Attachment: Biology, Evolution and Environment

Over the course of thousands of generations, evolution has imprinted in our brains and bodies automatic tendencies that guide aspects of our behavior and social life, such as: responding to threat, danger and loss; bonding with a child and mate; creating and protecting a family. These instinctual reactions have become etched into our nervous systems because they have enabled us to adapt, to handle the recurring challenges of life, and to perpetuate our species.

Attachment between infant and caregiver is a prime example of a behavior pattern that is rooted in biology and evolution. Attachment behavior has become programmed into human beings, and is found to operate similarly in almost all cultures. The purpose and function of attachment is the same regardless of ethnic or cultural differences: to keep the baby close to the caregiver for safety and protection; to allow the child to explore and learn within a safe context ("secure base"); and to develop a loving and reciprocal relationship which can be passed on through generations. To fully understand healthy attachment and attachment disorder, we must consider how this biologically-based process occurs in the context of environmental stimulation, family roles, and brain chemistry.

The nuclear family evolved as the social environment best suited to provide for the needs and development of the young; that is, to foster healthy attachment. Of all mammals, the human baby requires the longest period of nurturance and protection. Instinctual attachment behaviors (clinging, following, sucking, smiling, gazing, touching) emerge within this context of prolonged helplessness and dependency. In order for attachment to occur, however, there must be stimulation from the environment. In other words, the biologically-based attachment behaviors must be activated by signs or signals from caregivers. There are many examples of this reciprocal pattern among various species. The young herring gull opens his beak wide to receive food in response to seeing the red spot on the beak of the parent gull. The duckling follows the first moving object it sees (hopefully the mother); mother is a stimulus moving at a particular rate. These stimuli are called "social releasers", and there are similar patterns operating in human families. The baby's smile evokes powerful feelings in the mother and father. The mother's smile provokes feelings of comfort in the infant. Crying, mutual gazing, holding ("contact comfort") and feeding all provoke strong responses in baby and caregivers. By understanding the interaction between maturation (instinct) and experience (environmental stimulation), we can begin to appreciate the devastating effects of abuse and neglect on the child's attachment. The "prewired" attachment does not emerge without the necessary external (parental) ingredients.

The issues of family roles is also significant when addressing attachment. Again, let's consider male/female roles from the perspective of biology, evolution and adaptation. Humans evolved from isolated gatherers to cooperative hunter/gatherers. Patterns emerged that led to distinctive gender roles. Males became more efficient hunters and females more focused on caring for the young. A monogamous pair, each with specialized roles and responsibilities, provided a context to enhance survival and offer maximal protection and nurturance to their offspring. This social arrangement required a sense of loyalty, deeply felt emotional attachment, and commitment to mutual goals. The women could devote time to maternal functions, trusting that they had their partner's support. The men could leave home base secure in knowing that their mates were faithful while they were away at the hunt. In other words, male/female roles developed out of practical necessity: the need to adapt to the challenges and demands of life.

These same needs are present in today's families: loyalty, trust, security, stability, commitment, cooperation, support. Unfortunately, there are trends operating that prevent healthy adaptation and attachment from developing. In 1995, more than 40% of American families were fatherless (up from 17% in 1960). Each year a half million babies are born to teenage girls. Over three million children were reported maltreated last year (60% increase in the last ten years). Rates of out-of-home placements, prenatal drug exposure and family violence are increasing at an alarming rate. Thus, the function of the family as an environment for safety, security, healthy social learning, and positive emotional attachment, is now questionable.

To further understand attachment, we must consider the function and chemistry of the brain. Our brain is actually composed of three parts ("triune brain"), each evolving at a different time and for a different purpose. The Reptilian Brain, or brain stem, was the first to evolve. It regulates basic life functions (digestion, breathing, reproduction, metabolism), and is responsible for primitive sexual, territorial and survival instincts. The next part of the brain to develop, the Limbic System, accompanied the arrival of the first mammals. This provided the ability to experience emotions, refined the capacity for learning and memory, and created the ability to self-heal (immune system). This part of the brain is the seat of all relationship bonds and controls attachment behavior. The Neocortex is the third and final part of the brain to evolve, and is what makes us uniquely human. It controls thinking, reasoning, creativity, and symbolic language. It enables us to observe our own emotions and (hopefully) have choices about our response.

Thus, much of our social behavior is controlled by the "old brain" (the first two parts to evolve), not by our higher intellect. The old brain governs maternal instinct, attachment behavior, self-preservation, and stress-related responses. When threat or danger is sensed, a part of the Limbic System (amygdala) triggers the release of stress hormones. Norepinephrine increases the brain's overall reactivity, making the senses more alert. Dopamine mobilizes the body for action ("fight or flight"), increasing heart rate and blood pressure, and rivets attention on the source of the fear.

How does this relate to children and attachment? Children with attachment disorder have often been victims of abuse, neglect and multiple separations/disruptions. Their trauma, fear, anxiety and painful emotions are lodged in the primitive portion of their brains ("old brain"). This is why traditional cognitive and behavioral therapy is not usually effective with these children. Conventional therapeutic approaches are directed towards the Neocortex, and this intellectual approach does not provide access to these children in ways that are necessary for healing and positive change. Alternative approaches that promote attachment behaviors are more useful. The holding/nurturing approach, for example, stimulates the part of the brain responsible for attachment. It is often helpful to provide social releasers (eye contact, smile, safe touch, gentle movement) in the holding/nurturing position, for the child who was deprived of healthy attachment.

In summary, attachment is instinctive, rooted in thousands of years of human evolution. Healthy attachment only emerges, however, with certain kinds of cues or signals from caregivers. Maltreatment prevents the natural development of healthy attachment, and triggers the release of stress hormones in the "old brain". We need to understand what children and parents need both in families and in therapy to provide real healing.

© The Attachment Center at Evergreen

Credits: Terry M. Levy, Ph.D.