Nothing contradicts the view that excellent sailing rafts and sewn boats existed in the Indo-Malaysian Archipelago long before the Austronesian ancestors are thought to have moved out of Taiwan. The earliest edge-ground axe-like stone tools that could have made a crude dug-out canoe date from more than 20,000 years ago in Australia and 30,000 years ago in Japan. Humans were obliged to cross the sea to reach Australia, perhaps at first on bamboo rafts and later in dug-out canoes. Bamboo rafts are traditional over much of Indonesia and Melanesia as far as Fiji. Other lightweight timbers for rafts, such as Erythrina which is still used for outrigger floats, are available on the shoreline. Most of the boatbuilding timbers are also extremely widespread and must have been spread by humans, for only some species have seeds that are viable after floating in sea-water. Also, boat technology and agriculture are interconnected because the production of domestic hybrids depends on transporting parent stocks which would otherwise not be brought together.