Thanks to a Godfrey Hewitt Mobility Award from ESEB, Ben Hopkins is undergoing a two-week state change from empiricist to modeller. His on-going DPhil work at the University of Oxford is concerned with the antagonistic side of sex in the fruit fly Drosophila melanogaster, where intrasexual male competition can favour the evolution of seminal fluid components that harm females. During his short time with the Kokkonuts, he will be considering the opposite end of the social behaviour spectrum by asking ‘under what conditions is actively caring for one’s partner advantageous?’