We share so much of our genetic material with other apes and it is clear that, like other species alive on earth today, we have evolved by the Darwinian process of natural selection. We can therefore learn about our own sexuality by looking at how sex works in other species. Gribbin and Cherfas put forward the challenging theory that males have outlived their evolutionary usefulness and include discussion of ideas such as the red queen effect (the need to run as fast as possible, in evolutionary terms, in order to stay in the same place) and the growing resistance bacteria have evolved to widely used drugs.