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Early Evolutionary History of Orwell, The

Evolution during the earliest periods of life on the world Orwell

Darwinian period on Orwell
Image from TSSL and Steve Bowers

Key to Illustration:

To the upper left is a Reteramus. the big floating tangle without much internal structure variety.

To its right is a Flat Chushou, which seen from the side; this creature is quite wide, and the two appendages at the top are its wings, which would be extensive if seen from above or below. The five appendages are its tentacles (of which another is hidden on the other side).

The Flat Chushou is nibbling on a Balloon.

To their right is a Skeletoforma; you can see where the individual petal-bodies meet; in this particular species, each petal-body has two eyes and, in front, a gill patch. The fin-bodies in back also each have an eye.

To the far left of the middle is a Headfang. The wavy features are gills. It is about to ram into the creature to the right.

To its right is a Petaloforma. It has three-way rotational symmetry as well as being identical in front and back. Each of the petal-bodies in ths species has an eye and a mouth; the central body has six eyes, with only two visible, and a mouth on each end (also serving as anuses), just slightly visible between the petal-bodies. The rows also have gill-grooves in them, and indeed the respiratory function is more important than the transportation one. The petal-bodies would be moving in and out, and could often be held together so that the creature would have an overall tube shape. (Fortunately, even if the Headfang eats one of the bodies, the Petaloforma can grow it back.)

Just above that is a Flimsy.

To the far right of the middle is a Reteramus of the more complicated variety. It has a pair of fins on either side consisting of branches supporting a membrane, with a filter-feeding net in front (its right) and various other branching appendages for grabbing, sensing chemicals and vibrations (it lacks eyes), as well as a few that can serve as legs when walking on the sea floor.

To the bottom far left is an Armored Ediacaroid of a coiled variety. The dots are holes which allow water and organic material to enter.

To its right is a Quadruforma; you can see that the main bodies are the four leg-bodies, each with a mouth on the far end, and you may also notice the compound eyes.

The Quadruforma is investigating another Armored Ediacaroid. This one features feathery appendages for respiration and filter-feeding, but is mostly inside its shell.

Just above that, a Shell Chushou is descending to avoid the Headfang. It has a ring of fins and a ring of six tentacles.

To their right is a reef of Spongiapublicans. This is a variety which uses spines on the outside for support. You can see a number of polyps growing around each other and inside each other, as well as a free-swimming polyp which is likely on its way to found a new colony.

On top of the Spongiapublicans is a small Brancher of the sort that build webs. It stands on a web which it has secreted between two of the polyps.

A Segmentaforma crawls through the colony.

To their right and a little above is one of the old-style Multacorpora. This one only has two subsidary bodies, held out in front, and still features traditional cilia rows and eye spots.



Evolutionary Timeline of Orwell

Orwell is a Garden World orbiting a K-class star in the Chronos Cluster, a world with a naturally evolved biosphere. Orwell is nearly two thousand light years from Sol. The geological history of this world is divided into numerous periods, named after various worlds in the Terragen Sphere, which currently resemble in some ways the conditions on Oewell at that time.

The NovaTerran Period

(named after Nova Terra, originally a lifeless EoGgaian world)

Starting with Orwell's formation eight billion years ago lasting several hundred million years, before the first life. Characterized by heavy bombardment, intense volcanism, the outgassing of a thick carbon dioxide atmosphere, narrowly avoiding a runaway greenhouse, and the formation of a world-spanning ocean.

The Eostremonathan Period

Named after Eostromonath, which had anaerobic life and was similar to Orwell in this period before terraformation)

Life on Orwell originated soon after the surface became stable. For a long time it was strictly prokaryotic and heterotrophic. Volcanism and temperatures were still high, so much of the life was thermophilic by Earthly standards. A wide-ranging group of heat-loving organisms developed chemosynthesis using specialized organelles. As they diversified, more organelle types developed to break down a variety of chemicals, including those in other organisms. By the end of the period, one chemotrophic subgroup developed a nucleus-equivalent from a series of interconnected chemical-generating organelles, repurposed to manufacture the DNA-equivalent. (These are known as the Membranabiota, for they have only a cell membrane, no cell wall.)

The Penglaian Period

(Named after Penglai, which was at a similar stage with microscopic anaerobic life, including stromatolite-analogues before colonisation)

From about 3.5 bya to about 3 bya. At the beginning of this period, an offshoot of membranabiota migrated to the ocean surface and developed the ability to photosynthesize. Although their indigo-colored pigment provided plenty of energy, they never evolved to break carbon out of carbon dioxide and release oxygen. Instead, they could only derive carbon by breaking down other organisms, particularly dead ones, or from dissolved carbon compounds in the water. Some in shallow volcanic areas combined photosynthesis with chemotrophy. A closely-related membranabiota group developed which focused on decomposition and absorption, sometimes supplemented by chemotrophy. Meanwhile, (as genetic comparisons indicate) a prokaryotic group developed in this period which preferred more moderate temperatures and spent much of its life blowing around it the high atmosphere, dormant most of the time and absorbing organic material when it could. They increased in population and size as membranabiota spread, and developed cell walls with aerodynamic shapes. Climate changed little; scattered proto-continents spread.

The Euripidian Period

(Named after Euripides Mey, a garden world with similar characteristics)
From 3 billion years to 1.4 billion years ago.

An airborne prokaryote developed its own form of photosynthesis, using a blue-green chemical very similar to chlorophyll. This led to an explosion of aeroflora. Larger forms absorbed other cells and develop nuclei. These became the Murobiota, named for the presence of a cell wall. Oxygen levels slowly climbed. Many organisms went extinct from its toxicity, but membranabiota was able to isolate it, and developed highly successful forms that used oxygen as part of their metabolism. As murobiota converted carbon dioxide into oxygen, temperatures descended, but stayed largely within the realm of wet greenhouse. This allowed murobiotans to descend to the ocean surface. Some formed floating multicellular clusters; too small for neb eyes to see, except en-masse as a faint discoloration.

Membranabiota developed two multicellular kingdoms as well. Their photosynthesizers simply developed into colonies of cells: the Coloniabiota. These often formed mats in the shallows, or grainy blobs which floated in the muck. The decomposers developed their own kingdom, restricted to cooler climates in the southern hemisphere (the pole or midlatitudes depending on axial tilt). Some formed hollow balls, others flatworm shapes or rippling circles. Each cell in the cluster absorbed nutrients directly. These are known as Ediacaroids, for their descendants would come to resemble Earth's Ediacaran life. None of the three kingdoms reached macroscopic size in the Euripidian, nor had they developed hard parts.

Orwell biota in the Tohulian Period
Image from TSSL and Steve Bowers
Orwell biota in the Tohulian Period

The Tohulian Period

(Named for Tohul, a wet greenhouse world)
1.4 to 1.26 billion years ago.

Geographically, land consisted of forming cratons and island arcs, starting to assemble into continents. Temperatures were steamy, but most of the oceans were now hospitable, though multicellular life (apart from coloniabiota) was rare at the equator. Oxygen levels were high enough to support macro aerobic life, but nothing with complex tissues or high metabolisms.

Murobiota developed the most in this period. Because Norton is dimmer than Earth's Sun, Orwell's photosynthesizers had to stay closer to the surface of the sea to access light. Larger clumps lost the ability to float; early on, one group lost the ability to photosynthesize. Transitional forms are unknown, but they eventually developed into the Swimmer subkingdom. The basal form was shaped like a tube, heavily armored on the outside using thick organic tissue derived from their cell walls. They swam using rows of cilia on the outside, like Earth's ctenophores, while internal rows of cilia collected a steady stream of microorganisms and detritus to eat. Common genetic coding indicates that eye spots and chemical sensors were present, but the arrangement is unknown. They reproduced by budding, which could be either sexual or asexual; hermaphroditic, they could release sperm packets when near others of their species, who would receive them at a budding site, while buds could still develop without sperm. Already in this time, there were likely a number of species who used buds not just for reproduction but to form extra appendages, whether tentacles or fins. Swimmers evolved in the northern hemisphere, but some abyssal filter-feeders migrated south and spread from there, though they weren't as successful there.

Murobiota also developed the subkingdom of Floaters. These managed to grow in size while staying near the ocean surface by developing air-filled floats. The most popular body plan was branched, in which each branch ends with a float. Orwell's high tides often washed these far onto the shoreline, but they couldn't survive on land for long, and required water to reproduce. They released reproductive packets similarly to the Swimmers', but the gametes were unspecialized. Others of the same species could receive and fertilize a packet, packets could meet in the open sea and fertilize one another, or an unfertilized packet could eventually develop into a new Floater on its own. The most successful species developed to send their gamete packets within a detached float. As gamete packets spread easily, they quickly achieved worldwide distribution.

One northern-hemisphere branched Floater subgroup repurposed some of the floats as specialized organs. They retreated deeper into the sea and lost photosynthesis again. They kept the branching structure, with organ-bags at the end, often for digestive purposes, but sometimes containing chemical bacteria, and some developed into sticky holdfasts. The branches could now serve as legs, feelers, and grabbing mouths. Most took up scavenging and detrivorous lifestyles. These are called Branchers.

A few other minor multicellular Murobiota existed as scum, wisps, and floating mats, but were never important components of ecosystems.

Coloniabiota, comfortable with torrid climates, kept a world-wide distribution throughout the Tohulian. Faced with competition from Floaters, one subgroup developed an additional reddish pigment for photosynthesis, which usually gave them a purplish or maroon color when combined with their indigo-colored chemical. These were adapted to deeper zones, where red light didn't penetrate anyway, and they were able to absorb carbon from life above them. Colonial mats spread, indigo ones covering the shallow ocean floor, purple ones the deep floor.

Ediacaroids flourished in the southern hemisphere, undisturbed by Swimmers and Branchers. When they grew larger, they continued to absorb their food directly through the skin, which by necessity stayed thin. In order to achieve a larger size they formed pleated-looking and quilted-looking forms, bunched together into circle-shapes, ellipse-shapes, feather-shapes, fan-shapes, clam-shapes and the like. Some were sessile, attached to the sea bottom with holdfasts or simply sitting in place; others ripple-swam, inched or oozed along. Most Ediacaroids were decomposers. Their major subkingdoms were Soft Ediacaroids and Armored Ediacaroids. The latter developed heavy mineral shells around their outer layer. Water and nutrients would enter through an opening and pool around inside for the cells to absorb and pass along to their neighbors. Some Armored Ediacaroids had many holes; in addition to letting in water, some of these holes provided room for feathery appendages which served as gills and also to catch organic material which they could then pass inside. Some had, instead or in addition, tentacles which served to grab decaying organisms or propel the organism around.

The Panthalassic Period

1.26 to 1.14 billion years ago
Named after Panthalassa, a water world

The Panthalassic began with massive tectonic upheaval, as a series of low-lying continental material coalesced in the northern hemisphere and intense volcanism set in, creating a highly fertile ring of shallow sea. Temperatures dropped sharply in the latter half, with the first ice forming at the period's end. As this was underway, an arc of southern hemisphere islands drifted north across the equator, combining with the low temperatures to produce significant exchanges of life.

The Northern Swimmer Radiation defined the nature of life in this period. The vast shallow sea offered a plethora of niches for the Swimmers, though many of their new forms would prove evolutionary dead ends.

One of the most common alterations was to grow limbs sticking out of the side of the body. Most common were two subsidiary limbs, but some had more, arranged in a ring around the main tube. Formed by budding, these were separate organisms sharing circulation and digestion with the body. Usually they'd hold them to the front, serving as additional grabbing mouths. These were the Multacorpora.

The first predators developed, too: Headfangs. Similar to the original body plan, their armor thickened and extended into fang-like spikes around the front end. Abandoning their cilia rows, they increased maneuverability by jetting water out the back. To maintain their active lifestyle, they grew frilly gills where the cilia rows once were. They attacked by ramming into their prey.

Among their prey, the Chushou grew tentacles out of their cilia rows, useful for foraging between the Floaters and bottom-dwellers. They now moved with an up-and-down paddling motion.

Probably the Flimsies originated at this time, though they weren't fossilized. These were Swimmers whose rigid armor softened. They became light and soft creatures that resembled jellyfish made of seaweed.

Another Swimmer offshoot, the Spongiapublicans, rooted to the ground, closely resembling Earth's sponges. They were unable to compete with Branchers until they developed communal polyp-budding. These formed massive colonies of reefs; once a colony was large enough, new polyps would take up a free-swimming existence and found a new colony elsewhere.

Meanwhile, the Reterami, bottom-dwelling Branchers, rose from the ocean floor. One set of branches became a filter-feeding net; another became a series of propulsive fins, while others stayed close to the body, able to unfold to crawl along the surface when needed. Some of these further changed to latch onto larger organisms as parasites.

As the northern and southern hemisphere came under increased contact, these Swimmers rushed into the south and displaced many of the native forms. Life homogenized.

The biggest shift came when Headfangs reached the equator's fields of Coloniabiota mats. Abandoning predation, some Headfangs repurposed their spikes as grazing rakes. Already tube-shaped, some became long and wormlike and grew digging equipment at their fronts. Other burrowers developed from the basal stock, simpler in form but just as adept. A group of armored ellipse-shaped Ediacaroids followed behind, first using the burrows as convenient places to hide and feast on organic waste, then developing their own ability to root through the murk using protrusions in their armor.

The onset of grazers and burrowers triggered a mass extinction among the Coloniabiota, who had few defenses. No longer could they form extensive mats and mists, restricted to short-lived rapid-growing patches and to marginal zones. Many adapted to disperse into individual cells or clumps when faced with threats, only gathering into larger structures during limited opportunities. Ediacaroids took the mantle of decomposition from Coloniabiota, and as a result developed a number of slow-moving and sessile forms.

The Panthalassic also featured a number of large mysterious coiled fossils, which were probably the shell of some sort of oversized Ediacaroid, but have yet to be convincingly linked. The more excitable scholars like to consider them traces of a visiting spacefaring civilization, but without other evidence, this is unlikely at best. They would not survive past the Darwinian Period.

The Darwinian Period

1.14 to 1 billion years ago
Named after Darwin, a world resembling Earth in the Cambrian Period

Temperatures warmed again during the Darwinian; no permanent ice existed during this age. This may owe to favorable geography. There were two continents in northern midlatitudes, which gradually drifted apart; the largest by continental shelf was mostly flooded. A smaller continent accreted just south of the equator.

Orwell's Darwinian Explosion rivalled Earth's Cambrian explosion. Many more forms existed than described below. Never again would so many body plans coexist so prominently.

The Multacorpora proved the most successful free-swimming group. The use of budding for growth and structure rather than mere reproduction enabled a variety of body plans that sported specialized limbs and protrusions. These always had their own internal organs, though linked with the main body, and could regrow if lost. As nervous systems developed, the separate sections would be only loosely coordinated.

One new plan, Petaloforma, consisted of a main body which branched like petals at either end; both directions could serve as front. The petal-bodies could close for streamlining, open to grasp food, or could serve as rippling fins. They were coordinated enough to move together, but would feed separately. These grew to be Orwell's largest creatures yet. Cilia rows still existed as an alternative means of swimming, many of which had developed gill-grooves. Smaller reproductive buds often grew around the outside where they served as protective armor before detaching; these thickened near vulnerable areas like cilia and gills. Other reproductive buds grew inside the digestive tube, protecting internal organs from injury and parasites.

In one Petaloforma group, Skeletoforma, external buds spread across the outside and inside body like puffy scales, while the main body itself became heavier, forming a thick reinforced tube; effectively a spinal column where one of the digestive tracts lay inside. Three former petal-bodies grew backward over the spine to create a more flexible body outside, holding the main organ systems, each with a heart, a brain, an oxygenated gill patch, eyes, a vibration sense, and a series of digestive sacs and glands. On the other end, three petal-bodies remained as fins. All six of these had the potential to grow back if eaten or injured, as well as to develop into a new organism if separated; note that, due to sexual reproduction, each of the six were genetically children of the spine, not identical. Some continued to grow smaller buds on the outside, or to grow additional layers of petal-bodies.

Some Multacorpora, Quadruforma, developed in an entirely different direction. These originally had a main body with four subsidiaries. Now they took on a bottom-walking lifestyle, where the subsidiary bodies became legs, feelers, and diggers, walking around and rooting through the silt, the main body atrophied, serving mainly to coordinate them. These were also notable for developing compound eyes.

The other major Multacorpora spinoff, Segmentaforma, grew their bodies not as appendages but in long chains of segments. Long and thin, some darted around like eels, while others burrowed like earthworms.

The Headfangs grew stunningly large, but changed little, and barely diversified, though some became more bilateral and some more radial.

The Chushou developed three new offshoots. In the Fin Chushou, tentacles in the back broadened and became muscular, thus becoming fins. Shell Chushou further developed from there, growing a shell that encased the back end, with only a hole for excretion. This support allowed them to achieve greater sizes. Flat Chushou developed from the basal stock, abandoning the tube shape and developing broad wings so they could soar through the sea like tentacled rays. All Chushou grew their reproductive buds in internal pouches to prevent disruption of their streamlining.

Spongiapublicans entrenched themselves as dominant reef-builders. While some changed little, others developed spines that ringed their main body, serving both as defense and a support structure, allowing individual polyps to grow in size. Many of the largest went on to develop pumping muscle tissue. Their digestive system twisted into a U-shape, they would suck water in one end, extract nutrients through their hair-like internal coating and expel it from the other end. Many of the largest polyps would have a colony of smaller polyps growing inside them, often their own offspring, who would aid in nutrient extraction, exchanging it with their host. Some extended to beaches, where they sealed themselves up during low tide.

Most Reterami remained filter-feeders, growing now to immense sizes. Shaped like tangles of roots, they had little internal structure, merely a vascular system that circulated nutrients from their filter nets. Some lost all vestiges of a nervous system, losing their fins and becoming giant free-floating masses, absorbing whatever got caught inside. A few stayed small and bristly.

Bottom-walking Branchers changed little, and were fairly marginal at this time. They had a general tendency to expand their central body and sometimes sub-branches to accommodate ganglia and blood pumps. One more successful group started producing netting in specialized organ-bags, which they would spread among Spongiapublicans and use to trap prey.

Most Armored Ediacaroids remained on the seafloor. Sessile forms developed a variety of shell shapes and interlocking growth patterns. They may have been under some competition with each other for space. Many show signs of divergent growth in injured areas. Some grew on reefs or stones like barnacles. Burrowing varieties faced little competition, as they focused on consuming waste. These all had low metabolisms for their body size, since the living part of the organism would be only a tiny fleshy coating on the inside. One burrowing organism, however, transitioned to carnivorism, waiting in a hole from which they'd dart out tentacles to snare small passersby.

Soft Ediacaroids were likely in decline, but they fossilize so poorly that it's difficult to be certain. The tropical southern shallow seas feature patterned imprint fossils which likely indicate pleated bodies covered in fractal fuzz that rippled across the seabed, though their ecological role is unknown, and they would leave no descendants. Meanwhile, genetic studies suggest that quilted forms developed bilateral symmetry and began using their internal sacs as storage reserves, allowing them to exist in marginal areas far from predators (to which they were highly vulnerable). These reserves also enabled skin that was more than a few cells thick; capillary systems delivered nutrients from the reserves across the body rather than direct absorption. They also developed sensory hairs to detect vibrations and chemicals (but not eyes, for they tended to live away from sunlit zones). This may also have been the period of origin of Butterfly Ediacaroids, where two separate ovals joined in the middle, where central muscle tissue would contract and allow rapid swimming when they sensed movement nearby. A few of these secreted support tissue in the center similar to cartilage.

Outside the Ocean

Floaters led the first push from the sea. What were once mere reproductive floats remained as mature Balloons; little more than a photosynthetic membrane around a bunch of oxygen, bobbing on the ocean surface and often caught up by the wind. The tide would frequently leave these stranded high ashore, where they would continue to photosynthesize, rehydrating when the tide returned, rain came, or the wind returned them to standing water. Some took to storing water instead of air when needed. Other Balloons grew gliding wings so as to spread far through the atmosphere and disperse across the world. Those that landed in dry climates would die, but far inland areas were rare.

Other Floaters retained their branching structure, but developed waxy surfaces resistant to desiccation, forming jumbled messes just past the tide.

Musci, wispy Murobiota, also colonized moist areas, similar to moss.

Two types of Armored Ediacaroids colonized the land. One was a sessile form with a tall shell that extended outward like a vase (from which they derive the name Huaping). Stranded by low tide, the water would remain, even replenish with rain, and the living cells within could feed off organic material trapped during the previous high tide. The other was a long mobile form with a membrane at the opening of the shell which would close the shell when it was dry.

The first major amphibious fauna came from bottom-dwelling Branchers. In these, some organ-bags became sacs of water. They could continue to extract oxygen from these and therefore remain on land indefinitely; their heavy cell walls put them at little risk of desiccation. On land they could eat stranded Floaters and Balloons and graze on Musci. If they took water from Huapings and released their reproductive packets within them, they never needed to return to the ocean. Huapings benefited too, feeding off of the Amphibious Branchers' dead cells, unsuccessful reproductive packets, parasites, and feces. It was not, however, possible for Huapings to grow past the tidal zone, for they needed to absorb silicates from the water to grow their shells.

Gliding fauna also emerged to take advantage of gliding Balloons or escape predators. The first developed from Flimsies who caught the air like a parachute. Some Flat Chushou developed the ability to paddle so vigorously that they leapt from the water and caught the wind in their wings.
Orwell before colonisation
Image from Steve Bowers
Orwell as it appeared when the first explorers arrived, before the Circumference orbital ring was constructed
 
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Development Notes
Text by TSSL
Initially published on 25 November 2014.

 
 
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