The first time I heard about oxytocin, it was from James Herriot telling about using it as an injection to help a pig who was trying to give birth. It worked and he was very pleased. Dunno how the pig felt about it. But I "love" this relationship with oxytocin because it is so down to earth. Er, mud.
Aside from the industry of "love", which like religion promotes the idea that it is some transcendent other-worldly uncontrollable emotional state that some call "limerence" and others call "falling in love," we begin to see that love is a neuropeptide called oxytocin and maybe vasopressin. The evidence is a little rodent called a "vole" which looks like a fat tail-less mouse. Ever so conveniently, one variation is a faithful family man and the other is a rover. They separate according to habitat (homebodies on the prairie, chancers on the mountain) which means that there is something about each ,mutation that is an advantage where they live, but also means that they are ideal for studying this ineffable but often fuckable distinction.
"A social bond is a hypothetical construct of adaptive, relatively enduring processes characterized by proximity seeking between partners, a preference for the partner, stress upon separation from the partner, and the cessation of the stress response at reunion." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5308882/
As the pig knows, there is a transition here between the first "love," which is inclusion, as quite literally inclusion in the mother, which becomes exclusion at birth. But since infants need mothers even when they are outside mom, the new kind of love that had to be present for the sake of mammal survival is attachment. Invisibly, piglets are attached to mom. It's not just as a source of food and warmth, as we have seen with the monkey experiments, infants need cuddling.
"Although pair bonds are most evident in industrialized societies that primarily adopt monogamous life strategies, they occur across all human societies, as do parent-offspring attachments." Ibid. In some ways the pair bond between the two parents (pair-ents) is more important than that between mother and babies, since the survival of the family is enhanced by a functioning dad. If the offspring are lost somehow, the pair can make more. To study monogamous family solidarity, it is necessary to study marmosets and tamarins, predecessors of primates. This is evidently one of the species-linked evolutions about neuropeptides enabled something that improved the lives of the creatures. Maybe there's a clue in that these animals live in trees and are active at night. But once the scientists found the chemical molecules in voles, they were too fascinated to ask why being monogamous would make life better for a prairie vole, or the converse -- why is living in the mountains better for a male free agent? This line of thought is highly relevant in a "post-industrial" age when a lot of dads fail to bond or even to pick up the check. Evidently modern life is rocky.
Mutations that become evolutions are always additive and do not knock out the previous genome. So the capacity to bond, even only temporarily for reproduction, is always on top of the reptilian impulse to compete, destroy, and eat even the previously created infants. Tomcats and grizzly bears kill their offspring, unless the mother prevents them. The same is sometimes true of humans, depending on the failure of a number of small but effective later mutations that prevent indiscriminate violence.
Porges faces this, which makes him very valuable in modern societies where it seems either that the protective mutations weren't passed on, or cultural factors have erased or weakened them. Opposed to oxytocin is not some fancy new drug, but just ordinary alcohol. It lessens the resistance to sex on the one hand and makes it more overwhelmingly aggressive on the other. (Both sexes.) Not only is this problematic for the born child too small to defend itself, but also it distorts the "inclusion" during gestation. These deformations persist into the attachments later, even in adults if they live that long. One of the distortions is lust without love. That is, reproduction without attachment. Without the protective impulse of the proper nucleopeptides, lust can slide to murder.
Much of this behavior is controlled and communicated through smell, the earliest and possibly most powerful of the senses. Also, day length is relevant, and territoriality is characteristic. Once voles are bonded, they only tolerate family. Consider these things in the life of a police officer attempting to keep order at night in territories that are not his. Places that stink.
"Differences in parental behavior received by pups (i.e., high contact vs. low contact parenting styles) are associated with altered social and alloparental behaviors displayed by those pups during their adolescence.. Furthermore, offspring raised by single mothers demonstrate lower levels of spontaneous parental behavior, delayed partner preference formation, and altered anxiety-like behaviors in adulthood, compared to those reared by both parents, further demonstrating the importance of biparental environment for the normal development of the offspring." Ibid.
Inability to attach prevents even choosing a mate, much less sticking with one or remaining monogamous. The ability to attach means that likely the ability to maintain stability in spite of anxiety or outright trauma. This ability in humans is highly dependent on the relationship between baby and carer, which begins with providing milk while maintaining eye contact, progresses from sucking to babbling in response to babytalk and then mirroring. This concentrated attention to each other opens between them a "virtual" space, that is, a shared concept space that isn't actual but is "real" to the two people. Some call it play and others call it liminal. It is a mental/emotional construct, the kernel of what some call spirituality, and the source of cultural sharing. It is what makes us human.
Separation of pair-bonds, as in removing infants from mothers at the Mexican border, throws the individuals into insanity. The growing liminal space is destroyed, possibly for life. It is a murder. This is as true for the men who have attached to their children (the "prairie voles") as for the "mountain voles". We are creating men who take risks and have nothing to lose. Many of the guards are the same kind of men created in US circumstances. Their bars are loud and contentious. The safeguards against reptilian violence are being removed. Nice suburban ladies objecting to kids in cages are simply not relevant. Any industrialized sow could tell them.