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This article reviews some recent evolutionary psychological theories about the interaction between environmental factors and sexual strategies. Evolutionary psychology explains sexual strategies in terms of innate information-processing mechanisms. The most important theoretical instrument relating to this topic is the theory of sexual selection and parental investment. Because of the unequal parental investment of the sexes, their sexual strategies differ. This is an important source of conflict between the sexes. Humans evolved in a complex social environment. As a consequence, human psychic mechanisms produce a wide variety of sexual strategies. Two dimensions along which human sexual strategies vary are considered here. First, people's mating strategies range from striving for a lifelong pair bond to aiming at a single act of copulation with someone. Second, strategies situated at the long-term end of the continuum can be polygynous, monogamous or polyandrous. The choices made by a concrete individual are influenced by several factors such as the personal life history, the general availability and predictability of resources, the distribution of political and economic power between men and women, the distribution of political and economic power between men themselves, the production mode of a society and finally the content of cultural representations in a society. It is shown that evolutionary psychology can be important for the explanation of contemporary behavioural differences. Some methodological problems of evolutionary psychology are reviewed and an evolutionary psychological perspective on the sex/gender distinction is considered.

In this article, I advance a novel hypothesis on the evolution of hominin bipedalism. I begin by arguing extensively for how the transition to bipedalism must have been problematic for hominins during the Neogene. Due to this and the fact that no other primate has made the unusual switch to bipedalism, it seems likely that the selection pressure towards bipedalism was unusually strong. With this in mind, I briefly lay out some of the most promising hypotheses on the evolutionary origin of hominin bipedalism and show how most, if not all, fail in the face of the need for an unusually strong selection pressure. For example, some hypotheses maintain that hominins became bipedal so they could use their hands for carrying infants, food, or other valuable objects. But extant apes are able to carry objects in one of their front limbs (while walking with the other three), and thus it does not seem plausible that our hominin ancestors went through the troublesome transition to bipedalism just so they could carry objects a little more efficiently. After I show that past hypotheses are wanting in the face of this challenge, I argue that there is only one selection pressure powerful enough to instigate a strange and problematic evolutionary adaptation like bipedalism, and that is sexual selection. Specifically, from the fact that bipedal locomotion is an important strategy for intimidating others and ascending the dominance hierarchy in extant apes, I argue that for no particular selective reason bipedal locomotion became a signal for high fitness (much as a large and intricate tail became a signal for high fitness for peahens), and this led to the trait being continuously reinforced in spite of all its deleterious fitness consequences.

Courters' conformity to the "mass standard", represented by the courtship ritual of each species, behaviorally confirms their possession of their species' standard genetic programming, thus validating their qualification jar reproductive privilege. The standard
of each species is thereby affirmed and reinforced and the reproductive worthiness of individuals thereby tested. In this lies the only "universal" element of significance to courtship rituals. Not only do the rituals (which constitute communicational codes of symbolic behavioral
"passwords" between conspecifics) serve to verify the "authenticitynormality" of both courter and courted, but, accordingly, the rituals' very behavioral statement is a necessary, validating "key" to the release of further, ultimate mating activity.

This paper proposes an explanation for the universal human desire for increasing consumption and the associated propensity to trade survival opportunity off conspicuous consumption. I argue that this desire was moulded in evolutionary times by a mechanism known to biologists as sexual selection, whereby an observable trait — conspicuous consumption in this case — is used by members of one sex to signal their unobservable characteristics valuable to members of the opposite sex. It then shows that the standard economics problem of utility maximisation is formally equivalent to the standard biology problem of the maximisation of individual fitness, the ability to pass genes to future generations, and thus establishes a rigorous theoretical foundation for including conspicuous consumption in the utility function.

In a recent issue of this journal, Vandermassen suggested that feminists should include sexual selection theory and evolutionary psychology in a unifying theory of human nature. In response, this article aims to offer some insight into the development of sexual selection theory, to caution against Vandermassen's unreserved assimilation and to promote the opposite ongoing integration — an inclusion of gender perspectives into evolutionary biology. In society today, opinions about maintaining traditional sex roles are often put forward on the basis of what is natural and how animals behave. However, the natural sciences have proved to be pervaded by gendered values and interests; Darwin's theory of sexual selection has been criticized for being male biased, and partly due to the unwillingness of Darwin's scientific contemporaries to accept female choice, research has been overwhelmingly focused on males. More recently, theory has become less gender biased and research has come to include a large variety of issues not present in the first version of the theory. However, there is a need to increase the awareness of gender bias in order to develop a gender-neutral evolutionary biology.

Today the modern Darwinian theory of evolution is the unifying theory within the biological sciences. A consideration of its implications for feminism is, however, impossible without a critical evaluation of its history of male bias. The aim of this article is therefore threefold. First, to explain what sexual selection entails. Second, to discuss male bias in and feminist reactions to Darwinian theory in general and sexual selection theory in particular. Third, to demonstrate that it would be a loss for feminism to keep rejecting an evolutionary framework if we want to understand the roots of gender difference. This article is informed by a Darwinian feminist perspective.

In a recent issue of this journal, Vandermassen suggested that feminists should include sexual selection theory and evolutionary psychology in a unifying theory of human nature. In response, this article aims to offer some insight into the development of sexual selection theory, to caution against Vandermassen's unreserved assimilation and to promote the opposite ongoing integration — an inclusion of gender perspectives into evolutionary biology. In society today, opinions about maintaining traditional sex roles are often put forward on the basis of what is natural and how animals behave. However, the natural sciences have proved to be pervaded by gendered values and interests; Darwin's theory of sexual selection has been criticized for being male biased, and partly due to the unwillingness of Darwin's scientific contemporaries to accept female choice, research has been overwhelmingly focused on males. More recently, theory has become less gender biased and research has come to include a large variety of issues not present in the first version of the theory. However, there is a need to increase the awareness of gender bias in order to develop a gender-neutral evolutionary biology.

Theoretical and empirical studies have shown that species radiations are facilitated when a trait under divergent natural selection is also involved in sexual selection. It is yet unclear how quick and effective radiations are where assortative mating is unrelated to the ecological environment and primarily results from sexual selection. We address this question using sympatric grasshopper species of the genus Chorthippus, which have evolved strong behavioural isolation while lacking noticeable ecomorphological divergence. Mitochondrial genomes suggest that the radiation is relatively recent, dating to the mid-Pleistocene, which leads to extensive incomplete lineage sorting throughout the mitochondrial and nuclear genomes. Nuclear data shows that hybrids are absent in sympatric localities but that all species have experienced gene flow, confirming that reproductive isolation is strong but remains incomplete. Demographic modelling is most consistent with a long period of geographic isolation, followed by secondary contact and extensive introgression. Such initial periods of geographic isolation might facilitate the association between male signaling and female preference, permitting the coexistence of sympatric species that are genetically, morphologically, and ecologically similar, but otherwise behave mostly as good biological species. ; RJP was funded by the European Union's Horizon 2020 research and innovaion programme, under the Marie Sklodowska-Curie grant agreement No. 658706. II was supported by a Juan de la Cierva-Incorporación postdoctoral fellowship (IJCI-2016- 29566) from the Spanish Ministry for Science and Competitiveness (MINECO). Computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at Uppsala Multidisciplinary Centre for Advanced Computational Science (UPPMAX) under Project SNIC 2019/8-67.