Ancestral Human Societies Research Articles

The Evolutionary Origins of Same-Sex Attraction: Assessing Weak Negative Selection and Positive Selection Arguments

About one in five individuals is not attracted exclusively to members of the opposite sex. The presence of same-sex attraction in such a high frequency constitutes a major evolutionary puzzle. One solution that has been proposed is weak negative selection pressures exercised on deviations from exclusive heterosexual attraction in ancestral human societies. The current paper employs a population genetics model in order to assess the explanatory power of this hypothesis. By investigating different scenarios, it is found that weak selection pressure falls short in accounting for the observed prevalence rates of same-sex attraction. On this basis, it is argued that positive selection is also required. By examining the shape of the distribution of same-sex attraction, it is further argued that positive selection pressure has been exercised on heterosexual orientation with same-sex attraction in women and possibly in men, and on homosexual orientation in men. In addition, it is proposed that male preferences for same-sex attraction are the main source of positive selection of female same-sex attraction. The source(s) of positive selection of male same-sex attraction is, however, obscure.

Why Men Hunt and Women Gather for Recreation? An Evolutionary Perspective

People, predominantly men, spend considerable resources in engaging in hunting animals for sport. Such activity is puzzling, as men take risk and sacrifice valuable resources in killing animals, the meat of which they do not need for their subsistence. Toward solving this puzzle, an evolutionary framework was proposed, where the division of labor in ancestral human societies has resulted in men and women having evolved different mechanisms that motivate them to engage in different activities. On the basis of this framework, two hypotheses were derived. First, on average, men would tend to find hunting an enjoyable activity, while women would tend to find gathering an enjoyable activity. Second, on average, men would be willing to engage in hunting, and women would be willing to engage in gathering. Evidence from two independent studies found strong support for both hypotheses.

The evolution of same-sex attractions: Parental and intimate partners' reactions to deviations from exclusive heterosexual orientation

A considerable portion of the population experiences same-sex attractions. One possible factor that accounts for this phenomenon is that the selection pressures, coming predominantly from parents and intimate partners, exercised on sexual orientation in ancestral human societies had been weak. Based on this evolutionary framework, three hypotheses are derived and tested: First, it is hypothesized that men are less distressed than women by the same-sex attractions of their opposite-sex partners. Second, it is hypothesized that parents are less distressed by the same-sex attractions of their daughters than of their sons. Finally, the hypothesis is tested that the distress of intimate partners and parents over the sexual attractions of their mates and children respectively, is contingent upon the degree of the same-sex attractions: The more these deviate from exclusive heterosexual orientation, the stronger the reactions will be. Evidence from two independent studies finds support for all three hypotheses. These findings are applied in understanding the prevalence of same-sex attractions in contemporary populations.

Size did not matter: An evolutionary account of the variation in penis size and size anxiety

AbstractThe human penis exhibits considerable variation in size, while a substantial proportion of the adult male population experiences size anxiety. This paper employs an evolutionary framework in order to understand this variation, as well as the concern men exhibit about the adequacy of the size of their penis. It is argued that female choice has been one important sexual selection force, responsible for shaping the size of the penis. However, this force has been relatively weak, because women do not consider the size of their partners’ penis to be the most important determinant of their sexual satisfaction. Also, in ancestral human societies, sexual satisfaction was a secondary concern, while women had limited space to exercise mate choice. The mismatch between ancestral and modern conditions, with female choice being stronger in the present than in the past, causes anxiety in men about their ability to satisfy their partners, which is also manifested in their concerns about size.

Sexual selection in ancestral human societies: The importance of the anthropological and historical records.

Application of the sexual selection theory is required for understanding the evolution of the human mind. Still, sexual selection is not a homogenous force, and there are different sexual selection forces. It has been generally assumed that female choice had been the primary sexual selection force during the period of human evolution. More recently, however, it has been proposed that male-male competition and parental choice respectively, had been instead the primary sexual selection forces. This article argues that any theorizing on sexual selection in ancestral human societies needs to be consistent with the anthropological and historical records. Based on this reasoning, it argues further that systematic evidence from these sources is consistent with the hypothesis that male parental choice had been the primary sexual selection force during most of the period of human evolution, while female choice and male-male competi- tion had also been important sexual selection forces. Individuals who are unable to attract and retain members of the opposite sex for the pur- pose of reproduction pay a heavy fitness cost and will be selected out of the population. This translates into sexual selection being a powerful evolutionary force in sexually reproducing spe- cies like our own. Accordingly, the human mind should have been the primary target of sexual selection forces; that is, many behavioral mech- anisms have evolved to enable us to attract and retain members of the opposite sex. In consequence, the application of sexual selec- tion theory becomes central in the evolutionary studies of human behavior. Yet, sexual selection is not a homogenous force as there are distinct sex- ual selection forces. At present, there is a disagree- ment over which sexual selection force has been the primary one in ancestral human societies dur- ing the period of human evolution. In particular, most researchers (e.g., Buss, 2003; Miller, 2000) have assumed that female choice had been the primary sexual selection force. Puts (2010) has argued that male-male competition had been the primary sexual selection force, yet Apostolou (2007, 2010) has argued that it had been parental choice. Given the importance of sexual selection theory for understanding the human mind, this argument needs to be resolved for evolutionary research to be based on solid assumptions about ancestral human condition. The purpose of this article is to argue first that any theorizing on sexual selection in ancestral human societies should be consistent with the anthropological and historical records. Based on this reasoning, it is further argued that systematic evidence from these sources is consistent with the hypothesis that parental choice had been the primary sexual selection force during most of the period of human evolution, and female choice and male-male competition had also been important sexual selection forces. Before discussing the evi- dence from the anthropological and historical records, a brief discussion of each selection force is needed.

The natural order?

From the military chain of command to the multi-tiered organization of academic institutions, hierarchies are a pervasive feature of the modern world. Yet it was not always thus. From what we can tell from the archaeological record and contemporary hunter-gatherers, ancestral human groups were small in scale, broadly egalitarian and with only informal leadership roles, based largely on age or personal attributes. This change would be extraordinary enough but when one considers that many non-human primates also have hierarchies a puzzle presents itself: Why did hierarchies disappear then re-emerge over the course of human evolution? This is the question philosopher Benoit Dubreuil, a post-doc at the Universite du Quebec, Montreal, seeks to address in this new book. Dubreuil’s stated aim is to take a naturalistic approach to this problem, by which he means he wants to explain human social organization with reference to behavioural and cognitive traits that evolved long ago in the human lineage. Human hierarchies are sometimes characterized as simply being scaled-up versions of those seen in non-human primates. Dubreuil argues that human hierarchies and political institutions are in fact quite different and are based on cognitive mechanisms unique to humans. The first chapter deals with the cognitive and motivational mechanisms behind cooperation, norm following, and punishment. The chapter begins by asking whether the egalitarianism of ancestral human societies is the result of a “passion for equality”, and concludes by arguing that although we may have such a passion it is limited and that other factors ultimately determine whether human social arrangements are egalitarian or not. This framing is somewhat peculiar, as it is never made very clear where the idea for such a passion comes from. Furthermore, the intervening sections of the chapter, while relevant to understanding the cognitive

Evolutionary History of Hunter-Gatherer Marriage Practices

BackgroundThe universality of marriage in human societies around the world suggests a deep evolutionary history of institutionalized pair-bonding that stems back at least to early modern humans. However, marriage practices vary considerably from culture to culture, ranging from strict prescriptions and arranged marriages in some societies to mostly unregulated courtship in others, presence to absence of brideservice and brideprice, and polyandrous to polygynous unions. The ancestral state of early human marriage is not well known given the lack of conclusive archaeological evidence.MethodologyComparative phylogenetic analyses using data from contemporary hunter-gatherers around the world may allow for the reconstruction of ancestral human cultural traits. We attempt to reconstruct ancestral marriage practices using hunter-gatherer phylogenies based on mitochondrial DNA sequences.ResultsArranged marriages are inferred to go back at least to first modern human migrations out of Africa. Reconstructions are equivocal on whether or not earlier human marriages were arranged because several African hunter-gatherers have courtship marriages. Phylogenetic reconstructions suggest that marriages in early ancestral human societies probably had low levels of polygyny (low reproductive skew) and reciprocal exchanges between the families of marital partners (i.e., brideservice or brideprice).DiscussionPhylogenetic results suggest a deep history of regulated exchange of mates and resources among lineages that enhanced the complexity of human meta-group social structure with coalitions and alliances spanning across multiple residential communities.

Bridewealth and brideservice as instruments of parental choice.

Abstract In the majority of human societies parents control the mating decisions of their female offspring and choose spouses for them according to their own preferences. This parental choice determines the course of sexual selection, as men who lack desirable characteristics are excluded from reproduction. Parents prefer as sons-in-law men with traits such as industry and good working ability that enable them to be good in providing resources. However, many of these traits are unobserved, while future sons-in-law have the incentive to lie about their abilities. Consequently, parents have to solve the problem of selecting the most capable son-in-law between men who have the incentive to lie. One way to do so is for parents to impose a substantial cost to any prospective son-in-law. By doing so, parents can reliably test the abilities of potential sons-in-law. It is proposed that this cost takes the form of the two most common marriage institutions, namely bridewealth and brideservice, whose primary function is to enable parents to exercise their choice effectively. The determinants of these two institutions are further explored and evidence from the anthropological literature is provided. Keywords: Bridewealth, Brideservice, Parental Choice, Marriage Transactions, Sexual Selection, Honest Signaling Introduction Until recently, researchers interested in sexual selection and human mating failed to take into consideration a characteristic which is unique in our species, namely, the control that parents exercise over the mating decisions of their offspring (e.g. Miller, 2000). In most human cultures known to anthropologists parents do not allow sexual freedom to their offspring, and they control their mating choices by arranging their marriages with individuals of their own choice (Apostolou, 2007b; Broude & Greene, 1983; Frayser, 1985; Minturn et al., 1969; Whyte, 1978). As pre-industrial societies resemble ancestral human societies (Lee & De Vore, 1968), the commonness of this

Parent-Offspring Conflict over Mating: The Case of Beauty

In pre-industrial societies parents exercise a strong influence over the mating decisions of their offspring. As modern pre-industrial societies approximate the way of life in ancestral human societies, human mating behavior should be seen as the outcome of a co-evolutionary process between parental and offspring's mating choice. Both parents and offspring have evolved mating preferences, which enable them to select those mates and in-laws who maximize their inclusive fitness. Following Trivers' (1974) theory of parent-offspring conflict, it is hypothesized that in-law and mating preferences substantially overlap, but also differ with respect to the beauty trait of a mating candidate. This hypothesis is tested on a sample of 292 parents. It is found that the two sets of preferences are strongly correlated, while beauty is preferred significantly more in a mating partner than in an in-law.