California condor embryos can develop without fertilisation Shutterstock/Barbara Ash On the Origin of Sex Lixing Sun, Profile Books As children, many of us learn the facts of life with examples from the natural world. The thinking is that it is more straightforward (and certainly less uncomfortable) to illustrate “the talk” with images of birds laying eggs and bees pollinating flowers than it is to focus on humans or, heaven forbid, your parents. But this is a comforting fiction, as evolutionary and behavioural biologist Lixing Sun sets out in his engaging and frequently mind-boggling book, On the Origin of Sex: The weird and wonderful science of how our planet is populated . The “birds and the bees” analogy just doesn’t capture the diversity, drama and strangeness of animal reproduction.…