The Common Ancestor Theory

Common ancestor theory is the study of the genetic similarities and connections between different genesis groups. Its base hypothesis states that a humanoid species in the Milky Way Galaxy, extant three to four billion years ago, seeded a large number of habitable and potentially habitable planets with genetic material and allowed them to flourish or perish either by their own doing or by chance accidents, such as the many extinction level events that occurred on Earth over its long history. 
The charted sectors of the galaxy contain seven known naturally occurring extant sapient alien species with the capacity for interstellar flight either through their own means or by way of allies. In addition, at least three more are theorized to exist or have existed in the past through ancient legends of the neyanta and authiik, at least another half dozen known to exist by way of signals coming from closer to the galactic core, two created through genetic manipulation by other species, and another two whose origins are up for debate or hard to test. 
The extent of the domain of these aliens is not known. It may have spanned the entirety of the Milky Way galaxy and many of its nearest neighbors, or it may have been restricted to areas near the Orion arm of the galaxy. What is known for sure is that there are many obvious parallels in sapient life, far too many for it to have been natural convergent evolution. 
== Summary ==
Approximately 3.5 billion years ago, a humanoid species in, but not necessarily native to, the Milky Way Galaxy placed their genetic information on a number of worlds in the galaxy. Many of these worlds gave rise to a number of descendant sapient species, including but potentially not limited to the bomure, neyanta, garrida, and early humanity. Either the authiik or exai species is known to be the fifth descendant species of the original humanoids, but it is likely that another sapient species, extant approximately 1.8 million years ago, took one and created the other through extensive genetic modification. 
In approximately 25000 BCE, the authiik made modifications to early humans, creating modern humans for use as soldiers in a conflict against the neyanta. The humans began rebelling against them just as the neyanta began invading, prompting them to take a copy of the human genome with a number of edits to the planet now called Yaart in an effort to allow humans another chance to survive the war. This resulted in the creation of the yemun species. 
Millennia later, in the early days of interstellar colonization by humans, they made a number of edits to their own DNA to allow their survival on Demet. This resulted in the ald, une, and prifeli subspecies of Demetian humans. 
== Known Related Species ==
=== Authiik and Exai ===
The oldest known genetic schism between extant species is that between the authiik and the exai. They are native to systems with similar stars, evolved on home worlds with similar surface gravity, and have extremely similar statures, skeletons, teeth, facial features, redundant organs, and dietary requirements. Evidence of genetic editing is present in both authiik and exai DNA, and while the authiik are known to have been extensively tailored, the exai being so heavily tailored is not well explained. The differences present, such as that of their blood composition (authiik blood utilizes hemocyanin while exai blood uses hemoglobin) and reproductive anatomy (authiik use a humanlike arrangement with three separate orifices while the exai have a cloaca and internal layout more similar to the Earth platypus) suggests that the tailoring was extensive, and served to suit their home environment and more closely match other organisms native to their new home world. 
There are two hypotheses that are entertained in relation to this situation The first is that one or the other is a genetic split propagated by another sapient species over 1.8 million years ago. The second is that they are the only surviving populations of said species, who made the changes to themselves and regressed to the stone age due to some great catastrophe. 
As the authiik home world of Udyana was sterilized by the ancient neyanta empire over 27000 years ago, killing all native fauna and the vast majority of the flora, there exists no standard of comparison to test whether or not the exai or the authiik are closer to other life on their respective home planets. 
=== Humans and Yemun ===
The most well known pair of species with blatant morphological and genetic similarities are humans and yemun, who are so genetically similar that, with some care taken and modern medical science applied, the two species can produce hybridized offspring. It was only after first contact with the authiik that the history of the yemun species as heavily genetically modified humans was brought to light. 
This split likely occurred just before the second collapse of the authiik civilization, as the neolithic humans were rebelling against them just as the neyanta began taking their territory. It was unknown whether or not the neyanta were aware of the authiik presence in the Sol system, so a copy of the human genome was brought to a world with a similar enough planet to Earth. A number of changes were made to it to allow it to better blend in with its environment. The first of the yemun were incubated and raised by the authiik on their starships until in their mid teens, by Earth standards. They were then released onto the planet with the knowledge they had gained, and allowed to colonize the new world. 
Authiik leaders of today say this was meant to give humans a chance to survive in case the neyanta were aware of Earth's native populations. It had turned out that they were not, though the authiik do not regret their forbearers' decisions. 
=== Human Subspecies ===
==== Demetians ====
In the early days of human interstellar colonization, long before the invention of the GCC systems allowing quick and easy adjustments to human physiology, a human scouting vessel crash landed on the planet now called Demet, nicknamed Demeter by the scouts marooned there. Its low oxygen atmosphere posed problems for the humans of the day, so a backup plan was put into effect where a new human subspecies would be cloned along with some changes to their genome taken from local fauna. 
The three varieties, Homo sapiens navitas, Homo sapiens unus, and Homo sapiens faeles, all were created under various circumstances, some less savory than others. The vast majority of their genetics are human, but they share some external traits with native primates, including a diminutive snout and various shapes of pointed ears, or feline ears in the case of H. s. faeles, and internal traits including roughly 35% more surface area on the inner surface of the lungs to allow greater oxygen absorption. 
==== Apsics ====
The apsic variety of human was formed because of the cold, dim, and low-gravity environment of the first two colonies that were founded by that group of humans, Rece and Asphodel, led to an increase in height, a decrease in the coloration of the skin and hair, and an improvement to light sensitivity in the eyes. 
=== Other Species ===
While the links between the above seven species are mostly known or confirmed, the relationships between other species are not. The species listed below have little in common with the other species named before or after them aside from their general form as humanoids and likely relation to the original humanoid species. 
==== Bomure ====
The bomure, for instance, are large pseudo-reptilian humanoids. They are extremely territorial and aggressive, and place very little trust in alien life. They have five digits, walk on plantigrade feet, and are warm blooded. Male children are born live while females are laid as soft and leathery eggs, and are native to a star system with a bright white star currently expanding into its red giant phase, making their original binary home worlds uninhabitable.
==== Neyanta ====
The neyanta are cold-blooded catlike humanoids, curious and affectionate around those they like, but neurotic and distant to those unfamiliar or disliked. They have short snouts, tall pointed ears, long and thin tails, walk on four-toed digitigrade paws, are covered in short fur, and give birth to live young two to four at a time. Their original home star is unknown, and their home planet likely no longer exists due to their past history of building stellar-class megastructures. Their current population center is the planet Prrkane which orbits a white star called Prrkan Ni. 
==== Garrida ====
The garrida are a humanoid species that are hard to categorize. They come from a moon called Galla with extremely low surface gravity, only 0.12 gees, and have a single sex using an absurdly simple reproductive system that more resembles spores than egg and sperm cells. They have pale and slightly translucent skin and thin, bony bodies that move gracefully and fluidly in the low gravity of their home world. 
Their most notable trait is their ability to speak with two voices. This is due to each of their lungs having its own larynx and having very precise control of their diaphragm, allowing them to not only chose the pitch of each voice, but also the volume. This makes their spoken languages extremely complex, and gives them qualities that have led humans and other species with similar myths to call them "ghostlike". 
== Unrelated Species ==
While there are five species known to have direct parentage in the common humanoid ancestor species, and another five species made using them as a base, there are another three extant species known not to be related. 
=== Hi-Eukaryota Gelatina ===
Hi-Eukaryota Gelatina, or "hians", are a gelatinous species native to Hi, a jungle moon of Icari in the Lambda system. They have little in common with any life known anywhere else in the galaxy, instead only having analogous cell types in hemogastric cells, nerve cells, and musculoskeletal cells. The form they take when interacting with other species is merely for convenience, as they have no fixed structure and are able to rearrange their bodies at will, and reproduce through self-bisection. 
=== Elania ===
The elania are large bipedal mammals native to the planet Altus that walk on digitigrate feet, featuring thick fur in a similar coloration to Earth northwestern wolves, four digits per extremity, long snouts, floppy ears that droop as low as their mid back, and pointed teeth that betray their carnivorous nature. While there are obvious parallels to Earth species, following genetic testing, there was no direct similarity between their DNA and that of the species that was thought most likely to be related to them, the neyanta, or any other known species. Thus they are analogous rather than homologous, evolving the same forms due to having similar requirements during their evolution.
=== Viskovi ===
While named viskovi by the humans that cataloged their existence, their true name would be difficult to put in writing due to their languages being composed mostly of clicks and whistles of various pitches. The viskovi are avian in nature, averaging 120 - 130 cm in height, featuring large beaks and hollow bones that would be well suited for flight if they had not lost the ability in exchange for the three fingered hands that now reside at the ends of their arms. Their bodies are mostly covered in rough skin and reticulae, similar to those found on the feet of Earth birds, with thin black down and long feathers surviving in many of the same places where humans have retained their body hair. 
They are the most recent native alien species to be discovered by humans, residing on a Mars-sized planet orbiting a Sol-like white star and currently occupying the Steam Age of the Modern Group. Following testing, they were found to have no genetic information in common with the majority of life in the galaxy.
== Legendary Species ==
There are at least four species believed to either exist or have once existed due to their presence in the records of various alien species. 
=== Brak ===
The brak were an arthropod species operating under a hive mind native to a star system closer to the core of the galaxy. While their home habitat is not known, they are believed to be capable of surviving anywhere oxygen is present in the atmosphere. They have not been seen since around 18000 BCE, when the neyanta entered into a war with them that resulted in the destruction of a vast majority of their existing megastructures and caused the fall of their empire. Their weapon of choice is asteroids fitted with subspace drives. This causes them to strike their targets at many thousands of times the speed of light and cause massive destruction. The neyanta posit that if they had not entered their territory, they likely would not have been forced to fight, at least not until the brak decided to expand into neyanta space.
As their status is unknown, it is impossible to test whether or not they are related to the C.H.A., though the likelihood is low. The reason for their vanishing may be due to a war between queens that drove them into extinction, or they may have found more attractive colony targets on the opposite side of the galactic core, causing queens closer to the Orion Arm to retreat to further stars. 
=== Life in the Large Magellanic Cloud ===
==== "Shatikteh" ====
According to the record aboard vessels belonging to the Second Extragalactic Expedition, there were two species in the Large Magellanic Cloud that were at war when they arrived around 16000 BCE. One never made contact with the Authiik, while the other was recorded under the name "shatikteh". They were an arthropod race that, unlike the brak, did not operating under a full hive mind, though they did share an intuition as to what the other members of their species was planning, allowing very effective coordination between groups. It is assumed that they were an egg-laying species, though this cannot be proven. 
The authiik engaged in limited trade with the shatikteh before founding a colony called Roxash. The war in the small galaxy spread to the colony, and the authiik were forced out, leaving the colony to the shatikteh before returning to The Milky Way. The result of this war is not known. 
== Old ==
The Common ancestor theory is the theory that says all sapient life that is currently known is descended from a race that goes back eons. This theory exploded in popularity after the Yemun species were found on the planet Yaart that had a 99 percent DNA match to Humans, with only some appearance traits from the simple native life such as skin tones and fur colors. 
The other two known races at the time found it most peculiar as well, and started passive assistance to the human cause to find evidence of such ancestral lines. This evidence was near solidified when first contact with the Authiik was made and they shared their history with humanity, sad to see the state of their former friends and enemies, the Bomure and Neyanta. 
== Tree ==
The table below shows the species with known links in reverse order of their estimated age.
Species Name 	Basic Info 	Approximate Age 	Generation
Demetian 	3 Varieties, wild variety between them. 	~2K Earth Years 	Great Grandchild to LCA
Human/Yemun 	Baseline humans, Yemuns have blue skin and bright colored hair.	~200k Earth Years (55k since Intervention)	Grandchild to LCA
Bomure 	A pink lizardlike race. 	~550k Earth Years 	Child to LCA
Authiika(Archaeo Sapiens)	The editor of the Human and Yemun species from their own DNA. 	~530k Earth Years 	Child to LCA
Neyanta 	A feline species. 	~560k Earth Years 	Child to LCA
LCA 	The last common ancestor between the known races. 	~1m Earth Years 	LCA
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