Orcas (or killer whales) are one of the planet's supreme predators. Alongside humans, they have the most complex brains to be found in nature. But while one of these two species has killed 200 million members of its own kind in the twentieth century alone, the other has killed none. This is where Beasts begins: there is something different about humans. Masson has shown us that animals can teach us much about our own emotions - about love (dogs), contentment (cats) and grief (elephants). But they have much to teach us about the negative emotions such as anger and aggression as well, and in unexpected ways. In Beasts he demonstrates that the violence we perceive in the 'wild' is mostly a matter of projection. We link the basest human behaviour to animals, to 'beasts', and claim the high ground for our species. We are least 'human', we think, when we succumb to our primitive, animal instincts. In fact, nothing could be further from the truth. Animal predators kill to survive, but there is nothing in the annals of animal aggression remotely equivalent to the violence mankind has inflicted upon itself. Humans, and humans in our modern industrialised world in particular, are the most violent species in existence. We lack what all other animals have: a check on aggression that serves the species rather than destroys it. And it is here that animals have something vitally important to teach us about ourselves.