AUSTRALIA: Native Australians first arrived on the island continent more than 40,000 years ago. It has been widely believed that they were isolated, culturally and genetically, from the rest of the world prior to European contact in the 17th century. But there was always the question of who brought the dingo, which was introduced around 4,000 years ago. A new genetic analysis shows that there was actually substantial gene flow between India and Australia around this time, which also coincides with changes in tools and food-processing technology. —Samir S. Patel