Graeme Ruxton has co-written two books, both published by Oxford University Press - 'Living in Groups' (2002) for the Oxford Series in Ecology and Evolution, and the textbook 'Elementary Experimental Design for the Life Sciences' (2003). He is also the author of over 100 scientific articles. His background in physics provides particular strength in the functional aspects of signalling systems discussed in this book. Tom Sherratt is the author of nearly 50 scientific papers on subjects ranging from the evolution of co-operation, to the maintenance of imperfect mimicry and the evolution of