Template:Infobox Race Template:Quote The Alterans were an extraterrestrial species from the planet of Celestis in the Alteran Home Galaxy that evolved millions of years ago. Because of a philosophical disagreement, they would eventually split into two factions: the Ancients/Ancestors/Lanteans and Ori, where the Ancients went to the Milky Way which they called Avalon and the Ori remained in the original galaxy. In their later history, they seeded human life in their respective galaxies, especially the Ori.
Template:QuoteTens, possibly even hundreds, of millions of years ago, the Alterans (the first evolution of humanity) lived together as one society in a distant galaxy along the evolutionary path to Ascension. However, a philosophical division soon emerged among the Alterans, dividing them into two factions: the Ancients/Ancestors/Lanteans, who came to rely more heavily on science and rationality, and the Ori, who continued to become more and more fervent in their religious beliefs. Merlin indicated however, that when the Ori started out they had good intentions which had become corrupted.
Ultimately, the Ori became so extreme in their beliefs that the two factions split apart and began to oppose each other, culminating in the Ori attempting to wipe the Alterans out. The Alterans were too few in numbers, however, and were ultimately forced to hide their ways. Though they considered using their knowledge to defend themselves, they faced a war of attrition, one they ultimately believed that they could not win. To avoid genocide, the Alterans built a ship and left their home galaxy, while the Ori remained. After many thousands of years, the exiled Alterans discovered the Milky Way, where they would directly and indirectly influence much of galactic (and intergalactic) history. Because of the history between them the Alterans chose to hide their second evolution of humanity from the Ori. 
The Alterans and the Ori later both Ascended and even on the higher plane the Ori were determined to destroy the Alterans, now known as the Ancients by primitive cultures. Later, the Ori were destroyed by Dr. Daniel Jackson with the help of Merlin and his weapon. SG-1 then used an Alteran device called the Ark of Truth left behind in their old home at Ortus Mallum to show the Ori followers the truth about their "gods" and end their crusade.
Template:QuoteThe Alterans believed in science, reason, and logic. Knowledge and enlightenment were fundamental to their world view. They believed that the universe was to be studied, and that scientific experimentation was essential to gaining understanding. Most importantly, the Alterans believed in free will. To them, the right to believe whatever a person wants is more important than anything else. This has been to their detriment, however, as it has been that very belief in free will that forced them to respect the rights of the Ori in believing their fanaticism. They also believed that they did not have the right to restrict the freedom of the followers of Origin to believe in the Ori by "brainwashing" the true nature of the Ori into their followers for much the same reasons.
The Alterans, being one of the first forms of sentient life to evolve in the universe had developed many advanced forms of technology before they left their galaxy. Ranging from advanced healing technologies, and long-range communication devices, the Alterans were one of the most advanced races in the known universe. They had also developed intergalactic hyperdrive technology long before sentient life had developed on Earth. Another piece of technology they created and ultimately abandoned was the Ark of Truth, a device meant to brainwash the Ori's followers into believing the truth, but abandoned it as they believed it was unethical.
Although the Alterans are human in appearance, their physiology is much more advanced, with a heightened intellect and capacity to store knowledge. It has been suggested by not only Dr. Carson Beckett, but also the Alterans (specifically Janus) themselves, that the human Alterans, those who would later become the Ancients and the Ori, were the first evolution of humanity. It has also been implied that the current human species evolved as such due to the actions of the Alterans and the Ori, since two species progressing along identical evolutionary paths is virtually impossible. The Alterans later created the "second evolution" of their species, in both the Milky Way and Pegasus Galaxy, and it is also likely that the Ori created their own second evolution in their home galaxy to serve as worshipers of the Origin faith.
Towards the end of their evolutionary development, but still before they ascended, the Alterans developed numerous advanced and varied abilities, such as:
These abilities are varied between individuals. Usually not all the abilities listed are present in one individual, but are all potentially possible, including abilities not yet known. The Alterans did create devices which can transfer all or some of these powers to an individual without causing them to ascend, such as Merlin's version of the Repository of knowledge.