Yuki–Wappo languages
Wappo and Yuki are quite divergent grammatically and lexically (Goddard 1996: 83), which has led to contested theories about their relationship.Yuki is associated with the Mendocino Complex around Clear Lake (3000 BCE), while Wappo of the Napa Valley is associated with the St. Helena Aspect of the Augustine Pattern.The relationship between Yuki and Wappo was contested by Jesse Sawyer who believes that the similarities are due to linguistic borrowing and shared areal features.[2] However, William Elmendorf has presented some persuasive evidence in favor of the relationship, noting that they are as close as two branches of Indo-European.Mithun (1999) reports that the relationship remains open to question, Golla (2011) that it is securely demonstrated.