Wallace Arthur is Emeritus Professor of Zoology at the National University of Ireland, Galway. He is one of the founders of the interdisciplinary field of evolutionary developmental biology (evo-devo), and has a special interest in explaining scientific concepts in plain, nontechnical language. He is the author of nine previous books, including Biased Embryos and Evolution (Cambridge, 2004) and The Origin of Animal Body Plans (Cambridge, 1997).