Oxytocin Is a Many Splendid Thing: Biochemicals Usurp the Divine
Certain biochemicals occur with particular animal, including human behaviors. Parental and filial love, for instance, correlate with the presence of oxytocin and vasopressin in the brain, and they in turn induce the symptoms of loving. Love is in part an adaptive trait that functions with hormones.
In the Christian
view, God is love, the same sort of love. But we hardly expect the Divine to
possess veins with oxytocin flowing through them. Or if with
A tension therefore exists between neuroscience and spiritual thought, a tension that calls for a rethink of the spiritual doctrine of divine love.
brain, determinism, the divine, hormones, love, neuroscience, oxytocin, parental behavior, science and spiritual thought, vasopressin
To appear in the proceedings of the 1996 Sixth European
Conference on Science and Theology,
In the summer of 1848, an explosion shot a steel rod through
the brain of Phineas Gage, the supervisor of a work gang laying railroad tracks
A child in school steals, cheats, fights, and lies. No matter what adults try, they cannot change him into a responsible and loving boy. Teachers blame his family background; parents call for a special educational program; counselors work on building self-esteem. The current system considers outside intervention the cure. But does the problem lie outside or inside the boy?
“A natural chemical called oxytocin is found to underlie love,” writes Robert Wright (Wright 1994, 351).
Inside your brain lies a hypothalamus, the organ that controls “primitive” behaviors such as sex, aggression, and feeding (Insel, Carter 1995). It produces the two hormones, oxytocin and vasopressin, which then pass through a stalk down to the posterior pituitary gland at the base of the brain for storage and secretion (Greenblatt, Mahesh 1996). Both of these biochemicals evolved from the primordial hormone vasatocin which still endures in lower vertebrates. They also share a similar molecular structure, differing in only two out of their nine amino acids, the building blocks of proteins (Carter, Getz 1993). When released into the body, they bind to specific targets called receptors located in the brain and elsewhere, like keys fitting into locks. The receptors then effect other body parts and, finally, behavior (Insel, Carter 1995).
Medicine has long known the effects of oxytocin on the female reproductive system. It naturally stimulates contractions in the uterus right through the birth process by locking onto specific receptors in the muscles of the uterus, causing them to contract. Not surprisingly, the name “oxytocin” derives from the Greek for “swift birth“ (Hrdy, Carter 1995). Obstetricians inject a synthetic form of it to arouse contractions when labor flags. (The Nobel-prize work of Vincent du Vigneaud in 1953 pioneered its and vasopressin's synthesis.) It also helps control excessive bleeding after delivery. Within seconds after her baby begins to suckle, oxytocin prompts the mother's mammary glands to release milk. As every mother and observant father knows, even the cry of a hungry baby can prematurely stimulate milk let-down; so susceptible is oxytocin release to emotional influences. It also plays a role in coitus, nipple eroticism, the milk ejection reflex, and female sexual responsiveness (Ludwig 1995; Sarlin 1981).
Research into the
source and functions of oxytocin continues. Neuroendocrinologist Hans Zingg of
Maurice Manning and
his colleagues in the Department of Biochemistry at the Medical College of Ohio
Oxytocin's companion hormone, vasopressin, plays a key role in maintaining the volume of water in the body at a constant level, and maintaining the concentration of dissolved substances within narrow limits in the body fluids outside the body cells. Specifically male functions of certain animals, such as marking territorial boundaries with scent, also involve vasopressin (Insel, Carter 1995).
Recent research with
vasopressin and oxytocin enters fields other than medicine. Oxytocin receptors
could play roles in social behavior aside from those already known (Oxytocin
Receptors 1992). Peter Klopfer of
In depth research on the role of these hormones in mammals gained momentum. When first presented with pups, a virgin female laboratory rat usually ignores them, is frightened of them, or eats them. She will tolerate them only when they are introduced to her many times over several days. Then she may even care for the youngsters by licking them, retrieving them when they stray from her side, and crouching over them protectively. But a pregnant rat responds to pups caringly within minutes, even before delivery of her own. In a classic experiment from 1968, Joseph Terkel and Jay Rosenblatt of Rutgers University injected virgin female rats with blood from rats that had just given birth. It took the virgins less time to nurture pups than normally (Hrdy, Carter 1995).
Parent rats can
mistreat their children if antagonists block their oxytocin receptors,
according to the research of Cort Pedersen and Jack Caldwell at the University
of North Carolina, and Gustav Jirikowski at Scripps Research Laboratory (Schrof
1991). Parent rats injected with
antagonists to block their oxytocin receptors mistreat their offspring.
Oxytocin release also induces grooming behavior in rats (van Erp, et al. 1995), and when
Voles are small, brown, nondescript mammals of the genus Microtus which live under seeds and grasses (Carter, Getz 1993). Members of one species, the prairie vole, share elaborate systems of burrows and feeding tunnels. Males and females form long-lasting bonds, unlike most rodents, raising their young together. But montane (or mountain) voles occupy separate burrows and avoid each other except to mate -- which they do often and indiscriminately. Mother montane voles usually abandon their pups sixteen days after birth, and fathers never see their offspring. When a predator plucks a youngster from its nest, it neither calls for help nor surges with stress-related hormones. In comparison with their prairie cousins, the high-meadow montane voles lack family values and are exceptionally asocial (Ezzell 1992b; Insel, Carter 1995). Why?
Mapping the oxytocin receptors of vole brains to see where the hormone acts, reveals many more in key areas of prairie brains than in montane's (Insel, Carter 1995). Thomas Insel, now at Emory University, and Larry Shapiro of the National Institute of Mental Health's (NIMH) facility in Poolesville, Maryland, found that prairie voles have three times the number of oxytocin receptors in their prelimbic cortex -- and seven times more in their nucleus accumbens -- than do montane voles. And during the brief period in which female montane voles nurse their young, the number of their oxytocin receptors surges (Ezzell 1992b). Thus the distribution pattern of oxytocin receptors matches with monogamy and care for offspring, suggesting that oxytocin plays an essential role in social organization (Carter, Getz 1993; Winslow, et al. 1993). We should not conclude, however, that this represents a cause-and-effect relationship between the hormone and behavior (Insel, Carter 1995). Further research does lead to this conclusion, however.
As soon as the
female prairie vole becomes sexually active, she and a male will copulate
repeatedly, more than fifty times over 36-48 hours. After such a bout, she
becomes more socially exclusive, preferring her mate to unfamiliar males. This
discovery by Diane Witt of the University of Maryland suggests that mating
instills long-term pair bonding. Copulation causes the release of oxytocin; is
this the critical factor in developing her social preferences (Insel, Carter
1995)? Jessie Williams, also of the
University of Maryland, found that a female prairie vole rapidly forms a
preference for a male if exposed to oxytocin for six hours. But when
Studies of domestic sheep by Barry Keverne, Keith Kendrick, and their colleagues at the University of Cambridge, add to this picture of the behavioral effects of oxytocin. As a lamb moves down its mother's birth canal, it stimulates nerves that trigger the release of oxytocin. Only with it present at birth or injected so it reaches the brain the same time mother ewe meets her newborn, does she bond with her offspring. She rejects her lamb if something blocks its release. High levels of oxytocin also occur in her milk, suggesting the hormone helps forge a mutual attachment between the mother and her infant (Hrdy, Carter 1995).
What about males' sexual and parental behavior? After the initial sexual bout, a male prairie vole prefers his mate and ferociously guards against rivals, even in her absence (Insel, Carter 1995). James Winslow, while at the NIMH in Poolesville, found that a male isolated from females and injected with vasopressin becomes aggressive and attacks other males. If exposed to a female and injected with vasopressin, a male develops a preference for her even if they do not mate. Administering a vasopressin antagonist to a male ready to mate does not prevent repeated and intense copulation. But afterwards he does not fend off intruders or prefer his partner. (Females respond very little to vasopressin (Carter, Getz 1993; Insel, Carter 1995).) On the other hand, an oxytocin antagonist alters neither the male's mate preference nor his guarding behavior. Zuo-Xin Wang, Craig Ferris, and Geert De Vries, of the University of Massachusetts in Amherst, found that vasopressin also increases (and a vasopressin antagonist decreases) the amount of time he spends with his pups, which he would typically and naturally do by retrieving them and huddling over them; many biologists believe such paternal care for the young anchors male monogamy (Carter, Getz 1993; Hrdy, Carter 1995; Insel, Carter 1995). Only vasopressin, then, accounts for male sexual and parental behavior.
Vasopressin and oxytocin are crucial for pair bonding, eliciting parental care and nurturing, and defending the family (Carter, Getz 1993; Hrdy, Carter 1995). While oxytocin encourages social contact, however, vasopressin compels the males' antisocial, guarding behavior after copulation. The hormones counter each other; their behavioral and cellular functions oppose each other in some circumstances. Perhaps oxytocin blocks the unfriendliness induced by vasopressin. No matter what the mechanism involved, vasopressin and oxytocin together determine for many species if a pair bond, nurture and care for their young, and defend the family. Monogamy and polygyny express the net outcome of what happens when oxytocin and vasopressin activate different circuits in the brain (Carter, Getz 1993; Insel, Carter 1995).
What about in humans? The human brain manufactures vasopressin and oxytocin which bind to receptors there; our forebrain contains many oxytocin receptors, Swedish researchers report (Ezzell 1992b). Though they are large molecules and do not readily penetrate the blood-brain barrier, they exist in larger-than-normal quantities in the brain when hard at work elsewhere in the body. Thus they could in principle influence our social behavior (Ezzell 1992a; Insel, Carter 1995). Much maternal behavior in an expectant mother arises from hormonal changes that her system induces, and after birth it usually stems from hormones her offspring stimulates (Rosenblatt 1994). A sensitive period for this bonding occurs an hour after birth -- when her oxytocin level rises markedly (Nissen, et al. 1995). Breast feeding causes some of the stimulation. In addition, the hormones released by it benefit the mother's mental health and her ability to deal with stress; they calm her (Hrdy, Carter 1995).
A British study of male medical students shows that vasopressin enters the bloodstream during sexual arousal, and oxytocin at orgasm (Carmichael, et al. 1994; Insel, Carter 1995). In both female and male humans, oxytocin levels rise dramatically during sex, and may promote the associated feelings of love and infatuation (Schrof 1991). Kerstin Uvns-Moberg of the Karolinska Institute in Stockholm has shown that a simple touch can release oxytocin (Carter, Getz 1993). We share many of the oxytocin and vasopressin responses of other animals.
According to Webster's New World Dictionary, love is “a deep and tender feeling of affection for or attachment or devotion to a person or persons;...a feeling of [unity and cooperation] and good will toward other people;...a strong, usually passionate, affection of one person for another, based in part on sexual attraction.” “Agape” it defines as “spontaneous, altruistic love.” Oxytocin fosters friendship, love, and nurturance. With vasopressin, it provides the chemistry of human attachment: sticking with your sexual partner and attention to your offspring. Says Cort Pedersen, “Human relations are influenced by the model of the parent-child relationship in that they include the notions of nurturing, care, help” (Schrof 1991). These behaviors we call love; earlier times would call it charity. Love derives from the positive effects of oxytocin and vasopressin.
“Children need love,” writes Harold Hulbert in a 1949 issue of the Reader's Digest, “especially when they do not deserve it.” Sometimes we love despite ourselves, and the involuntary release of oxytocin serves well the survival of our offspring, and with them, our genes. Can we decide to love, and do so, even if this means the decision prompts the release of hormones? This is a crucial question. Though oxytocin and vasopressin from the hypothalamus seem to mandate social attachments among voles, they and other hormones do not fully determine what happens. No hormone acts alone (Schrof 1991). A mother's behavior and experience, for instance, both affect and are affected; exposure to pups reorganizes the neural pathways in a mother rat's brain, making her respond faster to pups in the future no matter what her hormone level (Hrdy, Carter 1995). A human mother can make her milk let-down by thinking about it; the thought spurs the release of oxytocin which in turn primes her mammary glands. Many factors -- especially the complex activities in our cerebral cortex -- intrude on the effects of the hormone in humans (Insel, Carter 1995). That does not mean we can take the opposite position to the naturalist and say that in humans love is only a product of the will. Love is an adaptive trait, both a willed and an involuntary phenomenon (often a combination of both), but it always involves the release of biochemicals.
I write the above though it is at this point speculative. For instance, why is it that quite different mammals exhibit monogamy? Sue Carter of the University of Maryland, and Lowell Getz of the University of Illinois, suggest it may result from the interactions between the adrenal and gonadal hormones in early life, but at this time it is only a hypothesis open to further exploration. Further, excessive amounts of oxytocin in the brain feature in a type of obsessive-compulsive disorder, the sort that sparks fears of germ contamination that lead to hours of hand washing each daysto the point of rubbing off skin and disrupting all other activities. It is the type that consists of repeated, upsetting thoughts or images linked to acts that a person feels compelled to carry out (Bower 1994; Leckman 1994). So oxytocin induces negative effects and only sometimes can we associate it with love. (You could look at the disorder, though, as a way of over-caring, carrying the usual results of oxytocin to an extreme.) It is appealing to ascribe the love role to oxytocin, but it is difficult to prove a causal association objectively, especially with such a large number of variables. Further, the roles of vasopressin and oxytocin are difficult to document, even in animals, and many questions remain unexplored or only partly explored (Carter, Getz 1993). We need to be cautious when we extrapolate data derived from animal or limited human studies. The important point, though, is that love has a biological rootedness, despite what else it involves.
Social bonds have a biology (Carter, Getz 1993). Love is in part a physical trait derived from evolution. Parental and filial love are associated with the hormones oxytocin and vasopressin which promote the behaviors and symptoms of loving. When people love this way, these chemicals occur in their bodies in larger-than-normal amounts. Love functions with them. The dictionary also defines love as “God's tender regard and concern for [hu]mankind.” “Love is from God; everyone who loves is born of God and knows God,” writes Saint John (1 John 4:7-8, The New Testament and Psalms: An Inclusive Version). Jesus talks of his wanting to gather together the people of Jerusalem “as a hen gathers her brood under her wings” (Matthew 23:37). The Gospel of John compares the love of the Divine to a good shepherd who would die for the sheep (John 10:17). Parental, filial, altruistic love -- the oxytocin-vasopressin behavior -- originates in the Divine. But this leads to a confusion: the hormonal behavior of love arises from both the biology of our bodies and from the Divine. It has two different sources. We may not say the same about many “sinful” behaviors.
Saint John continues his epistle with these words: “Whoever does not love does not know God, for God is love.” The Divine is love; does that mean the Divine is pure oxytocin and, because God is a male, also vasopressin? Since we have them, should the Divine possess two hands, each with five fingers? Does the Divine crave food and sex, and does the chemical oxytocin flow through divine veins when the Divine loves? Of course not. The Divine is not a biological being that evolved under environmental pressures, and so does not have hands and fingers, the need for food and sex, or veins throbbing with oxytocin. Love evolved biologically; it pertains to organic creatures -- voles, rats, sheep, humans -- that developed under the imperative to survive genetically. An adaptive trait like love features specifically in animals like humans. So, why should the Divine have love? Love and biochemicals and genes belong together.
Not only does the Divine love us, but the New Testament urges us to love one another. If love derives largely from involuntary releases of biochemicals, is it reasonable to urge people to love each other? Could Gage, the man with a hole through his head, have changed his ways?
These difficult questions challenge the traditional view of the nature of the Divine and the Divine's relationship to us humans. They ask about the association of love with the Divine. So what is a spiritual understanding of love in the light of this new research? What role does the Divine play in love? An answer could take several paths. It could justify the elevation of love from the animal to the level of the Divine. Or it could make sense of how a divine property could become one that, with its biochemical associates, biological beings experience. Or it could start its understanding of the Divine from scratch, asking anew what is the nature of the Divine. To say that the Divine's relationship with the universe and humans is or is like love requires serious reconstruction and justification.
Whatever, an answer should emphasize the relevance of scientific and spiritual ideas for each other. This means actively exploring such points of contact as the nature and origin of love, its connection with the Divine, and the relationship between the Divine and human beings. In the larger enterprise of the partnership between scientific and spiritual ideas, it means working out a flexible system of spiritual ideas that moves with scientific advances, that builds on the findings of science and adopts a method like science's. It means exploring the spiritual scientifically, offering hypotheses and insights for scientific scrutiny. And it means promoting a science that seeks advances in spiritual thought. Spiritual thinkers and scientists could see themselves working in tandem with each other.
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Copyright © 1999 by Kevin Sharpe.