The great objection which he cites to the northern passage is the existence of the barren Ust Urt desert. Also the fact that the Caspian has steadily been becoming more shallow and contracting in area. These two points, if true, to some extent contradict one another. It is true, doubtless, that at one time the Caspian had covered a greatly extended area, but it is not so clear that its contraction has been a steady progress. We have already seen, from the evidence cited by Ellsworth Huntington,[457] that this contraction and expansion has probably been intermittent. In any case, the contraction has been due to light rainfall, and it is this light rainfall which has produced the desert condition of the Ust Urt. When the Caspian expanded, it was because of increased precipitation, when such parts of the Ust Urt as were not inundated would have been a grassy steppe. Dr. Giles suggests that at one time the Caspian and Aral seas were one great inland sea, and that such was at one time the case is implied by extracts from the writings of Herodotus.[458] But though this was almost certainly the case during periods of relatively heavy rainfall, the level would have to have risen well above the 200 metre contour to have obstructed the passage between the Russian and Turkestan steppes. Such a rise is quite unthinkable during the last 6000 years, for had the surface been raised 220 feet above the present sea level the Caspio-Aral Sea would have been connected with the Euxine.[459] Even had the impossible occurred and the 200 metre contour been reached it would have been quite easy to pass from one steppe area to another, by crossing the southern slopes of the Urals, which are raised very little above the plain and would form no obstacle to nomad tribes. The Anatolian passage was by no means an easy route to the east, for had the Wiros kept to the north they would have found difficulty in crossing the Armenian mountains; further south they would have come into contact with the peoples of Mesopotamia, and we should have found evidence of their presence. That some of them passed this way about 2200 /B.C./ we have already seen, but others had passed eastwards earlier, apparently by a different route, for otherwise it is difficult to account for the presence of the Kassites on the Iranian plateau in the time of Hammurabi. The complete absence of any evidence of a movement eastward from the Hungarian plain in neolithic days, and the fact that any such movement would have been compelled to cross the area occupied by the settled Tripolje-folk, seem to be fatal to the literal acceptance of this hypothesis.