How do linguists determine whether Afro-Asiatic languages are genetically related?

Linguists determine whether languages are genetically related by applying the comparative method, which involves the systematic analysis of phonologies, vocabularies, and grammars. To establish a genetic relationship, languages must demonstrate matches that can be systematically traced to a common protolanguage and are not the result of chance or previous contact between unrelated groups.1

Applying these methods to the Afro-Asiatic phylum is complex due to several factors:

• Lack of Written Records: Most Afro-Asiatic languages are living languages without historical documents, making it difficult to track changes over time.1
• Semitic Bias: Because the Semitic family is relatively homogeneous and well-documented, some scholars have incorrectly assumed that the ancestral Proto-Afro-Asiatic language resembled a "Semitic type," a theory not supported by data from other African branches.1
• Vowel Omission: Many Afro-Asiatic writing systems do not indicate vowels, complicating the reconstruction of vocabulary and grammar.1
• Remote Kinship: The degree of relationship between the six major divisions—Amazigh, Chadic, Cushitic, Egyptian, Omotic, and Semitic—is considered very remote, and there is no final consensus on their exact subclassification.2