Divisions of labor are common among many species. They occur when some sets of individuals (usually defined by age or gender) regularly perform specific tasks, either as a result of individual decision-making patterned by social and ecological contexts (differences in labor), or emerging from an organized, cooperative task specialization designed to benefit a larger collective (divisions of labor). This chapter explores both differences in labor and divisions of labor by drawing on ethnographic cases of subsistence production. These case studies illustrate how intrinsic variation in size and strength may structure differences in labor by age, and they demonstrate how variation in the assessment of acquisition risk may influence women’s and men’s subsistence decisions. These differences may lead to true cooperative divisions of labor when team rates, bargaining, or signaling reduce conflicts of interest between individuals, in turn facilitating increased returns to scale for larger collectives, families, households, or other unit of economic production. Understanding the maintenance of patterns in "divisions of" and "differences in" labor provides a firmer foundation for explanatory models of human decision-making, ranging from questions about the emergence of our genus to contemporary patterning in occupational specialization and gender identity.

Humans are complexly social and exceptionally cooperative. Human behavioral ecology has been successful by explaining small-scale dyadic cooperative interactions like food sharing using standard theoretical perspectives of kin selection and reciprocity. Such models have been enhanced with additional ideas including mutualism, partner choice, costly signaling, competitive altruism, and biological market theory. Concepts such as stake, interdependence, and need-based support have provided additional predictive power. While these tools have been effective at explaining face-to-face cooperative relationships, their inability to explain the large, complex social groupings typical of human societies has led researchers to look to new models of multilevel and cultural group selection theory for solutions. Culture plays a key role in structuring human sociality and facilitating group selection by reducing behavioral variation within groups while increasing variation among groups. Gene-culture coevolution can favor psychological propensities like conformist bias that assort people into symbolically marked groups of trusted partners with shared identities and normative ways of organizing cooperative life. Societies whose cumulative culture maintain institutions that encourage magnanimity and coordination between members achieve collective action benefits unobtainable otherwise and outcompete other groups whose institutions fail to organize their members in ways that lead to cooperative outcomes at scale.

The problem with cheap talk communication is that it is free to lie in an effort to obtain a better outcome. What if signals were costly instead? This chapter investigates that question from the perspective of military mobilizations. We see that such mobilizations can credibly communicate a state’s resolve because less resolved types pay differential costs to mobilize. Unfortunately, this means that mobilizations are not as useful for revealing private information about the costs of war or a state’s martial effectiveness.

This chapter explores interpersonal attraction, the subjective appeal of another person, which is often accompanied by a positive emotional reaction and an affiliative motivation for greater closeness to that person. This chapter organizes the many specific traits that enhance attraction in terms of characteristics that offer domain-general rewards (e.g., pleasure, self-esteem, belonging) and characteristics that advance specific evolutionary goals (e.g., survival, reproduction). The chapter then reviews the characteristics that are most consistently desirable, including physical attractiveness, social status, warmth/kindness, intelligence, proximity, familiarity, similarity, and reciprocity by reviewing relevant research findings, as well as exceptions and boundary conditions. The chapter ends with a review of how sociocultural factors, including the immediate situation, women’s reproductive cycles, and the broader relationship trajectories provide context for understanding romantic attraction.

Evolutionary psychologists have long maintained that humans’ moral sense is essential to their success as a species and part of what makes humans unique among animals. Moral systems have functional roots, helping individual organisms survive, thrive, and pass on their genetic material. It is not despite anarchy but because of anarchy that humans have an ethical sense. Evolutionary theorists identify moral condemnation and binding morality as crucial for the emergence of other-regarding, altruistic behavior that makes liberal morality possible in the first place. When others harm us, or even third parties, we condemn, passing moral judgments and sometimes retaliating; we do not speak evil but speak of evil. Moral condemnation encouraged the development of moral conscience to avoid the outrage of, and often violent group punishment by, those who were wronged. This internalized sense of right and wrong in turn acted as a credible signal of cooperativeness that unwittingly and unconsciously paid material dividends. Group favoritism, also thought to have evolutionary origins, is moral in nature as well. Those early humans who felt obligated to contribute to the collective defense against common threats in an extremely dangerous environment could prosper enough to offset the competing incentives to free-ride within the group.

Relative to other species, human females invest considerable effort in attracting and retaining mates. Stroll the aisles of any bookstore and you may come across titles such as “Get the guy: Learn secrets of the male mind to find the man you want and the love you deserve” (Hussey, 2014), and “Texts so good he can't ignore: Sassy texting secrets for attracting high-quality men” (Bryans, 2018). A desire to attract and retain mates underlies diverse facets of women’s psychology and behavior, including displaying or enhancing aspects of one’s personality and physical appearance. Not surprisingly, these efforts correspond with men’s mate preferences. Human males are unique in their relative choosiness surrounding their mates, especially within the context of long-term pair-bonding. Look further in that bookstore aisle and you might come across a title such as “The man's handbook for choosing the right woman” (Daniels, 2009). In this chapter, we examine the theoretical rationale underlying female intersexual selection. We begin with a discussion of the theory underlying human mate choice, highlighting why men’s choosiness has been selected for, and why this compels women to exert effort toward attracting men. We then discuss specific characteristics of men’s short-term and long-term mate choice, and the multitude of tactics women utilize to better embody those traits. We describe preliminary evidence surrounding how intersexual selection may have shaped some phenotypic traits in women as costly signals of underlying fertility or immunocompetence. Finally, we discuss both individual and contextual differences among women in their mating effort and provide suggestions for future research directions aimed at further understanding how intersexual selection has shaped women’s mating psychology.

This chapter analyzes Turkey’s rapprochement with Russia, particularly in security and defense. It analyzes two case studies: Turkey’s declared intent of becoming a member of the Shanghai Cooperation Organization (SCO) and the agreement signed with Russia to buy a missile defense system. It argues that Turkey’s intention to become an SCO member may be labeled as a compellent threat for alternative alliances against the West. Hence, it represents boundary challenging. Furthermore, by signing an agreement to purchase an S-400 missile defense system, Turkey signals to the West that the NATO defense shield system is not the only alternative and engages in collaborative balancing with Russia on defense. Representing boundary breaking against the West, as an S-400 missile defense system would not only be incompatible with the defense network of NATO but also risk intelligence infiltration into NATO’s networks. Turkey signals its resolve to engage in cooperative balancing with Russia, as it does not give in to the threats that its potential F-35 deal with the USA would be jeopardized, uses blackmail power, and makes compellent threats, which indicate a switch to boundary breaking.