard to see in a single lifespan, but the Kropotkin-Darwin debate's not over yet. Le Guin's THE DISPOSSESSED, is, after all, precisely about anarchism's advantage in difficult times and places--voluntary cooperation, with all its complexity and delays, beats the brute simplicity of archism. I'm just extending her model beyond Emma Goldman's human anarchism to Kropotkin's biological theories--past the question of how one species can live with itself, to how species cooperate with others. Our solitary climb to civilization may not be the only way; scarred by a scary past, we may be biased, limited, pessimistic.

But Serranians can't afford to be.

See PEOPLES OF SERRANA: a bestiary--no, a sentiary, a chart of sentient species on Serrana, plus a description of the causes and effects of a multispecies society.

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