- "The greatest resource our Holy Imperium possesses is the fathomless multitudes of humanity itself. No power is mightier and no force more dreadful when turned to a single purpose. By human hands alone we have remade stars in our image. By this token the wise know that true power lies in the mastery of blood and bone, in the very meat of mankind."
- — Quastor General, Brantus Hurst, Departmento Munitorium Penitential Command
The Human race (Homo sapiens), also known as humanity, Mankind or Man, is that collection of factions comprised of humanity, the most dominant intelligent race in the Milky Way Galaxy in the late 41st Millennium AD. Humanity is the only species (other than the Eldar) who are not solely represented by one army within the Warhammer 40,000 universe. Instead, humanity is divided into a multitude of factions, either working for or against the overall interests of Mankind in its attempts to retain control over the galaxy and survive unscathed in an incredibly hostile universe.
Humans originated on the planet Terra (Old Earth), and first colonised the galaxy during the Dark Age of Technology. Almost nothing is known about human civilisation in this time, this information having been lost in the utter chaos of the following Age of Strife. In the late 41st Millennium the majority of humans are part of the Imperium of Man, although other human civilisations are known to exist. Unfortunately, humanity is known to be a species that is relatively easy to corrupt to the service of Chaos and in fact, it is Mankind's dominance in the galaxy that has shaped the Warp and the form the Chaos Gods currently take, as they are ultimately no more than psychic manifestations in the Immaterium of the collective psyches of the intelligent species of the galaxy.
Unlike the ancient Aeldari, humanity has only just begun the evolutionary transition into a fully psychic species. As yet, very few humans out of the entire population of trillions present in the galaxy develop the genetic mutation that allows them to become psykers, though this number is slowly increasing as the centuries pass. However, most human psykers lack the mental discipline or inner strength to prevent themselves from becoming daemonhosts or otherwise being manipulated by the dark entities of the Warp.
Humans, known taxonomically as Homo sapiens (from the ancient language of the Roma which meant "wise man" or "knowing man"), are the only living species in the Homo genus of bipedal primates in Hominidae, the great ape family. Anatomically modern-appearing humans originated on the world of Terra about 250,000 standard years ago, reaching full behavioural modernity only around 90,000 standard years ago.
Humans have a highly developed brain, capable of abstract reasoning, language, introspection, and problem-solving. This mental capability, combined with an erect body carriage that frees the hands for manipulating objects, allowed humans to make far greater use of tools than any other living species on Old Earth. Other higher-level thought processes of humans, such as self-awareness, rationality, and sapience, are considered to be defining features of what constitutes a "person", though such features are shared with the other major intelligent xenos species of the galaxy like the Eldar, the T'au, the Necrons, and the Orks (though some might question the latter).
Like most higher primates originally native to Terra, humans are social animals. However, humans are uniquely adept at utilising systems of communication for self-expression, the exchange of ideas, and organisation. Humans create complex social structures composed of many cooperating and competing groups, from families to nation-states to interstellar empires. Social interactions between humans have established an extremely wide variety of values, social norms, and rituals, which together form the basis of human society. With humans present across the galaxy and having adapted to every possible environment, they are currently the galaxy's dominant species. The current population of humans in the Milky Way Galaxy in the 41st Millennium AD is unknown, but numbers in the many trillions, if not quadrillions.
Humans are noted for their desire to understand and influence their environment, seeking to explain and manipulate phenomena through science, philosophy, mythology, and religion. This natural curiosity has led to the development of advanced tools and skills, which are passed down culturally, though cultural stagnation or even retrogression is possible, as the grim history of the Imperium of Man over the last 10 millennia so readily demonstrates.
According to Imperial savants, human history has progressed through several different distinct periods, which chronicle the race's rise to ultimate dominance over the Milky Way Galaxy and the current situation in which humanity faces a number of extinction-level threats from Chaos and multiple, deadly xenos species. These periods include:
- Age of Progress
- Age of Technology
- Age of Strife
- Unification Wars
- Great Crusade
- Horus Heresy
- Age of the Imperium
The Restoration of Humanity
By the time of the Unification Wars that established the Emperor of Mankind's rule over Terra, the human homeworld's population had suffered through the horrors of the Age of Strife, a period punctuated by constant warfare and the use of weapons of mass destruction that had badly damaged the environment of Old Earth. Under the Emperor's rulership, humanity would be restored, intellectually, spiritually and physically to the heights it had once known, and the shackles of darkness cast aside. The war continued without relent until finally all of Old Earth's techno-barbarian factions, nations and fractured city-states pledged the Emperor fealty and at last Terra was unified for the first time in many millennia.
It was not enough merely to secure military victory, however -- the betterment and restoration of humanity required more. So it was that even before victory on Terra had been achieved the Emperor and those learned souls He had gathered to Him started to experiment with genetics. This was done first and foremost to stabilise the population and to recreate the race of Mankind as it was before the radiation storms and generations of viral and alchemical weapons had wracked the planet. Secondly, the creation of genetically augmented transhuman fighters that had begun with the Thunder Warriors who had fought in the Emperor's armies continued apace into newer, more powerful creations, ultimately leading to the genesis of what would later become known as the Space Marine Legions. But in truth, the Emperor's greatest work was nothing less than the purging of Mankind's own genome, and its restoration to a baseline of what could be considered truly "human" as that term had been defined before the Age of Strife.
When the Emperor's Great Crusade moved out into the broader galaxy, many human colony worlds would be discovered where the human genome had drifted, resulting in unusual physical manifestations. In most cases, there were nothing more than evolutionary adaptations to the local planetary environments, and resulted in unusual skin tones, eye and hair colours and otherwise meaningless cosmetic changes. However, certain populations were discovered whose genomes had shifted in radical directions from the human baseline, either through environmentally-derived mutation, xenos alterations or self-imposed genetic engineering. In these cases, the Emperor was forced to make a choice as to whether these mutants still retained the essential quality of humanity, or had moved beyond the pale, having been transformed into what was actually a new species of xenos. In certain cases, such as those of the so-called "Abhuman" strains such as the Squats, Ogryns and Ratlings, the Emperor judged them to be recognizably human enough to be incorporated as valuable members of Imperial society. But in many other cases during the Great Crusade, many populations failed to make the cut, and were judged to have become so alien that they needed to be treated as true xenos, with the Space Marine Legions deployed to carry out the resulting purge. The galaxy would belong to humanity, but it would be the same humanity that the Emperor had loved and served for most of His long life.
Imperium of Man
The majority of humans exist within the Imperium of Man. The Imperial Cult preaches that humanity has a Manifest Destiny to conquer the entire galaxy, to the point where intelligent alien species are seen as inferior and worthy of nothing but extinction.
The Lost and the Damned
The next greatest concentration of humans in the galaxy after the peoples of the Imperium exist as the Lost and the Damned of Chaos, and reside primarily, though not exclusively, within the Warp rift called the Eye of Terror. Not a coherent civilisation as such, they exist as part of a diverse and infinite collection of warbands and hosts under the leadership of Chaos Champions. Due to the nature of the Warp, some of these humans are the original Imperial subjects who sided with the Warmaster Horus during the Horus Heresy over ten thousand standard years ago, though their number has been greatly supplemented by more recent humans who have turned to the worship of Chaos, or slaves captured as part of the many Chaos raids out of the Eye into Imperial space.
Less xenophobic than the Imperium, though no less convinced that it should dominate the galaxy, the T'au Empire has no qualms about letting other intelligent races join it. Whilst few in number, some humans have done so and exist within the Empire where they are known as Gue'vesa. These humans, for the most part, are the descendants of Astra Militarum troops who were abandoned in T'au space during the Damocles Gulf Crusade and in other conflicts between the Imperium and the T'au Empire; however, it is not unheard of for Imperial planets like the desert Mining World of Taros to want to secede from the Imperium to join the T'au Empire.
Other human civilisations in the Milky Way Galaxy are extremely rare. This is mostly due to the fact that the Imperium of Man considers itself to have an automatic right to rule all of humanity wherever humans live in the galaxy, and it ruthlessly suppresses any attempt to secede from it. Similarly, any lost human colonies that are rediscovered from the Dark Age of Technology are also incorporated into the Imperium whether they want to be or not. Despite this, a few independent human civilisations have been known to exist in the furthest reaches of the galaxy.
When the Age of Strife descended on the galaxy and Warp travel and astropathic communication became impossible, the majority of human colonies were cut off from Terra and forced to survive on their own. In some cases this meant that they devolved into considerably more primitive societies as the knowledge to create and maintain much advanced technology was lost. The Great Crusade reunited many thousands of lost human colonies back into the Imperium of Man, yet every now and then changes in the flow of the Warp mean that new human colonies are unexpectedly discovered. Whilst nobody can know for sure how many, there are almost certainly more colonies still cut off from the rest of humanity, waiting to be discovered.
The Imperium keeps a tight grip over its planets, yet every now and then a world does attempt to secede from the Imperium. This may be the result of the Planetary Governor believing he can get away with independence, or it may be the result of a revolution that deposes those in power. Many of these secessions are orchestrated by the Ruinous Powers of Chaos, and the humans that are part of these rebellions should be counted as the Lost and the Damned, though there are also occasions when a planet decides it wants to be independent of the Imperium through its own volition. Regardless of the cause, these independent realms rarely last for long as they are swiftly and brutally subjugated back into the Imperium, even if it takes decades for the ponderous Administratum of the Imperium to get around to assigning the necessary military forces to suppress the rebellion.
The only independent human civilization with any real sustainability outside the Imperium of Man, some humans evade the Imperium's clutches and live outside of its reach in bands of starships existing through raids and piracy. Often allying themselves with Eldar or other xenos, these humans are swiftly executed as heretics or traitors if they are caught by the Imperial authorities.
Other Human Species
Throughout the long history of the Imperium and before, the human race has mutated into a variety of different stable species as a result of different populations' adaptation to various environments across the galaxy over the millennia. These variant human species are known as Abhumans. Abhumans are tolerated to a varying degree within the Imperium due to the fact that they are seen as being close enough to the baseline human genome to still be accepted as children of the Emperor.
Imperium of Man
- Imperial Guard - The backbone of Imperial military might in the 41st Millennium, the Imperial Guard are not a single, cohesive fighting force but are rather a vast military force comprised of a wide spectrum of different equipment, tactics and doctrine depending on the particular star system from where an Imperial Guard Regiment originates. Because they are formed in this way, recruited and equipped by the resources available in their particular home star system and home sector, the Imperial Guard are the largest single fighting force in the galaxy and they number in the billions of soldiers, all willing to die in the name of the Emperor of Mankind.
- Space Marines - The Space Marines are genetically-modified superhuman warriors designed specifically to lead the human reconquest of the galaxy during the Great Crusade that created the Imperium of Man over ten thousand years ago during the 30th and 31st Millenniums. Since the Horus Heresy, the Space Marines have adopted more of a defensive role, fighting alongside the regiments of the Imperial Guard and aiding them when they need help in the most difficult situations. Space Marines also fight as individual 1,000-warrior-strong Chapters, seeking their own conflicts and resolving them in turn.
- Sisters of Battle (Orders Militant of the Adepta Sororitas) - The Sisters of Battle are the least common human army on the battlefield because they were created specifically to fight Imperial heretics and rebels and just as only human males can be Space Marines, only human females may serve among the Sisters of Battle. They serve as the military forces of the Adeptus Ministorum, better known as the Ecclesiarchy, the ecclesiastical bureaucracy which administers the star-spanning Imperial Cult of the God-Emperor. The Sisters also serve as the Chamber Militant of the Imperial Inquisition's Ordo Hereticus, tasked with combating the enemies of the Emperor who exist within the Imperium.
Forces of Chaos
- Chaos Space Marines (Traitor Legions) - The most hated enemies of the Imperium, the Heretic Astartes were once normal Space Marines, fighting together with the other Loyalist Space Marine Legions in the Emperor's name to build the Imperium of Man in the course of the Great Crusade, but they betrayed the Emperor and turned to the service of the Ruinous Powers of Chaos during the Horus Heresy. Unlike the Loyalist Space Marines, the Chaos Space Marines work more closely with their strong network of allies such as Warp daemons, human Chaos Cultists and Traitor Imperial Guardsmen, relying on them more often than the Loyalist Space Marines rely on the Imperial Guard. The Chaos Space Marines are still organized into the original First Founding Space Marine Legion structure, unlike the Loyalist Space Marines who were divided into 1,000-man-strong Chapters after the Horus Heresy during the Second Founding of the Space Marines. The Second Founding was spurred onwards by the adoption of the Codex Astartes, which was written by the Ultramarines Legion's Primarch, Roboute Guilliman.
- The Lost and the Damned - The Lost and the Damned of Chaos reside primarily, though not exclusively, within the great Warp rift in the Segmentum Obscurus called the Eye of Terror. The Lost and the Damned exist as part of a diverse and infinite collection of Chaos warbands and hosts under the leadership of Chaos Champions who are usually, but not always Chaos Space Marines belonging to one of the Traitor Legions. Due to the temporal nature of the Warp, some of these humans are the original Imperial citizens who sided with the Warmaster Horus during the Horus Heresy over ten thousand standard years ago, though their number has been greatly supplemented by more recent humans who have turned to the worship of Chaos, or slaves captured as part of the many Chaos raids out of the Eye into Imperial space.
- The Horus Heresy - Book One: Betrayal (Forge World Series) by Alan Bligh, pg. 15
- Warhammer 40,000: Chapter Approved - The Book of the Astronomican
- Warhammer 40,000: Rulebook (5th Edition)
- For The Emperor (Novel) by Sandy Mitchell