It is commonly thought that animals can be arranged along a ladder of intelligence—a sort of modern-day Scala Naturae—with humans inevitably at the top, followed by our close relatives, the primates, all the way down to fish and other slimy creatures. Over the past decade, this ladder has been challenged by claims of high intelligence and great social complexity in other animals. For example, spotted hyenas establish hierarchies in which dominant females support the rank contests of their daughters. Bottlenose dolphins form "political" coalitions every bit as complex as those of chimpanzees. Caledonian crows not only use tools in the wild, but also modify tools in the lab, an ability once thought to define humans.