 In general, the issue of the nature of proto-language remains unresolved, with linguists generally taking either the "realist" or "abstractionist" position.Even the widely studied proto-languages, such as Proto-Indo-European, have drawn criticism for being outliers typologically with respect to the reconstructed phonemic inventory.The alternatives such as glottalic theory, despite representing a typologically less rare system, have not gained wider acceptance, with some researchers even suggesting the use of indexes to represent the disputed series of plosives.