Rock soil droplets formed by heating most likely came from Stone Age house fires and not from a disastrous cosmic impact 12,900 years ago, according to new research from the University of California, Davis. The study, of soil from Syria, is the latest to discredit the controversial theory that a cosmic impact triggered the Younger Dryas cold period. The Younger Dryas lasted a thousand years and coincided with the extinction of mammoths and other great beasts and the disappearance of the Paleo-Indian Clovis people. In the 1980s, some researchers put forward the idea that the cool period, which fell between...