With our limbic sub-brains, we engage with each other in an elaborate emotional information exchange all of the time. We sense the inner states and the motives of nearby mammals by reading their facial expressions, body language, and tone of voice in an unconscious split second. Simultaneously the limbic sub-brain directs the broadcast of information about our inner states for others to collect. All of this is accomplished out of our awareness. The limbic brain collects sensory information, filters it for emotional relevance, then sends appropriate orders to other brain areas thousands of times a day. We can thank our limbic sub-brain for knowing whether to bond with someone or run the other way.

Our ability to bond with others and our need for it is inborn. In the 1940s a researcher studied orphans reared in institutions. The infants were deprived of touch and play because the caregivers believed at the time that they were preventing exposure to infectious organisms. Though their physical needs were met, these children became withdrawn and sickly, and lost weight. A great many of them died. They were emotionally starved.

When an attachment bond is ruptured, mammals react in predictable ways. Short separations bring about a response known as protest, while prolonged separations cause the physiological state of despair. You've seen the puppy's separation protest when he is left alone: pacing, barking, scratching, attempts to scale the walls of his enclosure, and piteous whining.

Most of us have experienced the human version of separation protest when our infatuation with someone was interrupted by their rejection of us. Feeling jilted, we are intent on contacting the person, just to talk; we mistakenly glimpse the lost figure everywhere. We often persist, even when we understand that the other person doesn't want anything to do with us. We write lengthy letters, make frantic phone calls, send repeated e-mails, and telephone an answering machine just to hear the other's voice. That limbic sub-brain knows how to create powerful attachments that are difficult to undo.

Research on rats has shed some amazing details about bonding. In his lab one morning, a researcher noticed that a mother rat had escaped during the night, abandoning her litter of pups. To his surprise, the heart rates of the abandoned pups were less than half of normal. He ultimately decided to test the effect of each specific feature of the bond between the mother rat and her pups: the mother's scent, body heat, tactile stimulation, and milk. He found that a mother rat's scent and warmth directed the pup's activity level, her tactile stimulation determined the pup's growth hormone level, and the milk delivered to the pup's stomach fixed the heart rate. His work showed that the bond itself is woven from separate strands, each with a distinct regulatory pathway in the body.

As mammals, we are physiologically regulated by each other throughout our lifetime with infants being the most dependent upon this external support. In adult humans, medical illness or death often follows the end of a marriage or the loss of a spouse. Some studies indicate that social affiliation increases survival rates from serious illnesses. There is growing evidence that there is a relationship between isolation and human mortality.

Being well regulated in relatedness is the deeply gratifying state that most of us seek ceaselessly in romance and religions, husbands and wives, friends and pets, softball teams and bowling leagues. We thirst for sustaining affiliations. The authors of A General Theory of Love warn that we enjoy today's fast-paced, disjointed lifestyle at our own risk-that we are out of synch with our own biological needs for emotional connection with each other.

From the stand-point of mammal physiology, I believe that practicing interdependence requires us to understand and accept our own deep need for sustaining affiliation. To surrender to our need for emotional connection to each other feels to me to be a kind of reverence for life.

Personally, I am grateful to have a bunch of mammals like you to share joys and sorrows with, and contemplate together how to be in the world. I'm looking forward to our future together as we coordinate our limbic and neocortical brains, best we can, in a search for more understanding of what it means to respect the interdependent web of all existence.

What is your reaction to this sermon? Please send comments to Josie Stultz