"According to Renfrew, there are many pitfalls in the attempt to create an “inventory’’ of Proto-Indo-European words. For example, it can be very difficult to determine whether a word truly is inherited from the Proto-Indo-European vocabulary or has been borrowed later from an Indo-European sib­ling language. If this question cannot be resolved, it is impossible to determine whether the object or phenomenon that the word denoted existed in the Proto-Indo-European homeland or is something that people became acquainted with later. And how can we know, Renfrew continues his critical review, that the semantic meaning of a word has been constant over the centuries? Without knowing that, one cannot use the word in question to create a picture of, say, the fauna that the Proto-Indo-Europeans were familiar with."