economic organisation. New coastal societies emerged around tidal reefs, estuaries and flooded river valleys, and coastal islands were incorporated into local economies. There was a proliferation of stone tool, plant processing and landscape modification technologies. Elaborate fish and eel traps involving channels up to three kilometres long were in use in western Victoria from about 6,500 years ago. Semi-permanent collections of wooden huts on mounds also appeared in western Victoria, associated with a more systematic exploitation of new food sources in the wetlands. Aboriginal Tasmanians were isolated from the mainland from about 14,000 years ago. As a result, they only possessed one quarter of the tools and equipment of the adjacent mainland and were without hafted axes, grinding technology, stone tipped weapons, spear throwers and the boomerang. By 3,700 BP they had ceased to eat fish and use bone tools. Coastal Tasmanians switched from fish to abalone and crayfish and more Tasmanians moved to the interior. The Tasmanians built watercraft from reeds and bark and journeyed up to 10 kilometres offshore to visit islands and hunt for seals and muttonbirds. Around 4,000 years ago the first phase of occupation of the Torres Strait Islands began. By 2,500 years ago more of the islands were occupied and a distinctive Torres Strait Island maritime culture emerged. Agriculture also developed on some islands and by 700 years ago villages appeared. One genetic study in 2012 has suggested that about 4,000 years ago, some Indian explorers settled in Australia and assimilated into the local population. However, more recent studies do not support this view. Nevertheless, some innovations were imported to the mainland from neighbouring cultures. The dingo was introduced about 4,000 years ago. Shell fish hooks appeared in Australia about 1,200 years ago and were probably introduced from the Torres Strait or by Polynesian seafarers. From the mid-1660s fishing vessels from Indonesia regularly visited the north coast of Australia in search of trepang (sea cucumber). Trade and social relationships developed which were reflected in Aboriginal art, ceremonies and oral traditions. Aboriginal people adopted dugout canoes and metal harpoon heads from the Indonesians which allowed them to better hunt dugong and turtle off the coast and nearby islands. Despite these interactions with neighbouring cultures, the basic structure of Aboriginal society was unchanged. Family groups were joined in bands and clans averaging about 25 people, each with a defined territory for foraging. Clans were attached to