Stress, Evolution and The Brain
May 24, 2016 05:29PM
by Sandra Vela
For both sexes, stress has evolved as humans have evolved. In the early days, basic survival depended on humans’ ability to react quickly in a predator-rich environment.
The reptilian, or lower part of the brain was always on high alert and there was little need for high-end cognitive skills or abilities. One of the reptilian brain’s main functions was—and still is—to protect us from perceived threats. This ancient structure has developed as a basic survival mechanism. We learned to repeat the behaviors and habits that had kept us alive the day before.
Our brains are still hard-wired for this type of survival, an evolutionary response to the environment where there is no time for rational thinking, where actions must be taken quickly to protect oneself from harm. The lower brain still interprets all in-coming data as potential threats to survival, but unlike the ancient threats of tigers in the savannah, modern fears cause this survival system to do more harm than good. Today it’s mortgage payments, the demanding boss, caregiving or traffic that overwhelms and keeps us on high alert. Most people experience this response as stress. This primitive system is constantly being triggered, resulting in rash and sometimes impulsive behaviors.
“Stress has evolved from dealing with a single short-term crisis to the ability to turn stress on in a chronic way,” says Robert Sapolsky, author of Why Zebras Don’t Get Ulcers.
When someone perceives a situation as disagreeable or dangerous, a general response is triggered in the body. Depending on the situation and the person’s experience with such situ- Stress, Evolution and The Brain by Sandra Vela ations, he or she will either fight, flight or freeze. Chronic stress can increase stress hormone levels, such as cortisol. The chemical reaction to stress impacts the body and can be experienced as depression or anxiety. Those physiological, chemical and hormonal reactions happening in the body can have long-term health impacts.
The prefrontal cortex—or higher brain—is where conscious control and decision-making processes occur. In low to moderate stress levels, the higher brain usually calms the lower brain system and is able to better consider the pros and cons of any given situation. With extreme or chronic stimulus, the activation of the stress (or lower brain) response shuts off the prefrontal cortex function. When the lower brain perceives stimulus as a threat, the conscious part of the brain automatically gets turned off; known as a lower brain hijack.
New neuroscience research has shown that if neurons in the lower brain receive stress signals continuously from the same stimulus such as workplace hassles, exams or relationship conflict, they become sensitized, making it easier for the lower brain to be hijacked, during which 75 percent of conscious reasoning is lost. Energy sent to the prefrontal cortex is greatly reduced during such episodes. Rational thinking and problem-solving skills is not accessible in this state.
Even psychological threats will activate the lower brain— anything that might impact our sense of well-being or thoughts and emotions that trigger fear, anger or harm. Generally only five percent of the brain is devoted to any given “present” situation and the rest is occupied with thoughts of the past or worries about the future.
Because the hormonal result of stress includes increased blood pressure and circulating blood sugar levels, and a less-effective immune system, chronic stress can lead to serious health problems. Researchers noted in studies published in Psychological Review that men and women deal differently with stress.
For women, relationship loss was one of the biggest stressors, and for men it was performance failure. The study reported that females were more likely to deal with stress by “tending and befriending,” being nurturing and reaching out. This behavior is also linked to primitive responses designed to protect the self and offspring, promoting feelings of safety in order to reduce distress.
Men leaned more toward the tried and true fight or flight response, reacting by suppressing stress, escaping or fighting back. Both sexes, however, exhibited the “freeze” response under stress, which results in life stagnation. This is why making changes can be difficult.
“Men and women need to find ways to deal with chronic stress. This is not what the body has evolved for, and it can increase a person’s risk of everything from heart disease to metabolic disorders to impaired wound healing,” states Sapolsky.
Our prefrontal cortex activates the body’s ability to heal itself, to create new habits, to have insights, sharpen intuition and make decisions that are for one’s highest good. It’s the capacity of the prefrontal cortex to be highly effective and productive, where we experience peacefulness, joy and a sense of abundance. Most of us live our lives caught in this evolutionary lower-brain loop, denying access to our most highly evolved part of the brain—the prefrontal cortex. This part of the brain was designed for dealing with the rapid change of modern life.
To learn more about Higher Brain Living, contact Sandra Vela, Mastery Level Higher Brain Living facilitator, at SandraVela.com or on Facebook at Awakening Austin.