Tuesday, February 8, 2022

Some suggest that humans are ‘domesticated’ apes; the wolf–dog comparison has been used to support the idea of the human self-domestication hypothesis, but more recent results are not in line with this claim

Comparing wolves and dogs: current status and implications for human ‘self-domestication’. Friederike Range, Sarah Marshall-Pescini. Trends in Cognitive Sciences, Feb 7 2022. https://doi.org/10.1016/j.tics.2022.01.003


Domestication is thought to alter the temperament of a species, making it less fearful and aggressive and more social, thereby promoting their sociocognitive abilities. Some authors suggest that humans are ‘domesticated’ apes.

The wolf–dog comparison has been used to support the idea of the human self-domestication hypothesis, but more recent results are not in line with this claim.

Genetic and behavioral studies of free-ranging, pet, and captive pack-living dogs, as well as different subspecies of wolves, can further our understanding of the dog domestication process.

Current dog domestication hypotheses focus on explaining specific dog–human interactions rather than trying to understand dogs as a social species.

Dog domestication is best understood as an adaptation to a new, human-dominated niche, which included selective pressures by humans.

Abstract: Based on claims that dogs are less aggressive and show more sophisticated socio-cognitive skills compared with wolves, dog domestication has been invoked to support the idea that humans underwent a similar ‘self-domestication’ process. Here, we review studies on wolf–dog differences and conclude that results do not support such claims: dogs do not show increased socio-cognitive skills and they are not less aggressive than wolves. Rather, compared with wolves, dogs seek to avoid conflicts, specifically with higher ranking conspecifics and humans, and might have an increased inclination to follow rules, making them amenable social partners. These conclusions challenge the suitability of dog domestication as a model for human social evolution and suggest that dogs need to be acknowledged as animals adapted to a specific socio-ecological niche as well as being shaped by human selection for specific traits.

Concluding remarks

Although the idea that one selection process might explain the emergence of several traits in humans and domesticated species is exciting, the reality is more complex because species are exposed to different selective pressures in their natural environments. Concerning dogs, their behavior and cognition likely reflect changes in their socio-ecology, going hand in hand with human-enacted selective pressures favoring animals that can be easily inhibited and controlled, allowing humans to exploit the skills of dogs for their own use. However, these data do not support the claims of the HSD hypothesis of a general tamer temperament and higher socio-cognitive skills in dogs compared with wolves. Nevertheless, dog domestication might be a good model to further our understanding of the factors affecting human out-group dynamics and increased propensity for rule-following/adherence to social norms. Finally, we would like to caution researchers to consider the genetic make-up and social experience of their study populations when comparing wolves and dogs. Instead of formulating new domestication hypotheses to explain tiny differences in behavior or cognition, we would like to encourage researchers to also see dogs as a species adapted to their unique ecological niche and not only as a human-made product, and to test hypotheses using different paradigms.
Outstanding questions
Is the difference in fear reactions to humans and human artifacts of wolves and dogs (at least partly) a result of ‘selection for shyness’ in wolves? To investigate this question, different wolf subspecies need to be studied.
Does selection against aggression have a snowball effect on other aspects, such as the social structure of a species? Conversely, does adaptation to a new, more stable foraging niche with small, distributed food items bring about similar changes to those observed during dog domestication? To answer the first question, cognitive and behavioral studies of Belyaev’s ‘tame foxes’, including how these animals interact with conspecifics, would be valuable. To answer the second, a better understanding of how social cognition and behavior changes in canids adapting to an urban environment would be needed.
Which (combination of) hypotheses under which conditions might lead to the observed traits in dogs? Computer models might shed light on this question.
How varied is the social system of both wolves and dogs in the ‘wild’? Can such variability be exclusively explained by the respective ecological conditions? For example, would feral dogs living off hunting (rather than scavenging) show a social structure comparable to that of wolves (e.g., dingoes cooperatively hunt large prey, such as kangaroos)? Or are there consistent differences between the social organization of wolves and dogs, which cannot be explained by the ecological conditions they live in?
Do wolves and dogs perceive humans differently? Do they see humans as social partners at the same eye-level or rather someone to whom they look up to? How much does that depend on specific experiences?
Is the lower inclination of dogs to challenge hierarchies compared with wolves a good model for human evolution? To answer this question, we need to explore whether, compared with chimps (or bonobos), humans are more prone to accept the decisions of their leaders and, thus, avoid potentially costly conflicts with them.

Men & women tend to exhibit meaningful differences in personality & psychopathology, as well as in omnibus morphometry & regional morphometric brain differences, but those differences appear unrelated to the psychological differences

Structural brain differences do not mediate the relations between sex and personality or psychopathology. Courtland S. Hyatt et al. In press at the Journal of Personality, Feb 2022. https://osf.io/dsk53


Introduction: Males and females tend to exhibit small but reliable differences in personality traits and indices of psychopathology that are relatively stable over time and across cultures. Previous work suggests that sex differences in brain structure account for differences in domains of cognition.

Methods: We used data from the Human Connectome Project (N = 1098) to test whether sex differences in brain morphometry account for observed differences in the personality traits neuroticism and agreeableness, as well as symptoms of internalizing and externalizing psychopathology. We operationalized brain morphometry in three ways: omnibus measures (e.g., total gray matter volume), Glasser regions defined through a multi-modal parcellation approach, and Desikan regions defined by structural features of the brain.

Results: Most expected sex differences in personality, psychopathology, and brain morphometry were observed, but the statistical mediation analyses were null: sex differences in brain morphometry did not account for sex differences in personality or psychopathology.

Conclusions: Men and women tend to exhibit meaningful differences in personality and psychopathology, as well as in omnibus morphometry and regional morphometric differences as defined by the Glasser and Desikan atlases, but these morphometric differences appear unrelated to the psychological differences.

Keywords: psychopathology, morphometry, sex, five factor model, human connectome project