with the Mature Harappan cities. Bet Dwarka was fortified and continued to have contacts with the Persian Gulf region, but there was a general decrease of long-distance trade. On the other hand, the period also saw a diversification of the agricultural base, with a diversity of crops and the advent of double-cropping, as well as a shift of rural settlement towards the east and the south. The pottery of the Late Harappan period is described as "showing some continuity with mature Harappan pottery traditions," but also distinctive differences. Many sites continued to be occupied for some centuries, although their urban features declined and disappeared. Formerly typical artifacts such as stone weights and female figurines became rare. There are some circular stamp seals with geometric designs, but lacking the Indus script which characterised the mature phase of the civilisation. Script is rare and confined to potsherd inscriptions. There was also a decline in long-distance trade, although the local cultures show new innovations in faience and glass making, and carving of stone beads. Urban amenities such as drains and the public bath were no longer maintained, and newer buildings were "poorly constructed". Stone sculptures were deliberately vandalised, valuables were sometimes concealed in hoards, suggesting unrest, and the corpses of animals and even humans were left unburied in the streets and in abandoned buildings. During the later half of the 2nd millennium BCE, most of the post-urban Late Harappan settlements were abandoned altogether. Subsequent material culture was typically characterised by temporary occupation, "the campsites of a population which was nomadic and mainly pastoralist" and which used "crude handmade pottery". However, there is greater continuity and overlap between Late Harappan and subsequent cultural phases at sites in Punjab, Haryana, and western Uttar Pradesh, primarily small rural settlements. Aryan migration In 1953 Sir Mortimer Wheeler proposed that the invasion of an Indo-European tribe from Central Asia, the "Aryans", caused the decline of the Indus civilisation. As evidence, he cited a group of 37 skeletons found in various parts of Mohenjo-daro, and passages in the Vedas referring to battles and forts. However, scholars soon started to reject Wheeler's theory, since the skeletons belonged to a period after the city's abandonment and none were found near the citadel. Subsequent examinations of the skeletons by Kenneth Kennedy in 1994 showed that the marks on the skulls were caused by erosion, and not by violence. In the Cemetery H