Although the manga does not tell of the Origins of the Saiyan race, the complete history of the Saiyans was revealed in the anime where it is discussed heavily during the Vegeta saga, as well as in the OVA Plan to Eradicate the Saiyans. It is also a central theme in the Baby saga of Dragon Ball. This causes for three different explanations as to the history of the race. Saiyan's arrival on Planet Plant as seen in Dragon Ball GT During the Vegeta Saga of Dragon Ball Z, King Kai describes the Saiyans as a group of barbaric aliens who shared a planet with a race known as the Tuffles. The Saiyans lived in the arid wastelands, while the Tuffles lived in great cities, employing advanced technology. One day however, the Saiyans attacked, vowing to conquer the Tuffle's great cities, and to extinguish the race. This sparked a ten year long war (described in greater detail below).
It is revealed in Plan to Eradicate the Saiyans that when the Saiyans arrived on Planet Plant, they were welcomed by the Tuffles. The Tuffle survivor, Dr.Rachi, then describes the horrors of the war in a similar fashion to the one King Kai tells. However whilst explaining, Vegeta states the Tuffles used the Saiyan race as slaves.