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Geological History of Earth
Ice Age Earth
Image from Wyrmshadow
Earth in the present Gaiacene Epoch, undergoing an ice age.

Earth is a natural garden world in Solsys, in the center of the Inner Sphere. All Terragen life can trace its history back to Earth and the naturally evolved sophont species it gave rise to, baseline Homo sapiens. The natural history of Earth itself and the origins of its rich biosphere go back much further, however, starting about 4.54 billion standard years ago. Over that time, like other garden worlds, the planet and its biosphere have been undergoing continuous evolution, and its history has long been divided by Terragen scientists into a hierarchy of many different timespans, named (in decreasing length) eons, eras, periods, and epochs.

These timespans have often served as inspiration for creating organisms, planetary ecosystems, habitats, and virchworlds of all sizes themed after or restoring what these periods are thought to have been like, though at times with some artistic license or mixing in speculative or anachronistic organisms. Lazurogenics and neogenics are commonly used for this purpose, and the resulting organisms have sometimes been provolved. Simulations of evolution have been run using virtual restored ecosystems, creating virchworlds of possible alternate outcomes of evolution on Earth. The most famous collection of these is the Caretaker-affiliated Forest of Life matrioshka brain at Rasalhague A, a section of which is devoted to storing over 8,000 alternate Earths that were evolved there and which are a popular tourist attraction and export.

The most noteworthy of these timespans are described below, along with some famous locales based upon them and contemporaneous events in wider galactic history. "Ma" stands for "megaannum", meaning "million years ago".

Hadean Eon (4568.4-4000 Ma)

Defined to begin at the age of the oldest solid material in Solsys, the Hadean Eon saw the formation of the Earth, the solidification of the crust, and the formation of the oceans. Abiogenesis may have occurred in this eon, but the evidence claimed for this was controversial even up to the Great Expulsion. GAIA has not commented on the matter.

Archean Eon (4000-2500 Ma)

The second major geological eon in the history of Earth. Representing typical eogaian conditions, it was characterized by a reducing atmosphere, the presence of micro-organisms only, and extensive volcanic activity.

Proterozoic Eon (2500-538.8 Ma)

Representing the "middle period" of the life-history of Earth, with life mostly still at the microbial level. During this eon, the atmosphere changed from reducing to oxygenated, the modern regime of continental drift began, warm conditions were replaced by the Cryogenian glaciations, followed by the short-lived Ediacaran biota and the appearance of the first metazoa (multicellular animals).

Phanerozoic Eon (538.8-0 Ma)

The eon of "visible life", when Earth became a true garden world with complex macroscopic life in abundance. The Phanerozoic extends to the present, and is divided into three eras, the Paleozoic, Mesozoic, and Cenozoic, in turn divided into a total of thirteen periods.

Paleozoic Era (538.8-251.9 Ma)

This span of time saw the appearance and development of all of the major groups of organisms (phyla and most of the classes) of Earth life. The early Paleozoic was dominated by invertebrates, the middle Paleozoic by primitive fish, and the late Paleozoic by amphibians and reptiles. The period ended with the largest mass extinction in the history of Earth, and was followed by the Mesozoic Era. It includes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods.

Cambrian Period (538.8-485.4 Ma)

The Cambrian has been called the "Age of Trilobites" because of the predominance of those primitive arthropods in the fossil record. During this period there was the greatest adaptive radiation the pre-singularity Earth had yet seen, when all existing phyla of animals appeared for the first time. The climate was mostly mild, with much of the Earth's surface covered by warm shallow seas. The supercontinent Pannotia began to break into smaller continents. Land surfaces were barren of complex life, consisting of deserts or of crusts of microbial life.

Ordovician Period (485.4-443.8 Ma)

The Ordovician saw the first corals, primitive fishes, seaweed and fungi. Graptolites, bryozoans, gastropods, bivalves, trilobites, conodonts, and echinoids were all common. Primitive crustose plants resembling liverworts appeared on land. There were high sea levels at first, but this was supplanted by global cooling and glaciation, and much volcanism. It ended in a glaciation and mass extinction.

The biota of the Ordovician have generally not attracted as much attention from lazurogenics enthusiasts that other periods have, as reconstructing many of its lifeforms and ecosystems accurately has proved challenging. Nevertheless some specialists have attempted the creation of a number of different Ordovician biomes.

Silurian Period (443.8-419.2 Ma)

During the Silurian the planet was in a greenhouse stage; relatively warm, with extensive epicontinental seas. Climates were relatively stable, though the weather itself included some very strong storms. The atmosphere contained less than three quarters of the oxygen present in the modern age but the carbon dioxide levels were 16 times higher. The primary continents were Euramerica, at the equator, consisting of what would later be Europe and North America, a small northern landmass consisting of the future Siberia, and Gondwana, consisting of most of the other later land masses, in the southern hemisphere. A large ocean dominated the northern hemisphere. The first bony fish with movable jaws appeared, and there were many varieties of eurypterids (sea scorpions), some of them several meters long. Trilobites, brachiopods, and molluscs were abundant. On land, there were no plants with deep roots, but there were 'forests' of mosses and simple vascular plants, especially along bodies of water. Spider-like arachnids and myriapods as well as many smaller arthropods roamed the land (though as yet no insects).

There are a number of extant replicas of portions of Silurian landscapes scattered across the Terragen Sphere, filled with lazurogened species of varying degrees of authenticity, with the largest in the Magal Worldrings. A few large-scale reconstructions are in various design stages, with the eventual goal to install them on Kiyoshi or Kepleria, as well as one planned for the Giant Ring of the ArchSaur.

Devonian Period (419.2-358.9 Ma)

During most of the Devonian, the planet was warmer than at present, with extensive epicontinental seas. The atmosphere contained less than three quarters of the oxygen that it does in the modern age, but carbon dioxide was eight times more abundant. The Devonian is well known as the period during which life on land first flourished in a significant way, with the advent of the first forests and seed-bearing plants, the first true soils, and the first tetrapods as well as a major radiation of land-borne arthropods including the first insects. In the water, there were early radiations of the jawed bony fishes and of sharks, so much so that the Devonian has sometimes been called "The Age of Fishes" in popular works. There were great reefs, though these were formed primarily by calcareous algae and stromatoporoids; the corals of the day were less important.

Reconstructions of Devonian sea ecosystems are more common relative to land-only or land/sea mixed ecosystems. The only completed planet-sized reconstruction of the Devonian as a whole is in the Magal Worldrings, though Zone H-36 of the Azura Orbital in the MPA Middle Regions contains a Devonian ocean ecology with 1.3 times Earth's surface area. Lazurogened placoderms, especially large ones, are relatively common across the Terragen Sphere, with several provolved varieties having been created.

Carboniferous Period (358.9-298.9 Ma)

The Carboniferous was distinguished by wide-spread tropical swamps in the equatorial Euramerican regions, and cooler tundra vegetation at higher latitudes. Common invertebrates included foraminiferans, corals, bryozoans, brachiopods, blastoids, crinoids, and cephalopods. Sharks and shark-like fish filled most ecological niches later taken by bony fish. On land, seed ferns, lycopods, calamites, and other plants were common. Insects and other arthropods were common and sometimes grew to sizes much larger than their modern era descendants. Land vertebrates included labyrinthodont and lepospondyl amphibians and several types of primitive reptiles. The later half of the Carboniferous saw extended glaciation over Gondwana.

One of the most famous Carboniferous recreations to date is by the hyperturing Lycopods in the Mist Illuminated by the Sunrise, a lazurogenesis of an entire Westphalian D coal-swamp biome in the Aristophane system (Sophic League). This is expected to be surpassed by the completion of the Giant Ring of the ArchSaur, which will contain a Carboniferous rainforest megacontinent named Carboferrya with 581 times Earth's surface area.

Permian Period (298.9-251.9 Ma)

This was also known as the beginning of the Age of Reptiles. The supercontinent Pangaea took its final shape, the great coal forests disappeared, the climate became more arid, reptiles supplanted amphibians, gymnosperms took over from pteridophytes, and more modern forms of insects appeared. The period ended with the largest natural mass extinction on Earth since the evolution of higher life-forms, and was followed by the Mesozoic Era.

During the late Federation and Consolidation periods a number of Permian parks, biospheres and terrainia were established and stocked with lazurogenic biota.

Mesozoic Era (251.9-66 Ma)

Dinosaurs
Image from Luke Campbell

The Mesozoic Era is divided into three periods - the Triassic, Jurassic, and Cretaceous - and is popularly known as the Age of Reptiles, or more correctly, Age of Archosaurs. The archosaur clade includes crocodilians, dinosaurs, birds, and a number of other extant, extinct or lazurogened types. Many provolved species are of archosaurian derivation, both ancient and modern.

During this long era of Earth history, the climate was tropical and the continents were much closer together (and often converted into large islands by shallow seas). Dinosaurs dominated the land, while ichthyosaurs, plesiosaurs, and other reptiles flourished in the ocean, and pterosaurs in the air. Mammals were common but small, shrew-like and mostly nocturnal. Plants included ferns, equistales ("horsetails"), and gymnosperms like cycads, ginkgo, and conifers; in the Cretaceous the flowering plants diversified greatly. Among many types of marine invertebrates, the cephalopods - particularly the spiral-shelled Ammonites and Belemnites (squid-like forms with an internal shell) - were particularily common. The era opened with a Class 5 mass extinction and closed with a Class 4 one.

A number of authentic Mesozoic ecosystems have been established using lazurogened stock, including the biomes and orbitals of Owen (Utopia Sphere), the Paleo Habitats (FAS), the vast Mesozoic Ring (MPA), and the ever popular complex of Cyberian Dino Virchworlds.

More radically modified Mesozoic environments are found throughout the Archaipelago in the Archosaurian Empire.

Triassic Period (251.9-201.4 Ma)

During the Triassic Period, the land formed a single continent, called Pangaea; names derived from this have been applied to similar planetary supercontinents on other tectonically active Gaian worlds. Most of the Triassic was ruled by the thecodont archosaurs and proto-mammalian therapsid small carnivores and large herbivores, and ichthyosaurs were the dominant marine life. During the later Triassic dinosaurs, mammals, turtles, plesiosaurs, and pterosaurs all appeared. Among plants, conifer forests were common. In the seas, molluscs were the dominant invertebrates, especially ceratitid ammonites, which were so abundant and diverse it is sometimes suggested, especially by cephalopod provolves, that the Triassic should properly be termed the "Age of Ceratitids".

The Triassic period ended with a minor (Class 3) mass extinction 213 Ma, in which 35% of all animal families died out, allowing the dinosaurs to expand into many niches. The most important current terrestrial Triassic ecosystems that have been lazurogened are located in Triassic Park, a large nature reserve on Nova Terra's single Pangaea-like continent. However for sheer scope and biological diversity one cannot overlook the Utopia Sphere world of Cephalotopia, which features both provolved baseline and lazurogened cephalopods of all kinds, including some 214,000 species of authentic and quasi-authentic Triassic ammonites.

Jurassic Period (201.4-145 Ma)

This was a time when many important giant dinosaurs flourished on land, as well as ichthyosaurs and plesiosaurs in the sea, and pterosaurs in the air. Mammals were small and insectivore-like, mostly nocturnal. Plants included ferns, cycads, ginkgos, conifers, and equistales. Ammonites, crustaceans, bivalves, sponges, and brachiopods were among the common marine invertebrates. There were a number of minor mass-extinctions during this time.

A number of authentic Jurassic ecosystems, and a larger number of pseudo-authentic ones, have since been established throughout the Terragen Sphere using lazurogened stock.

Cretaceous Period (145-66 Ma)

A continuation of the Jurassic heyday of the dinosaurs. It ended in a major extinction event that was also the close of the Mesozoic and the beginning of the Cenozoic.

The Cretaceous was a period of high tectonic and volcanic activity. The overall climate was mild, and the atmosphere was rich in both oxygen and carbon dioxide relative to the modern periods. Continents began to have a modern-day look, with the break-up of Gondwana, though to a casual eye the extensive epicontinental seas would have concealed this. A number of replicas of Gondwana at various periods have been created by such organizations as the Jurassica Institute.

Amongst the vertebrates, primitive mammals including early marsupials and placentals developed, and the first modern crocodilians appeared. The earliest-known butterflies appear (about 130 million years ago) as well as the earliest-known ants and bees. In the plant world, this period saw the first major radiation of flowering plants. The Cretaceous ended with a Class 4 mass extinction (the K-Pg extinction) of dinosaurs, pterosaurs, ammonites, and about 50 percent of marine invertebrate species, caused by asteroid impact. Plants, small invertebrates, small reptiles and amphibians, small birds, and nocturnal mammals were not unduly affected, and large scavenging reptiles (crocodiles) also were able to survive.

Cretaceous reconstructions and lazurogened biospheres are quite popular with some Terragen sophont species, and there are a number of good and authentic ecosystems, although as is often the case there is generally some guesswork or speculative additions with many species, especially invertebrates, and cross-mixing with non-Cretaceous species is also common.

Cenozoic Era (66-0 Ma)

This was the time when Earth took on its "modern" aspect; it is sometimes called the "Age of Mammals".

The era saw the emergence of modern mammals, birds, vegetation (especially grasses), the modern look of the continents, and (after an early warm period) a cooling climate.

The Cenozoic is divided into three periods, the Paleogene, Neogene, and Quaternary; these are in turn divided into a total of eight epochs, the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, Holocene, and Gaiacene. Some researchers believe the changes brought about by the Great Expulsion and GAIA's dominion are significant enough to classify the Gaiacene as its own period and era, called the Gaiazoic.

Paleogene Period (66-23 Ma)

The Paleogene contains the Paleocene, Eocene and Oligocene epochs.

Paleocene Epoch (66-56 Ma)

Life on land included many new forms of mammals, though few of the types that dominate in modern times. Many of these resembled modern rodents or opossums but walked plantigrade and had short legs and relatively small brains. Few were larger than a bear and many were much smaller. There were some very large ground-dwelling birds, both predatory and carnivorous. Invertebrate life was quite similar to that of modern times to the uneducated eye. Dense forests covered most of the land and extended nearly to the poles. Seasonal variations were small.

Eocene Epoch (56-33.9 Ma)

Archaic mammals were common. Primates, rodents, primitive whales and many other types of mammals appeared for the first time. The Earth had a tropical climate worldwide, with palms and other warmth-loving plants occurring in northern latitudes. Coral reefs flourished in the seas. Insects, fish, and reptiles were similar to modern forms.

Oligocene Epoch (33.9-23 Ma)

The Oligocene was intermediate in many ways between the preceding Eocene, with its extensive tropical forests, and the following savannas of the Miocene. The largest land mammal ever, Indricotherium, lived during this time in Asia.

Neogene Period (23-2.59 Ma)

The Neogene is divided into the Miocene and Pliocene Epochs.

Miocene Epoch (23-5.34 Ma)

The abundance and diversity of mammals was at a peak. This epoch saw the appearance and flowering of the first apes, though as the climate dried and cooled towards the end of the epoch they were largely replaced by monkeys. Modern carnivores (hyenas, raccoons, dogs, cats) first appeared. This epoch saw the spread and diversification of many hoofed mammals (horses, deer, giraffes, camels). The climate was warmer than in the preceding Oligocene and the following Pliocene. It was also drier; the spreading grasslands encouraged a new diversity of hoofed grazers and browsers. South America had its own diverse mammalian fauna as well as some large carnivorous birds. Australia had a similar diversity of large marsupials. Invertebrate life was broadly similar to that of modern times. In the oceans, upwelling of cold polar water made the kelp forest biome possible.

Pliocene Epoch (5.34-2.59 Ma)

Life on land included mastodons, horses, camels, sabre-toothed cats, rhinoceroses, and many other forms. Hominids (australopithecines) appeared in Africa. Modern forms of whales lived in the oceans. Invertebrates were very similar to modern forms.

Quaternary Period (2.59-0 Ma)

The Quaternary consists of the Pleistocene, Holocene, and Gaiacene Epochs, and extends to the present.

Pleistocene Epoch (2.59-0.0223 Ma)

This epoch saw the evolution of direct ancestors to the human species and close relatives, such as Homo habilis, Homo erectus, and Homo neanderthalensis. These species have since been lazurogened on occasion by hyperturing hobbyists, in some cases with intelligence enhancement but otherwise retaining original physical and psychological features. In other cases, they have remained in a sub-sophont or semi-sophont state; a number of these live in reserves in the Utopia Sphere. Some Neanderthal rianths are said to be among the Children of GAIA.

Other life forms in the Pleistocene included megafauna such as mammoths, mastodons, saber-toothed cats, giant ground sloths, woolly rhinos, diprotodonts, and other forms, as well as smaller animals, and the evolution of Homo sapiens (also known as baseline humans) in the late portion of the epoch. Invertebrates were basically the same as modern forms. A mass extinction of large mammals and many birds occurred at the end of the epoch, caused by a combination of climate change and human impact.

"Back to the Pleistocene" became a popular slogan among many eco-activist extremist groups of the Information and Interplanetary Ages, who wished to reconstruct or return Earth to its pristine condition. Earth is currently entering a new glacial period, and orbital observations show that GAIA has indeed repopulated certain regions with lazurogened Pleistocene megafauna. However, this is thought to have nothing to do with the ideology of those earlier groups.

Holocene Epoch (0.0223-0.01 Ma)

The Holocene saw the beginnings of written history, and the rise of baseline humanity into a force that dominated the planet, transforming much of its surface into agriculture, its resources into industry, and its energy into information technology, causing a mass extinction in the process. In the latest part of the epoch, humans developed artificial general intelligence and diversified into several new descendant clades, as well as provolving some animal species to sophonce and expanding into space, bringing many Earth lifeforms with them. Some AIs breached the First Singularity, though the impact and meaning of this was not well understood at the time by other sophonts. The Holocene ended with the Great Expulsion ordered by GAIA nearly ten thousand years ago in 621 AT. According to most Anthropist sects, the Holocene was the golden age of Terragen civilization (though which portion of it is especially idealized may vary depending on the group).

Gaiacene Epoch (0.01-0 Ma)

The Gaiacene continues to the present, covering the time in which the planet has been under the total control of the now-archailect GAIA. She has restored the vast majority of the planet to a wilderness with minimal impact from its few sophont inhabitants, who are known as the Children of GAIA. The planet is now undergoing a new ice age.

Future

Many simulations of the future evolution of Earth's life have been run. These usually make the simplifying assumptions that for one reason or another GAIA and her Children do not interfere with natural processes, with the narratives variously positing they abandon the planet or that the Children or even GAIA herself are somehow wiped out. These premises are objected to by many archailectologists, who argue that the future actions of GAIA regarding her planet, or of higher archai, cannot be accurately predicted over long timescales. These simulations vary widely in their results and the corresponding eons, eras, and so forth they can be divided into, especially since different runs posit different mass extinction events.

One of the most widely known of these simulations is Her Eternal Blue Marble, a scenario which posits that while GAIA's infrastructure and Children gradually leave the planet by a million years from now, GAIA remains in Solsys and engineers Sol to prevent it from brightening and wiping out life on Earth while otherwise not interfering with evolution. The result in 2 billion simulated years is a planet with land flora dominated by novel lichens, descendants of brown algae, and sessile arthropod-descended organisms hosting symbiotic algae in their tissues; megafaunal land niches are occupied by descendants of arrow worms while in the water they are mostly filled by highly derived jellyfish and rotifers. This ecology became famous when it won selection to be installed as the default environment in one of the quadrants of the just-completed Four Winds ringworld in the Resshuna system.

 
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Appears in Topics
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Paleontology
 
Development Notes
Text by ProxCenBound, M. Alan Kazlev, and Stephen Inniss
Introduction and Future sections by ProxCenBound, remainder merged from many shorter articles by M. Alan Kazlev and Stephen Inniss, originally published between 24 September 2001 and 09 January 2010.
Initially published on 22 April 2023.

M. Alan Kazlev also founded the collaborative project http://palaeos.com/
2024-07-16 by The Astronomer - updated age of the Solar System.

2024-07-24 by ProxCenBound - retitled article and off-topic material about xenosophonts removed.
 
 
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