The Embodied Mind

How body, brain, and emotion become intertwined.

Survival Mode and Evolutionary Mismatch

Environments ill-suited to our biology often trigger stress and pain.

Many people seem to believe that we human beings never arose from nature the way every other living thing did, that we are somehow “beyond,” removed from, nature. But this is a very unfortunate – even a tragic – misconception. Like all other living things, our ancestors were sculpted by Darwinian evolution to survive, reproduce, and thrive within a certain kind of environment. And when we live in environments, such as modern cities, that are drastically different from the environments that we’re biologically adapted for, we become subject to various “evolutionary mismatch” effects that can be extremely detrimental to our physical and emotional health. Perhaps the most important consequence of this mismatch is that we become highly prone to being triggered repeatedly and unnecessarily into various states of “survival mode” by our surroundings and circumstances. As we’ll see later, another even more destructive dynamic, which also seems to operate only when our lifestyle is mismatched with our biology, can further reinforce these survival-mode states in us.

Human beings are designed biologically almost exclusively for the hunter-gatherer lifestyle. Before twelve thousand years ago, when agricultural methods were invented and began to spread, every person on this planet lived as a hunter-gatherer, and humans or pre-humans had done so for hundreds of thousands of years. We know about hunter-gatherer life mainly from studies of contemporary hunter-gatherers, who live in isolated pockets of the world, and whose lifestyles appear to still be broadly similar to those of our hunter-gatherer ancestors. Hunter-gatherers generally travel in small bands of roughly twenty-five to forty people, and survive by hunting wild animals, and gathering wild fruits, vegetables, nuts, and other occasional delicacies, such as eggs or honey. Before the development of agriculture and animal husbandry, there was simply no other way to make a living.

And while there have been some genetic changes in human beings in the last twelve thousand years, those changes appear to have been relatively superficial – affecting skin color and hair color, for example, or the ability to digest milk as an adult. These genetic changes certainly don’t appear to have altered the basic hunter-gatherer design principles of our brains and bodies in any significant way during this relatively short evolutionary period.

One of our key design principles is that we’re built to be triggered into survival mode whenever our survival is perceived to be at significant risk. Survival mode, however, isn’t only an overt state of fear, or the primal terror of being torn apart by a jaguar or grizzly bear. Whenever we feel any kind of pain or emotional distress – whether it’s self-pity, for example, or guilt, or shame – we’re thrown, operationally, into a state of survival mode. Indeed, the biological reason that unpleasant emotions become triggered within us in the first place is to alert us that our survival may be at risk, and to motivate appropriate action to address that risk. When we have intense feelings of emotional pain during a breakup, for example, the feeling is telling us that a relationship that’s very important to us may soon be lost, and the pain is biologically designed, in a broad sense, to motivate behavior that may help us to preserve the relationship if we possibly can.

But while our relationships today are, of course, critical to our well-being, the overwhelming, gut-wrenching, survival-mode pain we can feel when our intimate relationships are threatened only truly makes sense in the context of our hunter-gatherer past. A human being, especially one without sophisticated tools or weaponry, is very unlikely to survive alone in the wilderness for long, and so our hunter-gatherer ancestors absolutely and categorically relied on their relationships for their survival. Because of this evolutionary heritage, we are all designed to treat our close relationships as if they were of potentially life-or-death significance.

The extraordinarily high levels of social isolation found today provide perhaps the most important current example of evolutionary mismatch. When people feel that they lack supportive, loving relationships, when they feel lonely for extended periods, the consequences can be devastating. Social isolation has been shown to have effects on physical health that are comparable to not exercising or even to smoking cigarettes, and loneliness is also a major risk factor for most psychological syndromes, including severe depression. For hunter-gatherers, lacking close relationships or being socially isolated within the group is truly life-threatening. Food shortages due to a drought, for example, may force the band – not out of callousness, but simply out of survival necessity – to shed one or more band members so that the rest of the band has enough food to survive. The fewer strong attachments any specific hunter-gatherer has to the other people in the band, the greater the chance he or she will be abandoned by the band, and consequently, in all likelihood, left alone to die in the wilderness. The intense feelings of emotional pain lonely people often experience are a consequence of this evolutionary heritage – those feelings are a signal that complete abandonment may be imminent, and that survival is very much at issue.

But the catch is that in modern life, being alone more than one might like is rarely a serious survival threat. It may not feel good to consistently have nothing to do on a Saturday night, but that on its own is almost never a sign that your life is at serious risk. Because of our hunter-gatherer past, however, being alone too much often triggers a survival-mode state in us that, like all survival-mode states, creates stress and releases stress hormones throughout our bodies and brains. And chronically high stress levels seem to be largely responsible for the physical and psychological health issues that lonely people are at higher risk for. So the cruel irony is that, although being socially isolated is rarely an actual survival threat in modern, industrialized cultures, the state of being lonely does trigger stress and survival-mode states because of our hunter-gatherer past, and so being socially isolated does often end up creating a survival risk – but mainly because of chronically elevated stress levels driven by unnecessary and inappropriate survival-mode states. The brain is, in effect, tricked – typically unconsciously – into unnecessary states of survival mode, such as fear of abandonment, not because of actual survival-threatening circumstances, but because our brains confuse our evolutionary past with our modern circumstances. Every modern life is lived in the teeth of massive evolutionary mismatch, and the typical result is that we have far, far more survival mode in our lives than is healthy for us.

My colleague Todd Ritchey and I have suggested that an additional dynamic operating in nearly all of us can also profoundly reinforce unnecessary survival-mode states. A great deal of evidence from neuroscience studies suggests that the stress hormones released by survival-mode states like fear or anxiety have many of the same effects in the brain as addictive drugs like cocaine or methamphetamine. It’s been known for decades, for example, that an integral part of the stress response is the release of endorphin, which many studies have shown is the primary “pleasure” chemical in the brain – that is, whenever we feel pleasure or euphoria, the pleasurable feeling appears to be due largely to the release of endorphin within our brains. But because endorphin release is also involved in the stress response, any sort of stress or pain will also release endorphin into our brains. What Todd Ritchey and I have suggested is that while stress and pain are typically not consciously perceived as being pleasant, nearly all of us receive unconscious biochemical rewards from our pain and emotional distress, and nearly all of us consequently develop literal biochemical addictions to at least some of our painful, distressing, out-of-balance, survival-mode states.

When people with clinical depression, for example, are told to think of sad or painful thoughts, such as the memory of a painful breakup, brain-imaging studies have shown that endorphin is instantly released into their brains. One of the hallmark features of depression is being stuck on a treadmill of painful thoughts and emotions: feelings of regret and shame about the past, for example, or hopelessness about the future. Each of these painful thoughts that arise from the depressed state, we have suggested, provides an unconscious biochemical reward in the brain, and thus the state of depression can become reinforced by a biochemical addiction to the distressing emotions that accompany those painful thoughts.

Although some people are more genetically susceptible to depression than others, hunter-gatherer studies support the idea that clinical depression is largely due to evolutionary mismatch and what may follow from that mismatch. A careful and extensive study of the Kaluli hunter-gatherers of the New Guinea highlands, for example, found that of two thousand people who were exhaustively interviewed, only one even came close to meeting the criteria for clinical depression. But in modern, industrialized cultures – such as the present-day United States – about three hundred or so people out of every two thousand suffer from clinical depression.

In my last post, we talked about how the healthy, homeostatic drive generates specific emotions in us that are designed to drive behaviors that bring us into homeostasis, or equilibrium, at all levels. But with evolutionary mismatch and biochemical addiction to unnecessary survival-mode states, another, opposing drive begins to develop that acts to consistently throw us out of homeostasis, or out of balance. We have called this drive the “addictive drive,” and have suggested that it is responsible for nearly all of people’s chronic emotional pain, and also for the majority of chronic physical pain.

Fortunately, we have also found that the addictive drive can be greatly weakened, and even, with sufficient work, overcome, while the healthy, homeostatic drive can be greatly strengthened. We’ll talk about this more in upcoming posts.

 

Further reading:

Cacioppo, J. T. & Patrick, W. 2008. Loneliness. New York: Norton

Ilardi, S.S. 2009. The depression cure. Cambridge, MA: Da Capo Press 

Montgomery, J. & Ritchey, T.  2010. The Answer Model: A new path to healing.  Santa Monica, CA: TAM Books.  

John Montgomery, Ph.D., is a neuroscientist and writer. He received his Ph.D. from Caltech and has written for publications such as The Economist and The Washington Post.

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