The Quarian hail from the world of Rannoch. Long ago, they seemed to have been a technologically capable species. It came to a point that they started creating machines known as Geth. When creating a Geth, they made sure that the machine had less intelligence than that of an average AI. Because of this, many of the Geth became servants to the Quarians. However, as the tasks became more complex, the Quarian found themselves in the situation they wanted to avoid. Some of the Geth had acquired consciousness.
In a state of panic, the Quarian government demanded the extermination of all Geth. However, not all Quarians supported the notion. Because of this, it plunged Rannoch into civil war. When the Geth-sympathizing Quarians were eliminated, many of the Quarians thought of them as Geth as well.
But what they didn’t expect is how far the Geth had grown. Their neural network expanded all over Rannoch and allowed them to communicate with each other. The Quarian and the Geth waged war against one another with the former losing. Billions of Quarians died and the survivors only managed to escape simply because the Geth no longer saw them as a threat. However, it is because of this war that the Quarians were stripped of their position in the Council and became nomadic in nature.
The Quarians are slightly smaller than humans. However, they have the most human features in comparison to many of the alien races. They also have a similar life-span to Humans and Turians. Like all the races (save for the Kett), all Quarians have an endoskeleton. The Quarians also have lips, teeth, and two eyes with eyelids and tear ducts. They also have three thick fingers on both hands which include a thumb, an index finger, and a long finger, similar to the middle fingers for humans, as well as three toes on each foot.
However, they do have a sad immune system. Anything infection or allergy that hits them can decrease their lifespan drastically. Because of their bad immune system, they are also unable to mate properly which denotes low birthrate. This is one of the similarities they have with the Krogan, save for that the Krogans had intervention.
Despite their reduced numbers, Quarians as much as possible only have one child per family. This is to ensure the zero population increase. But if they find their numbers dwindling, the Quarian government will temporarily lift the ban and give incentives to those who have more children. Because of this, families are small and close knit. They focus only on two things: survival and sustainability.
Ever since the loss of their home world, Rannoch, they focus on serving the Migrant Fleet. All their laws and beliefs center on the Migrant Fleet. Because of their tightly knit society, the Quarian believe in depending on his or her crewmates to survive. They are much more collectivist or community minded individuals than the Krogan or the Humans.
They value three qualities: loyalty, trust, and cooperation. Even in their ancient past, they were very emotional people.
Notable Quarian Characters in Mass Effect: Andromeda