Additionally, apparent cognates can arise by chance or from loan words.The branches of Eurasiatic vary between proposals, but typically include Altaic (in the form of Mongolic, Tungusic and Turkic), Chukchi-Kamchatkan, Eskimo–Aleut, Indo-European, and Uralic—although Greenberg uses the controversial Uralic-Yukaghir classification instead.Other branches sometimes included are the Kartvelian and Dravidian families, as proposed by Pagel et al., in addition to the language isolates Nivkh, Etruscan and Greenberg's "Korean-Japanese-Ainu." Some proposals group Eurasiatic with even larger macrofamilies, such as Nostratic; again, many other professional linguists regard the methods used as invalid.Eurasiatic is a proposed language macrofamily that would include many language families historically spoken in northern, western, and southern Eurasia.
According to Ruhlen, this pattern is not found in language families or languages outside Eurasiatic.
In 2000, he expanded his argument for Eurasiatic into a full-length book, Indo-European and Its Closest Relatives: The Eurasiatic Language Family, in which he outlines both phonetic and grammatical evidence that he feel demonstrates the validity of language family.
The heart of his argument is 72 morphological features that he judges as common across the various language families he examines.
Greenberg's Eurasiatic hypothesis has been dismissed by many linguists, often on the ground that his research on mass comparison is unreliable.
Joseph Greenberg's proposal, dating to the 1990s, is the most widely discussed version.
In 2013, Mark Pagel and three colleagues published what they believe to be statistical evidence for a Eurasiatic language family.