Earth After The Colonists: Overview.

First Contact was expected to be many different things by many peoples. To the most optimistic people, it was expected to be a peaceful meeting between the human race and technologically advanced aliens, who would share their technology with all of humanity and advance us beyond the stars. To the anxious, pessimistic and paranoid among us, it was expected to be a disaster that would spell the end of humanity. They might kill us all, enslave us, or take our resources. To online fetish communities, the aliens could use us as hosts to lay eggs inside us, anally probe us, or milk our semen for food or reproduction (somehow). The most reasonable people thought that aliens would ignore us, or deliberately not notify us about their presence in fear of hostility. So when an unknown spaceship was found coming towards Earth in March 2079, it raised many questions around the world, much discussion, anticipation, and fear.

It would turn out that the fear was well-founded, but not just for humans.

When the spacecraft landed in the Pacific Ocean in December 2086 and was soon washed up on the coast of California, it was approached cautiously by a massive team of scientists and military soldiers. The spacecraft of around 15 kilometers in length was opened slowly but surely over the course of an hour, surrounded by heavy weaponry. As soon as it was fully opened, the inhabitants started crawling out from inside, like maggots and flies crawling from a corpse. Or more accurately, a horde of African midge larvae crawling out of cryptobiosis. For this spaceship was not like a proud explorer's caravel in the 15-1700s looking for new worlds to explore, nor was it like a trawler looking to fish resources from the ocean. It was the last hope for a dying species from a world which had long since been devastated and made uninhabitable by a collision with a rogue planet. This species needed a new home, and it was not going to let another sapient race get in the way, for better or for worse.

The alien race in question would become known as the Colonists, named after their motivation for coming to Earth. They were eusocial, whip scorpion-like creatures, though in a sense inverse to that of most eusocial creatures on Earth, in which the colonies were lead by two males, a King and a Viceking, the former of which acted as a reproductive leader and the latter of which acted as a vice in case the King was killed, and would develop into a true King if such a thing happened, growing an oddly mammalian-like penis in the process. The main caste used in battle were the male Soldiers, which were about the size of a polar bear and resembled a gigantic cross between a whip scorpion and an earwig, having two pincers on a spiky tail to kill combatants. The Worker caste resembled whip scorpions and were the size of smaller brown bears, with four smaller pincers for manipulating and grasping objects and only a scorpion-like tail with venom for defense. The female Drone caste was the result of a Worker or Soldier without a third sex chromosome, was the same size as a Worker but with larger pincers, and a mammal-like cloaca or vaginal cavity where a tail would be in males. Soldier castes had a penis but no gametes; the penis' purpose seemed to be to dominate other Soldiers in half-playful, homosexual 'fights' in which their strength could be tested. The winner was the one who managed to insert his penis into the other Soldier's equivalent of an anus. This made them comparable to Spartans, known for violence in battle as well as homosexual intercourse. Kings and Vicekings lived for up to 80 years, Soldiers and Workers lived for 40-50 years and Drones lived for 55 years maximum. They all had a basic endoskeleton as well as an exoskeleton which grew with their bodies, being made of a substance similar to chitin but more functionally similar to collagen, and varied from black to light gray in color. The only native foods found on the ship were several strains of fungi-like organisms, known as Funcrop, which were filled with protein and carbohydrates similar to those found on Earth. Like Earth lifeforms, both Colonists and Funcrop were fundamentally carbon-based. And unlike most eusocial creatures, the castes had some free will, though were still heavily influenced by the King's orders. Think of denominations within a religion.

What followed after First Contact was immediate disgust on the human's side, and they began shooting at the Colonist Soldiers, blowing some to pieces. What could have been a peaceful contact turned into a bloodbath simply because humans thought insects were disgusting. They were at first thought to be relatively non-advanced, but this was disproved when the Colonists started using their technological weaponry. This consisted of back-mounted cannons which could variously shoot explosive projectiles, fire, or solar beams thousands of degrees in heat, as well as carbon-based armor similar to graphene. Colonists began crawling out and soon unleashed another deadly technology: The Apocalypse Bomb. This hydrogen bomb, similar to the original version of the Tsar Bomba in power (100 megatons), shot out into the atmosphere and landed in the heart of Yellowstone National Park, digging several tens of meters into the ground before exploding. This triggered earthquakes, and before long, the eruption of the Yellowstone Caldera. The sheer amount of ash shot into the sky meant that the Colonists could no longer use solar weapons, but they did cripple the United States military forces. And strangely enough, the current King of the Colonists at the time thought this could be the perfect time for a truce. Perhaps, they thought, they had gone too far. They were like insects in appearance, but they had more advanced emotions, not as advanced as a human but comparable to a higher primate such as a gorilla. They felt some empathy, and they wanted to show it. When other militaries of the world showed up to get rid of the Colonists, the Soldiers simply shielded themselves and showed no offensive hostility. They began communicating in cicada-like sounds, and although it would seem silly to humans (the Colonists just condemned millions if not billions to starvation for crying out loud!), they genuinely wanted a truce. Some countries withdrew troops from the Colonist epicenter, and sent ambassadors instead. The King of the Colonists withdrew his Soldiers and sent Workers instead, retrieving Ashsoak Bombs from the ship in the hope that they would be launched and could clear up the sky to prevent a disaster. The next few days looked hopeful.

Until the Viceking of the Colonists, hungry for power and thinking the King was cowardly, attacked the King unexpectedly. Ripping out the King's genitals and essentially disemboweling him, the King died a horrible death. As he became the new King, a few Soldiers, Workers, and Drones managed to resist, but the majority were loyal to their new King, who commanded them to attack the human race. All hope for permanent peace between the species was now lost as several smaller bombs were shot into the atmosphere and were landed in various parts of the world, including several major cities, exploding like radioactive meteorites. Along with the eruption of Yellowstone, this would be the beginning of the end of the world as we knew it. Yellowstone and other hydrogen bombs crippled the nations of the Northern Hemisphere, where most militaristic nations such as the United States, Russia and China were located. Workers and Soldiers helped raze the lands of the Northern Hemisphere, gathering materials from cities and killing human soldiers and civilians alike to build their new colony. Once humanity was gone and the dust was settled (literally), Earth would become their new homeworld. The Southern Hemisphere held out for a few years, with nations such as Australia, Argentina and New Zealand holding out defensively for a while, but as new Soldiers were bred, new weapons build and cities built (resembling giant, metallic termite mounds), they were eventually taken over. The last colony for humanity and the few tens of rebel Colonists was, and still is to this day, Antarctica, located under a small mountain near the coast which had been warmed by climate change. Living off geothermal energy, the food needs of the city of Neoterra are met by a combination of fungus, algae grown under lights and genetically modified yeasts which can produce rudimentary forms of milk, eggs and medicines. Along with other fungi and humans, the colony is inhabited by a scarce few non-human animals, including slightly evolved/modified versions of Belgica antarctica which can live in slightly elevated temperatures, genetically engineered pseudohybrids of the Siberian salamander and various cave salamanders (aquatic and terrestrial forms both exist) and various tardigrades, pseudoscorpions and nematodes typically not accounted for. Slowly expanding below Antarctica's surface, careful not to break the surface to avoid detection by hostile Colonist troops, it represents humanity's last current refuge at a population of about 120,000, and can be likened to the fictional Zion in the Matrix movies, only with less light and more rock and fungal bricks. The ethnic population is mixed race, comprising Caucasian, Polynesian and Asian bloodlines with spots of African and Hispanic in ancestry.

Outside Neoterra, on the surface of the Earth, much has happened in the last ~2,500 years since First Contact. Several Colonist Kings, and therefore several functional “nations” now exist, typically in hostile relationships short of war due to differing ideologies. The vast majority of Colonists believe humans to be entirely extinct, and a treaty has been signed to prevent active searching for new humans after the death of the bloodthirsty King that unleashed the Human-Colonist war. The vast majority of macroscopic Terran lifeforms outside Antarctica have been eradicated either intentionally or accidentally by razing of the land and sea for resources. A group of Colonist environmentalists concerned about Earth life have launched conservation programs to protect some of Earth's biodiversity in some shape or form. This includes the “accelerated evolution” through genetic engineering of an oceanic ecosystem similar to that during the Devonian period. Genetically modified tubeworms with symbiotic photosynthetic bacteria form replacements to extinct coral reefs, while marine yeasts, protozoa and tardigrades form much of the “plankton” and seabed biota. Bony fish appear to have gone completely extinct, but oddly enough, a single species of shark survived long enough to become the basis for a new radiation of fishes. The bonnethead shark (Sphyrna tiburo) was an opportunistic, fast-breeding shark species which dominated the coastlines of the Americas before the reign of the Colonists, having expanded significantly due to recent global warming. A miniaturized strain about the size of a dwarf lanternshark (Etmopterus perryi) was engineered to feed on the surviving shrimp and amphipods, and was released into the ocean, currently having speciated into several distinct forms, some of which are hypercarnivores which feed on smaller crustacean-eating sharks. On land, a scrappy few lichens eke out a living on mountaintops and coasts. The fate of cave-dwelling animals outside Antarctica remains unknown.

Hey r/worldbuilding, hope you enjoyed this! It comes from a concept I had four years ago, where a bunch of alien bugs terrorize the Earth until no vertebrates were left but some genetically modified sharks. I've decided to expand it and allow humans to survive with a few GM creatures living in caves. I may or may not expand it at some point, depends on feedback.

EDIT: Suggestions are also welcome.