The fully revised fifth edition of this highly acclaimed undergraduate textbook provides a thought-provoking introduction to evolutionary psychology, while assuming no prior knowledge of evolutionary theory. The authors continue to carefully guide students towards a level of understanding where they can critically apply evolutionary theory to psychological explanation, providing an engaging and balanced discussion of the field. New material has been added on female homosexuality, artificial intelligence and language, cooking and human brain expansion, Covid-19 and rates of evolutionary change, and the effects of digital media on mental health. This edition also has new and revised boxed case studies, many new figures, extra discussion questions, and additional further reading suggestions. The text is accompanied by online resources including an updated test bank and lecture slides, as well as new answers to the end-of-chapter questions. This is essential reading for students taking undergraduate and graduate courses in evolutionary psychology.

Polygamy is a form of “one-sided” consensually non-monogamous relationship where one person has multiple committed partners, each of whom is only involved with that one person. It was likely a reoccurring feature of ancestral mating that posed adaptive problems for our ancestors. Yet polygamy, and multi-partnering more generally, is understudied in Western cultures, raising questions about the existence of polygamous interest and whether this is calibrated adaptively to personal conditions. In two studies, we examined polygamous interest in two heterosexual online samples from the UK. In Study 1 ( N = 393), modest interest was found for polygamous relationships overall. Men were six times more open to polygyny than women, but there was little sex difference in openness to polyandry. Further analysis revealed that all forms of multi-partnering were undesirable relative to singlehood and monogamy; however, consensual multi-partner relationships were less undesirable than non-consensual ones. Sex differences were largest for polygyny and arrangements where men had agreed access to a casual partner alongside a committed one, yet these were two of the most acceptable forms of multi-partnering when men and women’s responses were combined. Sociosexuality positively predicted interest in most forms of multi-partnering. Study 2 ( N = 735) focused on polygyny and added status-linked traits as predictors. The results of Study 1 were broadly replicated, though the status-linked traits did not predict polygynous interest specifically. Instead, sociosexuality and male intrasexual competitiveness uniquely predicted general interest in multi-partner relationships. Overall, interest in polygamy appears to emerge despite social discouragement and sex differences in interest track the relative costs and benefits associated with it. However, there is no strong evidence that polygamous interest is uniquely calibrated to personal conditions when compared to other forms of multi-partnering.