They are considered to be Algonquians. And though a few disagree, the yuki indians are most likely descended from the Anishinabek (are Anishinabe and also partially other Indian) who commenced the first westward diaspora about 1,000 years ago. They eventually reached the northern California coast, then settled down to live there, primarily near the north central California region, north of San Francisco and on eastward. For 100s of years they lived a quite and possibly even a peaceful life (since they invaded we have good reasons to suspect they had serious problems with the native tribes of that region of California) in north central and northern California.
In the 18th century, the whites (the Spanish) forced their way into California and established numerous missions from San Diego to near San Francisco. They brought along with them their diseases which eventually decimated the Indian population of California, including the Yuki Indian population. However, the Yuki Tribe was not greatly affected by the Spanish missions and many continued to live their ancient traditional way of life. Exactly how many Yuki were murdered by the disease epidemics is not correctly known, but the number most have been large. The Spanish would not keep the California region to themselves. Though the region from San Francisco to San Diego, was inhabited by non Algonquian Indians, just east of where Los Angeles and San Diego are located, scores of Anishinabe soldiers from Arizona, Nevada, New Mexico, and Utah commenced to war upon the white (Spanish) invaders, after the whites commenced to establish the missions there and along the Colorado River, between Arizona and California. Spanish leaders soon requested from other white peoples (the Dutch, English, French and others) to settle down in California, after the commenced to colonize California in 1769.
In the early 19th century, unrest was occurring in Mexico, which eventually led to an Indian Rebellion against Spanish rule. By 1820, Mexico (it was really the Anishinabek and their allies) had overthrown Spanish rule and assumed control over parts of California. At that time California still had 100,000s of Indians, but we must remember that before the white Spaniards invaded, the California Indian population was likely in the millions. In 1820, the Yuki likely numbered in the 10,000s if not over 100,000, but that would change after the English whites brought California under their control after the Mexican-American War ended. After Mexico ceded California to the English, it did not take the whites long to became infatuated over California.
After gold was discovered in California, an instant white immigrant rush to California commenced. Within 10 years the white population of California grew from a couple of thousand in 1848, to several hundred thousand by 1858. By that time the whites had invented the revolver and they put the new weapon to use against the native California Indians, especially against the Yuki people and other Anishinabek. The whites may have murdered 10,000s of the Yuki (that includes by using plague warfare), who did not have equal weapons.The whites likely murdered 100,000s of Indians in California, between 1850 and 1870. It was an act of genocide. The Yuki did not escape from the genocidal act. In fact, the Yuki were the tribe hardest hit by the genocide. That means they were very, very numerous. Just before the United States brought California under white control, those whites who had visited Calfornia made it clear to American leaders that California would be easily stolen and the native Indians would be murdered in the 100,000s because they were still using the lance (spear), bows and arrows, and thus. The Yuki joined with other north central and northern California Indian Tribes, to fight the whites between 1860 and 1870, but they were powerless (they used their primitive weapons) against the superior weapons of the whites. After the northern California Indian Wars stopped, the Yuki Tribe signed a treaty with the United States, in which they ceded their lands, and were granted a reservation in California.