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This snip here was written by the wonderful Masterweaver! I have done no edits whatsoever, though if they edit it in the future I will also edit this to match.
APOCRYPHA: Earth Species, a Primer – by Masterweaver
Earth Species, a Primer
As Put Forth By Padmin Vilmis
Draft 12
Earth has had numerous unusual influences on its geography, technology, and biology over the course of its history. Space-time dimensional anomalies, confirmed reports of ancient and powerful eldritch beings, and multiple alien colonizations have led to a planet with a very unique planet. The following is an attempt to explain the modern population as well as the civilizations that formed it.
Precursors: Ancients, Babylonians, and Zeti
By far the most influential of the precursor races would be the species referred to as the Ancients. Arriving in a colonization fleet after the destruction of their own planet by an outside force, the Ancients prioritized islands and isolated regions for colonization, with their primary homestead being on the Starfall Islands. This, in combination with the artifacts they brought known as the 'Chaos Emeralds', resulted in the islands having a large amount of environmental and technological differences from the main continents. Modern scholars believe the focus on the islands was two-fold: One, to avoid disturbing the already existing but primitive local sophonts, and two, because the ancients' unique biology was best suited for island life. However, the entity that destroyed their planet followed the ancients to Earth, prompting them to utilize their technology to contain it within a machine in their capital city, and further evacuate to a backup colony on Angel Island. Due to unknown factors, the Ancients' genetic code mutated, transforming them into the species known as Chao-worth their own discussion, see below-and the closest thing to Ancient Culture to survive is their mechs, the VI assistants known as Koco, and the datafiles on their ancient computers.
While the Precursors had a large role in shaping the geology and biology of Earth, the Babylonians would have a large role in shaping its culture. Their vessel was designed to splinter off component parts in case of complete malfunction, but they were not prepared for all of their drives to glitch out at the same time and were forced to make a crash-landing on the planet while they launched their drive components into orbit. They strove to reconstruct their ship, raiding the primitive civilizations around them for their own survival and passing off their technology as magic, but over time they were forced to interbreed with a certain subset of Islanders-see Islanders, below-and eventually, as they never developed the numbers needed to become a nation of their own, their civilization simply fell apart and dissipated into the surrounding culture. I have had the fortune to meet one of the few confirmed descendants of the Babylonians, who has tentatively admitted an interest in locating the ancient homeworld, but due to the current planetary situation does not feel the need to persue such an endeavor.
The final 'Precursor' race has actually had minimal impact on the planet itself, but a significant impact on the artificial satellite known as 'The Lost Hex'. They are also the only precursors to exist as an extant species in the modern era, albeit geographically limited to a specific local. The Zeti are characterized by their highly precise magnekinesis, allowing them to take control of unprotected electronic systems, as well as their long age and extreme durability. Ancient cultures would regard Zeti raids as demonic in origin, something the Zeti themselves willingly encouraged in a sort of warrior culture. That said, the exact relationship of the Zeti to the Lost Hex is unknown-they live there, but it's unclear if they built it, evolved naturally, or were created by whoever initially created the Lost Hex. They have been notably unwilling to engage with other cultures, outside of directed hostilities, but this does not make them stupid or foolish by any means.
Immigrants: Chao, Wisps, and by technicality the Black Arms
The Chao are the mutated descendants of the Ancients, perhaps affected by the very systems that created the Islanders. Chao are not fully sapient, having the intellectual capability of a pre-speech child, and generally gather in small clans or are raised as pets by friendly Islanders. Chao are capable of hovering flight, and their physiology is such that they can mutate and warp in response to certain outside stimuli. One Chao in particular has mutated enough to resemble an Ancient, but acts in a manner similar to the rare Turian that was raised by animals-feral, untrusting, and unable to communicate. It's a sad fate for a once-great race, though certain members of Earth's government are looking into reversing the mutation in a small population-a process that is stymied by both biological and political considerations.
The Wisps are a hive of energy beings, native to a small planetoid that was towed into orbit of Earth by a local madman terrorist. While he initially sought to exploit their power for his own reasons, his plans were foiled, leaving the planetoid in orbit around Earth. The Wisps have since begun integrating into Earth society, offering their powers in trade for various goods and services. An entire industry has cropped up around the development of devices to channel and utilize these powers in an ethical manner. Wisps can also temporarily merge with Islanders-somehow-providing them unique abilities.
The third immigrant 'race' is represented only by one member, a genetically engineered hybrid of an Islander and the Black Arms. The rest of the species could be characterized as an invading, fascist hive mind, and almost took over and destroyed Earth until the hybrid himself destroyed them. The existence of the Black Arms is not a secret, and the hybrid doesn't bother hiding it if asked, but the general public only knows that they were an invading race that was fought off.
Natives: Humans, Islanders, and the odd AI
Humans are asarioid mammals with sexual dimorphism, though their proportions are significantly different from the Asari and, frankly, from each other. They were the original inhabitents of Earth, evolving and spreading across the various continents in a fairly natural manner, and generally remain on said continents (though individuals do make their homes on various islands). In terms of technology and society, they are quite advanced, even having a degree of spacefaring capability-though, admittedly, there is a conflict of interests in that the most technologically capable human faction is the Eggman Empire, the mostly automated forces of the same madman terrorist that towed a planet into orbit. The Guardian Unit of Nations is, in theory, a cross-national military force that can protect Earth's interests, but in practice they are bogged down by bureaucracy and practicality. That said, as individuals humans tend to be quite capable and empathetic, perhaps even to their detriment.
Islanders... are complicated. The current prevailing theory is that the Ancients somehow (whether purposefully or accidentally) triggered a controlled evolution of the local fauna on their islands, resulting in the numerous colorful species that developed on Earth's many islands. This means that Islanders are not one singular species, but a multitude of individual races that have somehow converged into a similar bodyplan. Individuals may refer to themselves by species-Sonic the Hedgehog, for instance-or adapt a more human naming convention; 'Amy Rose' spent most of her life on a continent surrounded by humans. Islanders also have a tendency to develop abilities neither seen in their source species or explainable by current biological understanding, mutations that manifest as a sort of superpower. Their culture tends to be more in tune with nature and the various left-behind technology of the precursors.
And then there are the AIs. Most AIs are developed by the Eggman Empire and range from animal intelligence to full on sophancy, but are hardcoded to be loyal to their creator. As said creator is a terrorist and a despot, any AI that rebels is generally treated as an expatriate of a fascist group and granted full citizenship by the locals, complete with removal of their restrictions. This, thankfully, is a very small number, but the treatment of synthetic life is a very, VERY complicated subject on Earth, even with the prejudice against them.