A Mission Record of the California Indians, by A.L. Kroeber, , at sacred-texts.com
They say that the first Indians to settle this country came from the north after a great flood; 57 that some went back and did not return; and that here sprung the single common language which is spoken in the seven missions about here, although somewhat changed [from place to place.]
They did not have chiefs. The bravest and strongest were those who went out to their wars. Every man acted as he wished.
24:56 The mission of San Juan Bautista is farthest inland of those in Costanoan territory. The dialect of San Juan Bautista, named Mutsun after a village near the mission, is known from a grammar and phrase-book prepared by Father Felipe Arroyo de la Cuesta, who is probably the author of the following replies, as he was at San Juan Bautista at the time the report was called for.
24:57 That the Indians of this region believed in a great flood or primeval water, is corroborated by such information as there is in existence about their mythology. That they had a tradition of a migration from the north seems more doubtful, not so much because there is any positive information to the contrary, as that the most careful inquiries among nearly all the surviving tribes of central California have failed to reveal the existence of any migration legends or historical traditions. See the introduction to a collection of Indian myths of south central California, published in the fourth volume of the present series.