RAD arises from a failure to form normal attachments to primary caregivers in early childhood. Such a failure could result from severe early experiences of neglect, abuse, abrupt separation from caregivers between the ages of six months and three years, frequent change of caregivers, or a lack of caregiver responsiveness to a child's communicative efforts.[…]1

Children with RAD are presumed to have grossly disturbed internal working models of relationships, which may lead to interpersonal and behavioral difficulties in later life. There are few studies of long-term effects, and there is a lack of clarity about the presentation of the disorder beyond the age of five years. [2][3] However, the opening of orphanages in Eastern Europe following the end of the Cold War in the early-1990s provided opportunities for research on infants and toddlers brought up in very deprived conditions. Such research broadened the understanding of the prevalence, causes, mechanism and assessment of disorders of attachment and led to efforts from the late-1990s onwards to develop treatment and prevention programs and better methods of assessment. Mainstream theorists in the field have proposed that a broader range of conditions arising from problems with attachment should be defined beyond current classifications.4

The brain development of the child requires, we’re talking about the physiological development of key brain-circuits to do stress responses, emotional-self regulation, impulse-control; attention, decision-making, picking-up on social-cues. Those essential brain-circuits for their physiological development require the presents of non-stressed, emotional available, attuned, parenting caregivers.2

Domestication (from Latin domesticus) is the process where by a population of animals or plants is changed at the genetic level through a process of selection, in order to accentuate traits that benefit humans. It differs from taming in that a change in the phenotypical expression and genotype of the animal occurs, whereas taming is simply the process by which animals become accustomed to human presence.

According to evolutionary biologist Jared Diamond, animal species MUST meet six criteria in order to be considered for domestication:

1. • Flexible diet — Creatures that are willing to consume a wide variety of food sources and can live off less cumulative food from the food pyramid (such as corn or wheat), particularly food that is not utilized by humans (such as grass and forage) are less expensive to keep in captivity.  Carnivores by definition feed primarily or only on animal tissue, which requires the expenditure of many animals, though they may exploit sources of meat not utilized by humans, such as scraps and vermin.

2. • Reasonably fast growth rate — Fast maturity rate compared to the human life span allows breeding intervention and makes the animal useful within an acceptable duration of caretaking.  Large animals such as elephants require many years before they reach a useful size.

3. • Ability to be bred in captivity — Creatures that are reluctant to breed when kept in captivity do not produce useful offspring, and instead are limited to capture in their wild state.  Creatures such as the panda, antelope and giant forest hog are territorial when breeding and cannot be maintained in crowded enclosures in captivity.

4. • Pleasant disposition — Large creatures that are aggressive toward humans are dangerous to keep in captivity.  The African buffalo has an unpredictable nature and is highly dangerous to humans; similarly, although the American bison is raised in enclosed ranges in the Western United States, it is much too dangerous to be regarded as truly domesticated.  Although similar to the domesticated pig in many ways, Africa's warthog and bushpig are also dangerous in captivity.

5. • Temperament which makes it unlikely to panic — A creature with a nervous disposition is difficult to keep in captivity as it may attempt to flee whenever startled.  The gazelle is very flighty and it has a powerful leap that allows it to escape an enclosed pen.  Some animals, such as the domestic sheep, still have a strong tendency to panic when their flight zone is encroached upon.  However, most sheep also show a flocking instinct, whereby they stay close together when pressed.  Livestock with such an instinct may be herded by people and dogs.

6. • Modifiable social hierarchy — Social creatures whose herds occupy overlapping ranges and recognize a hierarchy of dominance can be raised to recognize a human as the pack leader:

    • tapirs and rhinoceroses are solitary and do not tolerate being penned with each other

    • antelope and deer except for reindeer are territorial when breeding and live in herds only for the rest of the year

    • bighorn sheep and peccaries have nonhierarchical herd structures and do not follow any definite leader: instead males fight continuously with each other for mating opportunities

    • musk ox herds (although having a defined leader) maintain mutually exclusive territories and two herds will fight if kept together.

However, this list is of limited use because it fails to take into account the profound changes that domestication has on a species. While it is true that some animals, including parrots, whales, and most members of the Carnivora, retain their wild instincts even if born in captivity[citation needed], some factors must be taken into consideration.

In particular, number (5) may not be a prerequisite for domestication, but rather a natural consequence of a species' having been domesticated. In other words, wild animals are naturally timid and flighty because they are constantly faced by predators; domestic animals do not need such a nervous disposition, as they are protected by their human owners. The same holds true for number (4) — aggressive temperament is an adaptation to the danger from predators. A Cape buffalo can kill even an attacking lion, but most modern large domestic animals were descendants of aggressive ancestors. The wild boar, ancestor of the domestic pig, is certainly renowned for its ferocity; other examples include the aurochs (ancestor of modern cattle), horse, Bactrian camels and yaks, all of which are no less dangerous than their undomesticated wild relatives such as zebras and buffalos. Others have argued that the difference lies in the ease with which breeding can improve the disposition of wild animals, a view supported by the failure to domesticate the kiang and onager. On the other hand for thousands of years humans have managed to tame dangerous species like the elephants, bears and cheetahs whose failed domestications had little to do with their aggressiveness. Number (6), while it does apply to most domesticated species, also has exceptions, most notably in the domestic cat and ferret, which are both descended from strictly solitary wild ancestors but which tolerate and even seek out social interaction in their domestic forms. Feral domestic cats, for example, naturally form colonies around concentrated food sources and will even share prey and rear kittens communally, while wildcats remain solitary even in the presence of such food sources. Zoologist Marston Bates devoted a chapter on domestication in his 1960 book The Forest and the Sea, in which he talks a great deal about how domestication alters a species: Dispersal mechanisms tend to disappear for the reason stated above, and also because people provide transportation for them. Chickens have practically lost their ability to fly. Similarly, domestic animals cease to have a definite mating season, and so the need to be territorial when mating loses its value; and if some of the males in a herd are castrated, the problem is reduced even further. What he says suggests that the process of domestication can itself make a creature domesticable. Besides, the first steps towards agriculture may have involved hunters keeping young animals, who are always more impressionable than the adults, after killing their mothers.

[...]Most definitions of stress are framed in terms of homeostasis—specifically, an organism's response to a deviation—actual or threatened—from a state of homeostasis. For instance, stress has been defined as ‘a threat, real or implied, to homeostasis.’ (McEwen 2000, McEwen & Wingfield, 2003) ‘the reaction of an organism to a perturbation in homeostasis,’ (Salmon & Gray, 1985) and ‘the effect of physical, physiologic, or emotional factors (stressors) that induce an alteration in the animal's homeostasis or adaptive states’ (Kitchen et al. 1987).

“Animals have evolved to be adapted to their environments (more precisely, their ancestors' environments [Tooby & Cosmides, 1990]), which is equivalent to saying that the environment in which an animal's ancestors successfully survived and reproduced is the environment in which that animal is best equipped to maintain homeostasis. If an environment—internal as well as external—were unchanging, homeostasis would never be threatened, and the animal organism would have no need to act or react. However, no environment is static; all environments pose virtually constant challenges to homeostasis. Aversive, noxious, and threatening stimuli are a part of life for all animal organisms. Consequently, a state of complete harmony with the environment or perpetual homeostasis is not attainable (or necessarily desirable) for animals, and maintaining homeostasis is a constant endeavor in animal life (Clark et al. 1997a, Charmandari et al. 2003). The entire collection of homeostasis-maintaining processes (termed ‘allostasis’ by some researchers [McEwen 2000] governs life moment-by -moment in every cell of the animal body (Panksepp 1998). Deviations from homeostasis represent a threat to and reduced chances for fitness; hence, animals have evolved effective mechanisms for detecting and correcting such deviations (Panksepp 1998). The CNS assesses the importance of stimuli to homeostasis and, for those stimuli representing a meaningful threat, organizes and initiates the responses necessary to maintain or restore biological equilibrium (Panksepp 1998). In fact, it has been said that the present day mammalian brain is constructed to seek homeostasis (Panksepp 1998).