Super Mutant

Super mutants or meta-humans are mutated humans, products of the Forced Evolutionary Virus, or F.E.V.. They are much taller and bulkier than humans, have (mostly) green, gray, or yellowish skin, are immune to disease and radiation, and are gifted with superhuman strength and endurance. Although they are completely sterile, constant regeneration of their cells caused by FEV makes them biologically immortal (but not immune to death from injury, of course).

There are two different known sources of super mutants - Mariposa Military Base in the Core Region (West Coast) and Vault 87 in the Capital Wasteland (East Coast). The two populations have separate histories, and there are no known accounts of any interaction between them.

Biology
Average super mutants stand approximately 10.5 feet (3.2 meters) tall (although they typically stand with hunched backs that reduce them to about 8 feet, or 2.4 meters) and weigh around 800 pounds (360 kg), possibly even more. Their skin color is predominately gray with tints of green, although some mutants with other skin colors also exist. Their skin is extremely tough, and their muscle and bone structure are enhanced.

Super mutant cells undergo cellular division at an increased rate. Mitosis occurs at a rate 15% quicker than that of normal humans. Cellular structure is said to be highly similar to normal humans. DNA strands are very complete, with all recessive genes for ailments eradicated from the system. The recessive genes which are commonly found in humans have been manipulated in such a way as to bring about the best possible combination. The RNA was also manipulated to allow for a greater transmission of signals.

The mutation has some severe side effects. Chief among them is sterility. As the gametes of the reproductive system consist of 'half-cells' using split DNA, they are perceived as 'damage' by FEV, which repairs them, rendering the mutants sterile. Super mutants are unable to reproduce with any creature, whether clean or mutated. Other side effects include an alteration of pigment of the epidermis. While the super mutants originating from Mariposa are sterile, they do not lose their sexual organs. In contrast, the Vault 87 strain of FEV causes the subjects to lose most of their visible sexual identifiers. Interestingly enough, they lack toes. (As seen on the subjects floating in tanks of fluid at Raven Rock.)

While they won't die due to cellular aging, they are prone to senility, leading to tendencies to engage in aggressive attacks against other humans and other creatures. As those created by the modified strain of FEV as part of the Evolutionary Experimentation Program age, they grow consistently larger and stronger, eventually reaching heights of up to 2 stories.

West Coast mutants
The Mariposa super mutants are a variety of super mutants common on the West Coast and in the Midwest that originated from the Mariposa Military Base in California. While some of them can be rather stupid, in general they are more intelligent and civilized than their distant Vault 87 cousins.

History
Super mutants were first created on the West Coast by Richard Grey, also known as "The Master", who led the expedition to Mariposa Military Base in 2102. When the expedition was attacked by robots, he was himself dipped in a FEV vat, and managed to crawl out. FEV was initially meant to be injected into humans, but Grey soon found out that direct physical contact worked as well. He began to mutate in horrible ways, turning into a blob of flesh-like material. He developed psychic powers, which were enhanced by consuming living minds to expand his own brainpower. Slowly, as wanderers made it into the base themselves, he started doing his own experiments with FEV. Grey — who now called himself "the Master" — lamented the needless destruction of the Great War. In his warped state, he decided that he would have to force humanity to evolve. If everyone could be as perfect as his super mutants, there would be no more conflict. Those who would not evolve would be sterilised and allowed to live their lives in peace. Around 2155, the Master began seeking out uncontaminated humans with which to create mutants and build his super mutant army.

In 2162, a person known as the Vault Dweller destroyed the mutant army by causing an explosion in the FEV vats at Mariposa, which collapsed the entire base, after which he proceeded to The Cathedral and killed the Master. Without the leadership of their creator and his lieutenant, the mutants divided into at least three factions. Some decided to leave California and find a place for themselves somewhere in the East, some wanted to continue the Master's work and dominate the Core Region once again. Others remain in the Core Region and try to make peace with humans, work together to rebuild the world after the War. Broken Hills is the most notable example.

The faction that traveled East eventually settled in the Midwest, forming what was known as Gammorin's Army, and many of them eventually ended up joining the Midwestern Brotherhood of Steel.

In 2236, the Enclave discovered the remnants of the Mariposa Base. Soon, assault squads combed the desert for slaves they could use to mine the military base and get to the Vats. In 2237, having obtained the FEV data, the Enclave abandoned the site after more mutations occurred, causing second generation of Mariposa super mutants to arise - the Enclave left a single squad behind to wipe out the super mutants, but the mutants, using armaments they have cached in the base during excavation, reduced the squad to ashes after suffering heavy casualties. The remaining 1st and 2nd Generation super mutant slaves were sealed inside the base by Enclave sappers, who collapsed the entrance to the base. Inside, the mutants formed a new community.

East Coast mutants
By 2277, the Super Mutants have appeared on the East Coast of the United States. These Super Mutants were created in the Evolutionary Experimentation Program, the experiment assigned to Vault 87. The modified strain of FEV which created these mutants resulted in a new strain of Super Mutants which, in addition to becoming senile, grow larger and stronger as they age. They are different as they are green-yellow in skin color and less intelligent, but look more "healthy" than the western Super Mutants, as they are never seen with any cybernetic parts or organic disorders. Every Super Mutant's facial expression is permanently set in a sneer. However, unlike their counterparts, they are less human, and after the transformation no clues on how they looked in their former lives could be found. They take prisoners to transform them into more Super Mutants. Just like on the West Coast, the by-product of the Vault 87-based creations are Centaurs, who act as watch/attack dogs. East Coast super mutants may possibly have been raiders because the armor they are wearing is similar to that of raiders.

History
During exploration of Vault 87, information from a terminal reveals more about the process of mutation that Super Mutants go through, at least when it comes to the specific strain of FEV found in the Super Mutants of the Capital Wasteland. As a human mutates, its muscular and skeletal systems develop rapidly, while their mental faculties diminish. Most sexual characteristics are eliminated, transforming the subject into an almost asexual state.

Despite their lack of intelligence (even when compared to the least intelligent of West Coast mutants), they are somehow able to organize themselves into a coordinated army (as evidenced by numerous raids and the attempt to reinforce their positions at the Capitol which led to the attack on GNR), procure large amounts of advanced weapons, ammo, and equipment, and even maintain the FEV infrastructure necessary to transform humans and increase their numbers. How they are able to pull this off is never explained as the player never meets a leader or governing body in the game.

An unlikely possibility is that some of the violent mutants have retained their intelligence just like Fawkes and Uncle Leo, but that unlike these two they either lost their sense of morality or they may have been evil humans before being changed (i.e. they did not have any morals). Yet another possibility may be a hive mentality amongst their kind.

In the ruins of D.C., the super mutants are looking for F.E.V and Humans to expand their army.

If You Go To The Citadel And Look In The Pentagon Terminal It Will Tell You That The Super Mutants Of Vault 87 Were Made As Super Soldiers And Were Going to Be Shipped Off To China During The War. It May Be That The Mutants Think They Are In China And That Is Why They Are So Hostile To Locals And Anyone Except Each Other.

Appearances in games
Super mutants appear in all Fallout games.