At the time of the first European contact, Native American tribes in California included the Chumash, Nisenan, Maidu, Miwok, Modoc, Mohave, Ohlone, Pomo, Serrano, Shasta, Tataviam, Tongva, Wintu, Yurok, and Yokut. The relative strength of the tribes was dynamic, as the more successful expanded their territories and less successful tribes contracted. Slave-trading and war among tribes alternated with periods of relative peace. The total population of Native California is estimated, by the time of extensive European contact in the 18th century, to have been perhaps 300,000. Before Europeans landed in North America, about one-third of all natives in what is now the United States were living in the area that is now California. California indigenous language diversity numbered 80 to 90 languages and dialects, some surviving to the present although endangered.