There are more stems per item in Athabascan, which expresses the fact that the Athabascan languages have undergone somewhat more change in diverging from proto Athabascan than the Yokuts languages from proto Yokuts. This may be because the Athabascan divergence began earlier; or again because the Athabascan languages spread over a very much larger territory (including three wholly separated areas); or both. The differentiation however is not very much greater, as shown by the fact that Athabascan shows 3.46 stems per meaning slot as against 2.75 for Yokuts, with a slightly greater number of languages represented in our sample: 24 as against 21. (On deduction of one-eighth from 3.46, the stem/item rate becomes 3.03 against 2.75 in equivalent number of languages.) These general facts are mentioned to make clear that the total situation in the two families is similar enough to warrant comparison.

The greatest difference in the two sets of figures is due to differences in the two sets of lists used. These differences in turn result from the fact that my Yokuts vocabularies were built up of terms selected mainly to insure unambiguity of English meaning between illiterate informants and myself, within a compact and uniform territorial area, but that Hoijer's vocabulary is based on Swadesh's second glottochronological list which aims at eliminating all items which might be culturally or geographically determined. Swadesh in short was trying to develop a basic list that was universal; I, one that was specifically adapted to the San Joaquin Valley. The result is that I included 70 animal names, but Swadesh only 4; and somewhat similarly for plants, 16 as against 4. Swadesh, and therefore Hoijer, felt compelled to omit all terms denoting species or even genera (fox, vulture, salmon, yellow pine, manzanita); their classes of animal and plant terms are restricted to generalizations or recurrent parts (fish, bird, tree, grass, horn, tail, bark, root). The groups are therefore really non comparable in content as well as in size.