The glottalized stop—which hardens a consonant—tends to weaken and disappear in most languages of the world.So we surmised that—among the labial stops—it was the "p"'rather than the "b" that most likely had been suppressed in the Indo-European pro t o language .
In the classical system the word is *gwou, which is practically the same as that in Sanskrit.
In accordance with Grimm's law, the transformation of *gwou to the German would require devoicing of the first consonant from "g" to "k." And so the glottalic system seems to make the most sense: it eliminates the need for devoicing and correlates the voiceless stops in the Germanic languages (German, Dutch, Scandinavian and English) with voiceless glottalized stops in the ancestral Indo-European protolanguage.
The Indo-European words for "barley," "wheat" and "flax"; for "apples," "cherries" and their trees, for "mulberries" and their bushes; for "grapes" and their vines; and for the various implements with which to cultivate and harvest them describe a way of life unknown in northern Europe until the third or second millennium B.
C., when the first archaeological evidence appears.
In the scheme we have developed, the corresponding consonants are sounded with a glottalized stop: a closure of the throat at the vocal cords that prevents the outward flow of breath.