Self-domestication: what it is and how it is expressed in evolution.

A Biological process that leads to the privileging of genes related to prosocial behavior.

It is often said that nature is cruel. This popular expression could be true at least from our point of view, considering that many of the beings that populate the planet resort to violence with the firm purpose of surviving (leaving behind scenes that are shocking from the perspective of the human eye).

Such observations led to the suspicion for many, many years that aggressiveness was an adaptive trait, and in fact it could be considered as such if we were to focus only on inter- and intra-species conflict as a criterion for judgment.

However, several theories also suggest that evolution may reward animals (including humans) that do not resort to aggression as part of their behavioral repertoire, through different mechanisms (such as collaboration in obtaining food) that increase their probability of staying alive.

In this article we will address precisely this issue, focusing on an essential concept: self-domestication. Examples of its effects in the behavioral, physiological and morphological sphere of living beings will also be detailed.

What is self-domestication

Self-domestication is a theoretical postulate that proposes that animals, both human and non-human, are subjected to a selection process in which their juvenile traits are particularly retained.. That is, aggressiveness in adulthood would become a counterproductive trait for survival in environments where collaboration is necessary. In this way, the process of adaptation would be facilitated in subjects with a greater capacity for establishing social bonds (more related to early stages of development).

What is really true is that in nature, many animals resort to aggressive behaviors in order to cope with the demands of their environment, since through these behaviors they give the animals a chance to adapt to the demands of their environment.The fact is that many animals in nature resort to aggressive behaviors in order to cope with the demands of their environment, since through them they respond to the usual threats they face in their daily lives. This is an adaptive quality when there are high levels of competitiveness to conquer the resources necessary for survival, but it lacks this virtue in places or historical moments where violence leads to ostracism within the ecosystem (and subsequently to death). In this sense, domestication would be understood as the deepest form of collaboration of two species, and a fundamental example to evaluate the effect of the possible "friendship" of two animals that inhabit the same space ("domos" is a Latin word that translates as "house").

When observing any domesticated animal in detail, not only are changes in its behavioral changes in their behaviors; these transcend morphological, physiological and cognitive dimensions.. For example, scientific evidence demonstrates that such specimens show different pigmentations (softer shades) than other members of their species; as well as smaller teeth, a substantial flattening of the jaw/muzzle projection, a reduction of the cranial perimeter and a substantial similarity with traits characteristic of earlier stages of their physical development. That is, they acquire a friendlier or less hostile appearance.

The natural selection that leads to domestication can happen either automatically or artificially.. The latter case is the best known, the dog/wolf being the most obvious exponent to illustrate it. Today we know that the relationship between man and dog had some difficult beginnings (with numerous attacks on each other), but that it started to improve from chance encounters in which wolves (canis lupus) approached the human territory to peacefully ask for some food.

This non-aggressive approach led to these animals being able to afford the invaluable help of a different species, establishing between the two a future collaboration that would benefit the survival of both. This would give rise to new adaptations of wolves, which would be the most primitive ancestors of what we know as dogs (canis lupus familiaris). This process is based on an interspecies relationship, which has also been reproduced in nature with other animal varieties (spontaneously).

As can be seen, self-domestication necessarily starts from the selection of non-aggressive individuals through integration with other species belonging to the same ecosystem, decisively overcoming the adaptive qualities attributed to aggressiveness (as a tool for confrontation). In this way, would give rise to animals with a much lower tendency to inter/intraspecies attacksas well as with a more refined and prosocial coping style.

What are the differences between domesticated and non-domesticated animals?

The domestication process causes a series of changes in all animals, including humans. The following are the three most important ones, according to the specific dimension to which they may belong: morphology, physiology and behavior.

Morphological changes

In general, it can be said that changes in the animal's appearance are associated with a sort of regression towards the physical characteristics typical of the juvenile stage, in which a softening of the skin and a softening of the body are the main features.In general, it can be said that the changes in the animal's appearance are associated with a sort of regression towards the physical characteristics of the juvenile stage, in which there is a softening of facial features and corpulence in absolute terms. In many of the species studied (including dogs, primates and pigs), skulls with a smaller perimeter (with respect to the average of the species in the wild) and a flattening of the face have been observed, which is known as neoteny (juvenile appearance).

The teeth (which are used as a weapon for aggression) are also reduced in size, and the anatomical discrepancies between the sexes (dimorphism) would be notably diluted, since there is usually greater similarity between the female and juvenile physical appearance in most animal species.

2. Physiological changes

Animals subjected to a process of self-domestication also show a series of changes in the a series of changes in metabolic and endocrine function.. For example, many studies indicate that the hypothalamic-pituitary-adrenal (or HHA) axis is hypoactivated in the basal state (which would result in low levels of stress at rest), but that its function would increase rapidly when competitive (steroid-mediated) stress is required.

Many authors interpret this biphasic response as a tendency towards passive coping styles among self-domesticated animals, as well as avoidance of potentially dangerous situations (unwillingness to act aggressively).

In the specific case of foxes, significantly higher levels of the neurotransmitter serotonin (5-HT) have been observed among those that have undergone a domestication process, this being one of the fundamental neurobiological modulators of active and/or passive aggression responses (with predatory or defensive intent in the face of attacks). Likewise, functional neuroimaging evidence also suggests low levels of limbic reactivity upon exposure to threatening situations. (more specifically an amygdalin hypoactivation), which indicates a reduced experience of fear (this emotion being one of those that most frequently trigger defensive aggression responses).

Finally, it has also been observed that domesticated animals show an alteration in their reproductive cycles, and especially an important increase in their frequency and duration. This physiological process would be accompanied by mating efforts characterized by a reduced incidence of coercive acts (or of imposition by force). (or of imposition by force of the one who enjoys a greater hierarchical dominance), including more sophisticated and relevant (and even more beautiful) mating rituals.

3. Behavioral and cognitive changes

Behavioral changes are, among all those related to the theory of self-domestication, the most numerous and well known. They have been described in a wide variety of different animals, but especially among canids and primates (because they are evolutionarily or relationally close to humans). Thus, for example, it is known that wolves are much more aggressive than dogs (which limit themselves to barking in the presence of a rival group), or that bonobos tend to be more peaceful and tolerant than other species of apes (such as chimpanzees).

It is precisely the latter that have, at least in the last decade, attracted the greatest amount of research. Bonobos and chimpanzees can provide information on the attitudinal/social aspects of the self-domestication process.There is a broad scientific consensus that the former has experienced this in a much more pronounced way than the latter, which merits interesting comparisons of intraspecies interactions in their respective natural environments.

The main conclusions drawn from this are suggestive of the fact that (in general) bonobos are animals with a greater "social commitment" to their family and herd, which manifests itself in a notable tendency to share food (even in cases where the recipient of the food has not collaborated in its search or storage). They are also known to have greater recourse to play and other recreational activities (which have no adaptive purpose in themselves), which has been considered an indirect indicator of intelligence.

Bonobos have also been shown to be more cooperative animals during interactions with other species, including humans, showing more obedience to instructions whose compliance may provide them with incentives of some kind (food, toys, etc.).They appear to be more obedient to instructions whose compliance may provide them with incentives of some kind (food, toys, etc.). Likewise, they also seem much more capable of inhibiting the urge to achieve a quick but discreet reward, preferring to wait for some time to see their reward accrue. This suggests a higher frustration tolerance.

The researchers' findings suggest that bonobos retain many more of the behaviors of their early youth, including those that have a prosocial essence, and that they maintain them throughout their youth.and that they maintain them throughout life. This fact could be one of the consequences of their self-domestication, and could be due to the differential evolutionary process they had to face (with respect to that of chimpanzees). Both the environment and the concomitant circumstances in their respective "histories" have been postulated as explanatory variables for their differences in habits and customs.

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Does it also occur in humans?

Apparently, the answer to this question is yes. Many studies suggest that the changes in our physical appearance with respect to our primitive ancestors (greater cranial sphericity, loss of body hair, decrease in muscle mass, flattening of the teeth, retrotraction of the jaw or general infantilization of the face) are due to this process, and that these changes are also related to our extraordinary hominids. are related to our extraordinary cognitive and social milestones; as well as technological and even creative/artistic ones..

The modern human face has exceptional neotenic properties in nature (youthful appearance). In fact, it is considered that the face of the adult male is very similar to that of an adolescent Neanderthal. This process (which also took place in other extinct hominid species, presenting itself in the form of a mosaic) has developed in parallel with man's move away from wild nature and his approach to societies in which multiple individuals participated (whose functioning required extraordinary cognitive skills).

In short, the changes that resulted from living in large communities and from gathering habits not only shaped our physical appearance, but also the way we look. not only shaped our physical appearance, but also the very way we interact with others and with the environment around us.. The process of human self-domestication, understood as the tendency towards intraspecies collaboration, may be fundamental to understanding who we are and why.