Friday, October 4, 2019

Evolutionary Origins of Morality: The element of prosocial concern most likely evolved in the context of shared infant care, which can be found in humans and some New World monkeys

Evolutionary Origins of Morality: Insights From Non-human Primates. Judith M. Burkart, Rahel K. Brügger and Carel P. van Schaik. Front. Sociol., July 9 2018.

The aim of this contribution is to explore the origins of moral behavior and its underlying moral preferences and intuitions from an evolutionary perspective. Such a perspective encompasses both the ultimate, adaptive function of morality in our own species, as well as the phylogenetic distribution of morality and its key elements across primates. First, with regard to the ultimate function, we argue that human moral preferences are best construed as adaptations to the affordances of the fundamentally interdependent hunter-gatherer lifestyle of our hominin ancestors. Second, with regard to the phylogenetic origin, we show that even though full-blown human morality is unique to humans, several of its key elements are not. Furthermore, a review of evidence from non-human primates regarding prosocial concern, conformity, and the potential presence of universal, biologically anchored and arbitrary cultural norms shows that these elements of morality are not distributed evenly across primate species. This suggests that they have evolved along separate evolutionary trajectories. In particular, the element of prosocial concern most likely evolved in the context of shared infant care, which can be found in humans and some New World monkeys. Strikingly, many if not all of the elements of morality found in non-human primates are only evident in individualistic or dyadic contexts, but not as third-party reactions by truly uninvolved bystanders. We discuss several potential explanations for the unique presence of a systematic third-party perspective in humans, but focus particularly on mentalizing ability and language. Whereas both play an important role in present day, full-blown human morality, it appears unlikely that they played a causal role for the original emergence of morality. Rather, we suggest that the most plausible scenario to date is that human morality emerged because our hominin ancestors, equipped on the one hand with large and powerful brains inherited from their ape-like ancestor, and on the other hand with strong prosocial concern as a result of cooperative breeding, could evolve into an ever more interdependent social niche.


Contemplation of law as a natural social phenomenon quickly reveals that it cannot be reduced to purely rational processes and explicit reasoning. It is fundamentally built on (albeit not identical with) our sense for morality, the propensity to differentiate actions, decisions, and intentions between those that are proper and right and those that are improper or wrong (Long and Sedley, 1987). This evaluation can be the result of deliberation, but also of automatic proximate mechanisms such as intuitions that are expressed by a variety of moral emotions, motivations, and preferences which often have a high-urgency feel (Weaver et al., 2014).

Social scientists have traditionally considered morality as a recent, purely cultural innovation, seemingly necessary to keep our otherwise brutish nature under control (e.g., reviewed in Long and Sedley, 1987; de Waal, 2006; Haidt, 2013). In support of this conjecture, what is considered moral in a given culture or society, or what the corresponding systems of laws prescribe, can indeed be quite variable. However, despite this variability in the content of what counts as moral among cultures, there are also elements that seem universal, both with regard to the proximate mechanisms that regulate moral behavior and the content of moral norms. For instance, Barrett et al. (2016) found that across societies, including small-scale societies, humans take an agent's reason for action into account for moral judgments, but they also found independent variation when looking at specific contents, e.g., harm vs. theft, or in how the content influences the role of intentionality. Furthermore, even if conformist transmission could in principle stabilize a variety of behaviors and norms (Chudek and Henrich, 2011), there appears strong canalization in that some kinds of content (such as for instance not to harm others, or engage in parental investment) are more readily considered moral than others (van Schaik, 2016).

Ubiquitous key elements of human morality discussed in this paper are prosocial concern and conformity, as well as the moral contents of doing good, not harming others, and avoiding inequity and incest (van Schaik, 2016). Importantly, these elements are not only expressed when the individual is personally involved, i.e., in individualistic or dyadic contexts, but also in the absence of personal involvement, i.e., in third-party contexts. For instance, moral behavior not only includes the urge to conform to the rules and norms of one's own community, but also evokes strong feelings that others ought to do so as well. The universal presence of these elements of morality across human societies suggests there is an evolved core to morality, which should therefore be amenable to a functional and comparative evolutionary analysis sensu Tinbergen (Tinbergen, 1963; Bateson and Laland, 2013).

Such an evolutionary analysis claims that whenever universal, proximate mechanisms have evolved, they must have done so to fulfill a specific adaptive function. In the first section of this contribution we will argue that the adaptive function of our evolved morality was to enable the highly interdependent life-style of Pleistocene hunter-gathers.

An evolutionary analysis of human morality also includes the examination of its phylogenetic origin, to which we will turn in the second section. Whereas full-blown human morality, which includes explicit moral reasoning and evaluation, may well be unique to humans, some of its elements or building blocks are not, and we can use data from non-human primates to trace the evolutionary history of each of them separately. An obvious first, and very popular, step is to look at the great apes, and in particular the chimpanzees and bonobos (e.g., de Waal, 2006), to investigate the possible presence of a specific building block in our closest relatives. However, a broader and more informative comparative approach consists in mapping the presence or absence of each of these building blocks or traits in a broader set of species, to then test which factor best predicts this pattern of distribution (MacLean, 2016). If the specific case of humans fits such an identified pattern, this allows us to identify the evolutionary context of the emergence of this trait. This approach thus ideally allows not only to identify that a trait is or is not unique to humans, but also why it is present in a given set of species, including humans.

Beauty is an emergent property: The Neural Selection and the Emergence of ‘beauty Canons’ as Signaling Codes in Co-evolving Species

Formenti, Alessandro. 2019. “The Neural Selection and the Emergence of ‘beauty Canons’ as Signaling Codes in Co-evolving Species.” PsyArXiv. September 29. doi:10.31234/

Widespread opinion wants beauty to be pleasant and aimless, this assumption biased Darwin's explanation of sexual selection. Conversely, Wallace hypothesized that showy and symmetric sexual traits correlate with vigor and health and he placed ‘aesthetic’ preferences within the natural selection. The controversy has continued until today.
To understand the role of beauty canons in communication, the focus was on the flower-pollinator cooperative system as a model, were flower evolution embodies the natural history of pollinators' preferences.
Optimum for a signal requires energy efficiency, high signal-to-noise ratio, and intelligibility. It involves pollinator perception mechanisms that, in turn, induce co-evolutionary feedback on signal traits. In fact, the flowers physical and hedonic properties correlate with the basic perceptual, motivational, emotional, and learning mechanisms of pollinators.
It is proposed that pollinator behavior, unmasking a preference, reveals the ability to evaluate an expected benefit. Features such as a relative simplicity, redundancy, and regularity of stimuli facilitate perception and memorization and are essential elements for communication between co-evolving species. They improve signaling to satisfy the need for easy and fast recognition. With these properties, a stimulus is adaptive and rewarding per se and may be an ideal conditioned stimulus in associative learning.
Among the most conspicuous signals, pollinators learn to recognize and choose those associated with nectar, thus favoring the evolution of flowers that are not only ‘beautiful’ but also ‘honest’ in reporting a reward. Beauty is an emergent property, and studying communication and perception we may understand the origin of some beauty canons.

Some healthy males do not mate when they have access to a sexually receptive female; these non-copulating individuals have been reported in murine, cricetid and ungulates; in humans this is denominated asexuality

Motivational Drive in Non-copulating and Socially Monogamous Mammals. Wendy Portillo and Raúl G. Paredes. Front. Behav. Neurosci., Oct 4 2019.

Abstract: Motivational drives guide behaviors in animals of different species, including humans. Some of these motivations, like looking for food and water, are crucial for the survival of the individual and hence for the preservation of the species. But there is at least another motivation that is also important for the survival of the species but not for the survival of the individual. Undoubtedly, sexual motivation is important for individuals to find a mate and reproduce, thus ensuring the survival of the species. In species with sexual reproduction, when males find a female in the appropriate hormonal conditions, they will display sexual behavior. However, some healthy males do not mate when they have access to a sexually receptive female, even though they are repeatedly tested. These non-copulating (NC) individuals have been reported in murine, cricetid and ungulates. In humans this sexual orientation is denominated asexuality. Asexual individuals are physically and emotionally healthy men and women without desire for sexual intercourse. Different species have developed a variety of strategies to find a mate and reproduce. Most species of mammals are polygamous; they mate with one or several partners at the same time, as occur in rats, or they can reproduce with different conspecifics throughout their life span. There are also monogamous species that only mate with one partner. One of the most studied socially monogamous species is the Prairie vole. In this species mating or cohabitation for long periods induces the formation of a long-lasting pair bond. Both males and females share the nest, show a preference for their sexual partner, display aggression to other males and females and display parental behavior towards their pups. This broad spectrum of reproductive strategies demonstrates the biological variability of sexual motivation and points out the importance of understanding the neurobiological basis of sexual motivational drives in different species.


Mammals display several reproductive strategies that can be influenced by population density, group size, distribution, home range size, abundance of food and resources. In mammals, the most common mating strategy is polygamy with the polygyny (one male more than one female) and polyandry (one female, more than one male, rare or inexistent in no human species) as subtypes. In polygamy, there is no sexual exclusivity and reproductive success is maximized through multiple mating partners (Kleiman, 1977). Social monogamy is a reproductive strategy in species in which resources are evenly distributed but sparse, females can disperse and have large home ranges, and males are not able to defend the access to more than one female. Also, a low density of females and food can favor monogamy. Monogamy is also present when successful rearing of offspring requires paternal and maternal care. Males help carry the litter, provide food for them and the mother when this resource is energetically costly to obtain, and the litter size is larger (Clutton-Brock and Harvey, 1978). Socially monogamous males and females after mating establish a pair bond that can last more than one reproductive cycle. However, in monogamous species some males and females do not form this pair bond and only mate opportunistically.

Interestingly, there are males and females in polygamous and socially monogamous species that do not mate even if they have the opportunity. In humans, around 1% of healthy men and women are not interested in engaging in sexual activity and are denominated as asexual. However, asexual individuals are interested in other motivational aspects of sexuality such as romantic relationships (Bogaert, 2004; Prause and Graham, 2007; Brotto and Yule, 2017; Jones et al., 2017). The biological bases of asexuality in humans are not well understood due to their complexity and ethical issues. However, the physiological bases of asexuality have been studied in murine, cricetid and ungulates, where some males do not mate even if they are tested with several sexually receptive females. In this manuscript, we will briefly outline different motivational strategies associated with reproduction in mammals and then we will describe in more detail the possible neurobiological factors associated with non-copulating (NC) males and the socially monogamous prairie vole.

In most mammals, sexual behavior consists of stereotyped movements usually organized in predictable patterns that are similar between individuals, but which vary between species. The specific patterns displayed by males and females reflect the motivational or consummatory aspects of sexual behavior. The comparative analysis between species showing different mating strategies including monogamy, polygamy and the case of asexuality could help us understand the biological variability of sexual motivational drives in mammals.

People Represent Mental States in Terms of Rationality, Social Impact, and Valence: Validating the 3d Mind Model

Thornton, Mark A., and Diana Tamir. 2019. “People Represent Mental States in Terms of Rationality, Social Impact, and Valence: Validating the 3d Mind Model.” PsyArXiv. June 24. doi:10.31234/

Abstract: Humans can experience a wide variety of different thoughts and feelings in the course of everyday life. To successfully navigate the social world, people need to perceive, understand, and predict others’ mental states. Previous research suggests that people use three dimensions to represent mental states: rationality, social impact, and valence. This 3d Mind Model allows people to efficiently “see” the state of another person’s mind by considering whether that state is rational or emotional, more or less socially impactful, and positive or negative. In the current investigation, we validate this model using neural, behavioral, and linguistic evidence. First, we examine the robustness of the 3d Mind Model by conducting a mega-analysis of four fMRI studies in which participants considered others’ mental states. We find evidence that rationality, social impact, and valence each contribute to explaining the neural representation of mental states. Second, we test whether the 3d Mind Model offers the optimal combination of dimensions for describing neural representations of mental state. Results reveal that the 3d Mind Model achieve the best performance among a large set of candidate dimensions. Indeed, it offers a highly explanatory account of mental state representation, explaining over 80% of reliable neural variance. Finally, we demonstrate that all three dimensions of the model likewise capture convergent behavioral and linguistic measures of mental state representation. Together, these findings provide strong support for the 3d Mind Model, indicating that is it is a robust and generalizable account of how people think about mental states.