Siouan languages
In the 19th century, Robert Latham suggested that the Siouan languages are related to the Caddoan and Iroquoian languages. In 1931, Louis Allen presented the first list of systematic correspondences between a set of 25 lexical items in Siouan and Iroquoian. In the 1960s and 1970s, Wallace Chafe further explored the link between Siouan and Caddoan languages. In the 1990s, Marianne Mithun compared the morphology and syntax of all the three families. At present, this Macro-Siouan hypothesis is not considered proved, and the similarities between the three families may instead be due to their protolanguages having been part of a sprachbund.
East Formosan languages
The East Formosan languages consist of various Formosan languages scattered across Taiwan, including Kavalan, Amis, and the extinct Siraya language. This grouping is supported by both Robert Blust and Paul Jen-kuei Li. Li considers the Siraya-speaking area in the southwestern plains of Taiwan to be the most likely homeland of the East Formosan speakers, where they then spread to the eastern coast of Taiwan and gradually migrated to the area of modern-day Taipei (Li 2004).Li (2004) presents the following criteria as evidence for an East Formosan subgrouping.Li (2004) notes that the split of *k into k and q (before *a) is shared exclusively by Basay and Kavalan. Like Kavalan and Basay, the Siraya language merges the patient-focus and locative-focus forms, although Amis distinguishes the two focus forms. Li (2004) also lists dozens of lexical innovations shared by the East Formosan languages.