Human

The Human race is an early-development space faring civilization whose original home world is Earth, the third planet of the Solar System.

Background
Throughout their existence, Humans have developed their civilization by engaging in food production on a larger scale, developing language, developing religion and political philosophies and exhibiting telescoping technological and infrastructural development. They were studying the stars long before they were able to travel out of their atmosphere. After succeeding in space colonization, the human race was able to terraform and inhabit other planets besides Earth, but the human race is under pressure due to the discovery of the caste-driven Covenant after several centuries of space travel. The total population at the end of the war is unknown.

Early Development on Earth
The Homo sapiens were believed to have appeared in Earth's fossil record between approximately 100,000 and 200,000 years ago (there was another subspecies of Homo sapiens, Homo sapiens idaltu; this subspecies became extinct, but was believed to have lived as long as 160,000 years previous). While the exact origins of humanity is a hotly contested paleontological debate, it is likely that the first humans evolved from a genus of upright ape-like hominids called Australopithicenes (ie; Australopithecus).

The current human race is not the only humanoid species known to live on Earth, but the Homo sapiens is believed to have either displaced or merely outlasted all other branches of the genus, including Homo neanderthalensis and Homo sapiens idaltu. Homo sapiens usually stand six feet tall, though this varies depending on nutrition, genetics and other factors. Members of the species, like some Covenant species, are four-limbed and bipedal; they walk upright on two legs and use their arms and hands (complete with opposable thumbs) to hold and manipulate objects such as tools.

The development of human civilization as humans recognize it today started from the ability to harness the growth cycle of plants, producing edible food-energy in a systemic fashion. This time is referred to as the Neolithic Revolution, which occurred first on Earth over 10,000 years ago and soon spread to disparate human groups. The stability that came from systemic agriculture allowed for more permanent settlements and the development of ever-more-complex tools to further benefit the members of the species.

Innervated toolmaking and the domestication of other species on Earth gave human populations greater and greater power to expand their populations, and trade ensured the diffusion of new technologies to adjacent groups. These exploding populations led to the formation of genuine civilizations over 8,000 years ago. The first such sites are believed to have formed in Southwest Asia and Asia Minor, appearing elsewhere soon after. The infrastructure of civilizations continued to expand and grow in complexity as innovative technologies and larger populations allowed for increasing food-energy availability. Economic, political, scientific and religious advancement continued to quicken as this species was able to automate many tasks in the Industrial Revolution.

This automation gave birth to the Digital Revolution, in which computing machines allowed scientific discovery and technological development to accelerate with explosive speed. Larger urban centers and tools for civilian and military uses were able to develop, as were more modern economic and political systems. As these systems developed further, the species was able to enjoy longer, more pro-creative, and more comfortable lives, virtually impervious to other creatures from whose midst they sprang. Thus-unchecked, human population growth eventually led to the presence of several billions more humans on Earth than could be sustained for any long period of time.

Population
It is known that in the 22nd century, Earth was overpopulated, jump-starting the colonization programs of the time. The population of Earth after the Human-Covenant War is unknown. At the beginning of the Human-Covenant War, the population would be estimated at around 58.074 billion. the population after the Human-Covenant War is approximately 200 million, an indication of just how badly the war has gone for humanity.

Explanation
2525 - 1999 = 526. The population in 1999 was 6 billion. The population has risen at a rate of roughly 99 million people per year; 526 × 99 million + 6 billion = 58.074 billion. Note that this is only an estimation.

Colonization and War
The species was able to explore the space immediately surrounding their home planet in the 20th century, as the population began to advance beyond the capacity of the planet to sustain their civilization. The subsequent conflict over resources, economics, religion and politics on Earth gave way to numerous wars. Furthermore these tensions put great pressure on the species in the beginning of the twenty-third century, and the transnational organization that became the United Nations Space Command engaged in more frequent space colonization and sought to represent the entire species, even though no one state ever previously ruled the entire human race. The development of Slipspace travel in 2291 helped the UNSC engage in spreading the human race beyond their home solar system, relieving the serious ecological pressure on the home world.

The typically peaceful species was finally pushed into major conflict, when, after several centuries of spreading throughout many solar systems and inhabiting hundreds of worlds, they discovered the violent, genocidal, theocratic Covenant and were forced into the war covered by the Halo series. As the decades-long war wore on, the human species gained the reputation as a worthy adversary against the Covenant, despite the fact that they were technologically and numerically the Covenant's inferior.

Humans have been able to show great bravery when facing great odds. Some of the members of the Covenant wonder why the Hierarchs had refused to allow the humans to join them, as they had been able to hold steadfast even when outmatched in almost every way. However, despite great courage and brilliance, the future seemed dark for the survival of the human race as the Covenant continued to wipe out their colonies.

March 3rd, 2553, saw the end of the Human-Covenant War as a victory for humanity and their newfound Sangheili allies - the majority of the Loyalist Covenant military having been defeated at Delta Halo by the Sangheilian Fleet, and the rest annihilated by the joint Elite-UNSC forces at the Ark. This victory came in time to save the human homeworld, thanks chiefly to the actions of the Arbiter and Spartan, John-117.

Similarities Between The Forerunners and Humans
A common speculation by fans is that the Forerunners may be ancient ancestors of Humanity. Examples of possible similarities include comments made by 343 Guilty Spark during Halo: Combat Evolved, and Halo 2 by 2401 Pentient Tangent. In both games, the Monitors convey confusion about the ignorance of the humans about the Halo array. Halo 3 gives the most evidence for the theory of humans being Forerunner, or at least Forerunner descendants, and much of it requires little speculation or interpretation. 343 Guilty Spark says verbatim to the Master Chief:

"You are the child of my makers. Inheritor of all they left behind. You are Forerunner." -343 Guilty Spark to Master Chief

The High Prophet of Truth also tells Sergeant Major Johnson: "Your Forefathers wisely set aside their compassion. Steeled themselves for what needed to be done. I see now why they left you behind. You were weak. And gods must be strong." However due to the recent web comic that included the character N'chala, this theory becomes less likely. It became impossible due to the Server 05 message and the Terminals in the Iris viral campaign stating that the Forerunners discovered humanity on a planet in a "perilous location beyond the line" (possibly meaning that Earth was outside of the Forerunners' protection but the Librarian built a portal to the Ark before the Didact fired the array) and built the Ark to protect humanity from the activation of the Halos and the Flood. As shown with the Bestiarum, the Forerunners worked to categorize species that they found. Humanity then, was NOT created by the Forerunner.

Another theory (one supported by the Halo 3 Terminals) is that the humans became the inheritors of the Forerunner empire and technology because the Forerunners passed the Mantle of Guardianship down to humanity, as it was passed to them, presumably from the Precursors. (see Reclaimer for more).

Another smilarity is on the level Sacred Icon, when you deactivate the plug locks then a holographic hand comes up and it looks just like a human hand. This implies Forerunner technology was implied for Human use.

A final theory serves as somewhat a compilation of the above theories, and is can be supported by much of the same evidence: The Forerunners may have found the humans on the planet Earth, and bred with them, making today's humans part of the Forerunner lineage, and particularly important to be protected by the Forerunners.

During the events in Halo: Contact Harvest, Covenant religious vehicles traveled the edge of Covenant-controlled space and discovered a planet that was covered with Forerunner technology glyphs. A Brute Chieftain known as Maccabeus (Tartarus' uncle) landed on the planet (Harvest) and was, at first, friendly to the humans. It wasn't until a shot rang out did things turn bloody. Later, a report of the planet's glyphs was sent to the Vice Minister of Tranquility (Regret). He took the information to the Minister of Fortitude (Truth) and they went to see the Oracle (the Forerunner AI in the Dreadnought).

Upon activation of the Oracle, the AI exclaimed, "FOR EONS I HAVE WATCHED. LISTENED TO YOU MISINTERPRET. THIS IS NOT RECLAMATION. THIS IS RECLAIMER." After those words, the glyphs in the report were shown and they began to transform shape until a crude image of a human appeared. The Oracle adds, "AND THOSE IT REPRESENTS ARE MY MAKERS. I WILL REJECT MY BIAS AND WILL MAKE AMENDS. MY MAKERS ARE MY MASTERS. I WILL BRING THEM SAFELY TO THE ARK."

After that, the power conduits aboard the Dreadnought short circuit as several frying, dead Lekgolo worms fall out of the spaces. The Dreadnought powers down. Truth, believing that the humans were actually Forerunner, believed this information could destroy the foundation of the Covenant, and, with it, his power. Upon being promoted (through blackmail) to High Prophet, he used his power to set out a massive genocide against the humans.