The Stargate franchise has created many different kinds of aliens, though a lot of them share a definitive characteristic: they are humanoid in appearance and anatomy. Like many other sci-fi series, the budgetary constraints of Stargate have led to imaginative justifications for their human-looking aliens. The reason most extra-terrestrial natives look human is due to a primeval race called the Ancients, whose technology and exploration led to the universe as we know it in the Stargate franchise.
The Ancients are foundational to the Stargate universe, and it is proven in every series. In Stargate SG-1 it’s revealed that the Ancients built the Stargates, and seeded the Milky Way galaxy with human life. In Stargate Atlantis, the lost city of Atlantis is shown to be an Ancient repository of knowledge. Finally, in Stargate Universe, the spaceship Destiny is a galaxy-hopping remnant of the Ancient people. Their technology, philosophies, aesthetic and spirituality are integral to the main TV series and sequel movies.
The Ancients began as a race known as the Alterans, evolving to an advanced civilization millions of years ago in a distant galaxy. A religious schism split the culture into Alterans and a sect called the Ori, fanatics who sought the domination of races they considered beneath them. The Alterans relied on science and technology, while the Ori preferred to glorify the method of spiritual ascension known only to their people. The Alterans migrated to the Milky Way galaxy, and seeded many planets – including Earth – with the beginnings of human evolution. After a plague in the Milky Way wiped out most of their people, the Alterans moved to the Pegasus galaxy, using Atlantis as a cultural hub and seeding even more worlds with human life.
Atlantis was originally a massive ship, which the Alterans flew from the Milky Way to the Pegasus. These immigrants became known as Lanteans, and they lived peacefully for millions of years, helping thousands of worlds evolve. Their exploration accidentally resulted in a new enemy, a race that came to match them in technology and ambition. The human life they spread encountered Iratus bugs, vampiric creatures whose new source of food made them grow into super-predators known as the Wraith. The following war ended when what was left of the Lanteans submerged Atlantis, and returned to Earth to interbreed with Stone Age humans. Some of their older ships, however, remained on pre-set routes through the universe, continuing to explore and seed worlds. One of these was named the Destiny, which was rediscovered a decade after the two Earth Stargates.
Stargate SG-1 began because of the most important Ancient architecture left: the Stargates. The show also invokes the power of the Ancients on life-or-death occasions, with the characters usually referring to them when they seek Stargate-adjacent technology or knowledge. Stargate Command also has a constant need for new weaponry to utilize against the immediate Goa’uld threat. The Asgard reveal the status of the Ancients as the earliest advanced civilization in the universe, and their membership as one of the Four Great Races, as well as their method of spiritual ascension, which saves the life of Daniel Jackson. Later in the series, after Atlantis is found, the original show delves into the Ancients’ history more, and the wisdom that can be exploited defeat foes like the Ori.
Stargate Atlantis takes place in and around the Ancient city of Atlantis, and features a human expedition, populated by military officers and scientists from multiple Earth nations. The city is the headquarters of an operation that is similar to the program pioneered by SG-1 – namely, to explore alien worlds and report back on their findings. Much like SG-1, the Atlantis team’s missions are made more urgent by the appearance of an old enemy. The Wraith have managed to terrorize the Pegasus galaxy for hundreds of thousands of years prior to the resurgence of Atlantis, and the new human contingent are tasked with stopping them. Ancient technology becomes crucial for them, as it is the only thing known to repel the Wraith.
Stargate Universe focuses on the adventures of an Ancient ship known as the Destiny, which was built to investigate the farthest reaches of the universe. The Destiny was pre-programmed to follow seed ships, which were designed to build Stargates on the planets deemed fit to host human life. The original goal of the Destiny was to study plausible sentience in cosmic radiation, but as the Ancients started ascending, they lost interest in pursuing it. The Destiny gets a modern crew after the Icarus Project – a part of the Stargate program – unseals the ninth chevron of the traditional Stargate sequence. The project’s staff are forced into manning the ship to escape a battle with the Lucian Alliance, leading to a years-long trip to the end of the universe. Like in Atlantis, the crew becomes surrounded by and dependent on Ancient technology.
Stargate Atlantis also features the revelation of the Ancient Technology Activation gene, a part of some humans’ genetic makeup that makes them compatible with using Ancient technology. The ATA gene was passed down from the Alterans’ interbreeding with early humans, not just on Earth, but on many seeded worlds across the universe. The gene allows its carriers to interact telepathically with the most advanced Ancient equipment, particularly piloting Ancient vessels. John Sheppard, Jack O’Neill, and Dr. Carson Beckett were among the few natural gene carriers in the Stargate program, making them invaluable when a situation demanded the control of Ancient ships and weaponry. Dr. Beckett's ATA gene therapy on non-carriers made it possible for even more people to harness control of Ancient technology.
The revelation of the Ancients as a borderline omniscient presence within the Stargate universe elevated the material of the series. Such a culture provided an explanation for the many human-centric societies the Stargate program encountered. It also allowed each series to develop the franchise, as more and more Ancient technology, enemies, and architecture were discovered.
The original Stargate movie launched the universe by hinting at the Goa’uld, an old race that was already far beyond humanity’s technological advancement. Stargate SG-1 and its successive shows proved that the real wonder was not in the manipulative tactics of the Goa’uld, but in the machinery the aliens appropriated in order to travel. The Ancients’ legacy was not in city ruins or weaponry, but in the Stargates, which their descendants used to meet one another, work together, and progress to a brighter future.