Using the majority principle, we can suggest that the older forms will most likely based on language 2 or language 3.lf this  correct,then the consonant changes must have been [p]_[b],[t]_[d] and [K]_[g] in order to produce the later froms in language 1.there is a pattern these changes that follows one part of the'most natural development principle`i.e voiceless sounds become voiecd between vowels. So the words in. Language 2 and 3 most be older from than those in language 1. 
which of the two lists 2or 3,contains the older forms? Remembering one other' most natural development` type of sound change ( i.e final vowles  often disappear),we can propose that the words in language 3 have consistently lost the final vowles still present in the words of language 2. Our best guess, then, is that the. forms listed for language 2 are closet to what most have been the original proto-fomrs