The first boomerang was found in Poland, not Australia
"The oldest Australian Aboriginal boomerangs are ten thousand years old... One boomerang that was discovered in Jaskinia Obłazowa in the Carpathian Mountains in Poland was made of mammoth's tusk and is believed, based on AMS dating of objects found with it, to be about 30,000 years old."
http://www.buzzfeed.com/daves4/20-things-you-never-knew-about-popular-inventions