Human

Summary
The human race is an Early-Development spacefaring civilization whose original homeworld is Earth, the third planet of the Sol System. Throughout their existence, they have developed their civilization by engaging in food production on a larger scale, developed language, developed religion and political philosophies along with better technology. 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. At time of the Halo series of games and novels, there are approximately 60 billion members of the species living in parts of the Milky Way Galaxy.

Early development on Earth
The Homo sapiens sapiens was believed to have appeared in Earth's fossil record approximately 200,000 years ago (there was another subspecies of Homo sapien, the Homo sapiens idaltu; this subspecies is extinct, but was believed to have lived as long as 160,000 years previous). The current human race is not the only humanoid species known to live on Earth, but the Homo sapien sapien is believed to have displaced all predecessors, including the Neanderthal and the Homo sapien idaltu. The Homo sapien usually stands several feet tall, though this varies depending on nutrition, genetics and other factors. Members of the species, like some Covenant species, is four-limbed and bipedal; they walk on two legs, walk upright and use their arms and hands (complete with opposable thumbs) to hold and manipulate objects.

The development of human civilization as humans recognize it today started from the ability to grow food in a systemic fashion, referred to as the Neolithic Revolution; this took place over 10,000 years ago. The stability that came from systemic agriculture allowed for more permanent settlements and the development of tools to benefit the members of the species. Basic toolmaking, domestication of other species on Earth and trade and communication helped develop societies further, leading to the formation of genuine nation-states over 6,000 years ago. The first such states are believed to have formed in Southwest Asia and spread elsewhere over time. Economic, political and religious advancement continued to come as this species was able to automate many tasks in the Industrial Revolution and its associated scientific breakthroughs at the end of the second millennium. 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 lives and procreated more easily, eventually leading to billions of humans on Earth.

Colonization and War
The species was able to explore space close their home planet in the 20th century, as the population continued to increase into the billions. The subsequent conflicts over resources, economics, religion and politics on Earth 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, releasing the serious pressure on the homeworld.

Generally the exploring and peace-making variety of species after, approximately several centuries of spreading throughout many solar systems and inhabiting hundreds of worlds, they discovered the violent, theocratic Covenant and were forced into the war covered by the Halo games. As the decades-long war continued, the human species has gained the reputation as a worthy adversary against the Covenant. 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 join them. The Elites have even admitted that they are more tactically brilliant than themselves. However, despite great courage and brilliance, the future is dark for the survival of the human race as the covenant continue to wipe out their colonies.

Speculation: Similarities Between The Forerunners and Humans
The Humans are believed to be "evolved" forms of Forerunners in many ways. A crucial clue is given in Halo: Combat Evolved when 343 Guilty Spark says,"Why would you hesitate to do what you've already done?" and "Stop being Human." "Last time you asked me if I would do it would I? My answer has not changed. We must activate the ring." 343 Guilty Spark said those to the Master Chief in Halo: Combat Evolved and in Halo 2 when Miranda Keyes asked "Where would someone go to activate the other rings?" "Why the Ark........of course." 343 Guilty Spark replied sounding rather puzzled at the question, like he was expecting her to know that.(Like how he was also expecting the Chief to know everything about Halo)

However due to the recent web comic that included the character N'chala, this theory becomes very unlikely.

Humain