Human

Humans (Homo sapiens) are a sapient species native to Earth. They are upright tetrapods who primarily use their forelimbs for object manipulation, with their rear limbs reserved for locomotion. They are one of the newest players in the larger meta-civilization of the Orion Arm, having achieved slipspace-using status independently in the 24th century. The largest and most notable human polity is the United Earth Government, often represented by its spacegoing and military arm, the United Nations Space Command.

Humans have been identified as Reclaimers by some Forerunner constructs, hinting at a possible connection between humanity and the ancient civilization. The exact nature of this connection is pending more research into the Halo Event and the nature of the galactic biodisplacements that occurred in the Conservation Measure.

Origins
The remote descendants of arboreal primates, humans supposedly evolved to their current form in the plains of Eastern Africa around 300,000 years ago. The early humans mostly lived as nomadic hunter-gatherers, mainly relying on their intellect, tool use and endurance as survival strategies. A range of related sapient and protosapient hominid species existed alongside Homo sapiens up until relatively recently, but these close relatives went extinct or hybridized with H. sapiens prior to the formation of large-scale civilizations.

Circa 97,445 BCE, humanity was indexed and archived on the Ark by the Forerunner known as the Librarian, alongside the entirety of Earth's sentient biota, in preparation of the imminent firing of the Halo Array. This discontinuity was previously noted in human science as the Ross-Ziegler Blip, and has since the Human-Covenant War been associated with the Conservation Measure and the Halo Event. This roughly coincided with humans' migration out of Africa, which eventually led to their settlement of most of Earth's continents. Beginning circa 10,000 BCE, a cascade of development known as the Neolithic Revolution precipitated the invention of agriculture and the creation of increasingly organized societies. This led to many of the formerly nomadic human communities settling down, and the increasingly available food sources enabled the growth of cities and populations, eventually forming entire civilizations with sophisticated cultures, religions and social structures.

Since the 19th century CE, human societies began to advance rapidly with the Industrial Revolution bringing forth mass manufacturing and many new technologies, resulting in sweeping changes which resonated throughout the globe. This period was marked by rapid technological advancement and ideological experiments, which often proved a volatile combination. The First and Second World Wars in the first half of the 20th century saw death tolls unheard of in previous wars, along with humanity's entry into the Atomic Age with the development of the nuclear bomb. The end of World War II also saw the formation of the United Nations by the victors of the war, with the stated goal of preventing similarly destructive wars in the future; in several decades, the UN would become the preeminent forum of global dialog. The second half of the 20th century was marked by the the Cold War, a period of heightened tensions between two ideologically-opposed major power blocs among the former Allies of World War II: the United States and the Soviet Union, along with their respective allies and proxy states. The Cold War came to an end with the collapse of the Soviet Union in 1991. Around the same time, the rapid advancement of miniaturized computing and the rise of the Internet as a global information network characterized what was known as the Information Age.

The 21st century saw humanity's first serious forays into space colonization, with the relatively rapid settlement of Luna and Mars in the first half of the century ushering in what was later fondly remembered as the Golden Age of Space Colonization - an unprecedented gold rush into the Solar System as numerous actors sought to exploit its near-infinite riches. This period of optimism, technological advancement and prosperity lasted for the better part of a century, until it came crashing down with the mounting of various political and ecological crises on Earth, and finally the ZGene crisis, which had a profound negative impact on the interplanetary colonies. Since the early 22nd century, humanity entered a downward spiral of economic and social problems, wars, and ideological radicalization, culminating in the Interplanetary War between the UN and several political extremist movements, most notably the Frieden and the Koslovics. The war led to enormous devastation on both Earth and the off-world colonies. Such was the magnitude of the crisis that most member nations of the UN willingly gave up their sovereignty in order to manage the crisis and its aftermath, leading to the formation of both the United Nations Space Command and the United Earth Government as pan-human military and governing bodies, respectively.

The Covenant War
By the 26th century, humanity's nascent interstellar civilization was rapidly spiraling into a series of civil wars known collectively as the Insurrection. While regarded as a grave threat to the cohesion of human civilization, the conflict was quickly overshadowed when the alien hegemony known as the Covenant declared a war of extermination on humanity in 2525. For twenty-seven years, humanity fell back world by world, with billions of lives lost to the Covenant's ruthless onslaught. At humanity's darkest hour, an unlikely and unforeseen chain of events ultimately allowed the species to narrowly avoid certain extinction. Shortly after the discovery of the ancient Halo Array, a civil conflict within the highest levels of the Covenant led to a major break-off faction of the hegemony allying themselves with the UNSC, enabling them to eliminate the Covenant leadership, throwing their remaining loyalists into disarray. By early 2553, humanity emerged from the war battered and beaten, but with the immediate existential threat to humanity eliminated. The leaders of the UNSC made a peace treaty with representatives of the Schismatic faction, who would eventually go on to become the Concord of Reconciliation - the UNSC's most powerful ally in the wider stage of the Orion Arm.

After a period of uncertainty known as the Years of Disquiet, humanity began to take steps toward recovery thanks to the efforts of the Phoenix Initiative, an interim coalition formed by the UNSC to facilitate reconstruction. This era was known as the Reconstruction Period, lasting from the 2550s well into the late 2570s. This period saw the reclamation of various lost colonies, the resettlement of various displaced populations, the gradual rebuilding of the UNSC's naval capability, as well as a number of technological advances. It also marked the beginnings of humanity's integration into the overall civilization of the Orion Arm and coming to terms with their status as but one species among many.

Humans are variously characterized by other species as persistent, inventive and resourceful, but also arrogant, myopic and boorish or culturally aimless. Within the Covenant, they are commonly compared to the Unggoy and especially the Kig-Yar. While increasing numbers of Sangheili came to respect humanity as worthy foes during the Human-Covenant War, many continued to have reservations about letting them remain independent of Sangheili rule. Humans' ubiquitous use of artificial intelligence remained a particular point of contention due to both longstanding Covenant strictures against AI and objections about overreliance on machines.