The author details her team’s research investigating sex differences in serial murder from an evolutionary perspective. Per Trivers’ (1972) Parental Investment Theory, evolved psychological mechanisms serve sex-specific interests to maximize reproductive fitness (genes represented in subsequent generations). As predicted, men – who produce millions of sperm daily and have an increased sex drive – commit serial murder primarily for sexual reasons. Women, who have limited reproductive opportunities compared to men, have evolved to place great importance on resources. As such, women commit serial murder primarily for monetary gain. Moreover, mirroring ancestral agrarian tendencies, male serial killers (MSKs) are hunters (stalkers) of victims, and female serial killers (FSKs) are gatherers of profit and “gather” victims in their immediate environment, including relatives. The author stresses that an evolutionary perspective (ultimate perspective) does not explain the entirety of serial murder. We must consider converging perspectives, including evolutionary, proximate biological, clinical, traumagenic, cultural, historical, social, and gender-role forces that contribute to the development and growth of the human psyche.