How the stress response of your hunter-gatherer ancestors helped them survive and why it may now be damaging your health?
Learn about how the stress response of your hunter-gatherer ancestors gave them the edge in times of danger, why your own stress response is more or less the same as theirs and why it could now be damaging your health.
We all know how it feels to be stressed. Many of us chaps associate stress with looming deadlines, job worries, financial burdens and responsibilities such as raising a child or being a carer for a relative. A recent study found that during a typical week some 76% of men experience stress and over a year a similar proportion have at some point felt so stressed that they have been overwhelmed or unable to cope.
However, have you ever questioned why you experience stress in the first place?
Stress is nothing new, it has affected you and your ancestors as well as other species for millions if not billions of years.
Assuming that Darwin was correct, it is reasonable to assume that there must be some sort of natural advantage that humans derive from stress. Otherwise, surely we would have evolved some better alternative that didn’t make us feel so bad?
The truth is that humans have evolved to thrive off stress. Ask one of your hunter-gatherer ancestors and he would probably say that stress is predominantly a good thing.
How the stress response of your hunter-gatherer ancestors helped them survive?
When exposed to a dangerous or life-threatening situation, such as being attacked by a hungry predator, nerve signals originating from sensory organs such as his eyes or ears would be sent to the brain. This would kick into play a rapid sequence of process steps activating his fight-or-flight response and giving him a much-needed boost. He would now have been ready to confront the predator or run away from it.
The nerve signals would first reach the amygdala region of his brain which helps to process emotions. If it perceived a threat, alerts would be sent to the hypothalamus region of the brain which acts like a command centre. The hypothalamus region would then communicate with the autonomic nervous system which controls involuntary processes within the body such as breathing, heartbeats and the fight-or-flight response including the production and release of hormones.
The autonomic nervous system would immediately start to release the stress response hormone adrenaline into his blood stream. This hormone would be released from the adrenal gland at the top of the kidneys, and some neurons in the central nervous system (see footnote i).
The stress response hormone adrenaline would travel through the blood, sending chemical messages across his body and instructing each part exactly how to respond to the perceived threat.
The air passageways linking his mouth and nose to his lungs called bronchiole would widen allowing his respiration rate and oxygen intake to increase. His heart would pound faster than normal, blood vessels constrict and blood pressure rise. This would mean a greater flow of blood around his body – transporting and supplying much needed oxygen and nutrients to key organs and muscles – enabling enhanced performance. For instance, higher levels of oxygen reaching the brain would increase his alertness.
Blood glucose synthesis in the liver would increase the release of glucose and fats from storage locations across his body and into his bloodstream, increasing the availability of short term energy.
His pupils would dilate, and the ciliary muscles of the eye lens would relax allowing more light to enter his eyes and enhance his central vision. At the same time, his peripheral vision and hearing abilities are likely to have been hindered.
His immune system would be put into a state of full alert to protect from any infections or trauma caused by getting bitten or mauled by the predator. Perhaps the predator had nasty bugs on its claws or in its saliva, or inflicted wounds had been exposed to dirt from the surrounding environment. This heightened state of alert is also known as inflammation.
Non-vital bodily processes such as digestion would be toned down or even switched off. For example, the flow of blood would be diverted from the digestive system by vasoconstriction focusing his body’s resources on muscles and key organs such as the lungs. This would inhibit peristalsis, one of the main process behind the digestion system. One possible physical reaction to this could be the sensation of butterflies in his stomach.
After all of this, your ancestor would be primed for fight-or-flight. He would now have more strength, energy and alertness to use in a hand fight, handle a weapon, climb a tree, run fast or run for longer distances. The physical effects of stress may well have saved his life.
As the initial surge of adrenaline petered out and whilst the threat was still present, the hypothalamus region would trigger a series of process steps involving the hypothalamic-pituitary-adrenal axis – ending with the release of cortisol from the adrenal gland. This would enable the body to maintain its fight-or-flight response and keep it on high alert.
Once the danger or threat had finally passed, the parasympathetic part of the autonomic nervous system which is associated with a more relaxed body would help dampen his body’s response to stress.
How has the stress response of modern humans changed since our hunter gatherer ancestors?
Evolution is the process by which certain heritable characteristics such as our response to stress change over successive generations. Often these slight changes are unremarkable and unnoticeable between consecutive generations and only apparent after very many.
The main mechanism for this change process is natural selection. This enables only the best adapted varieties of a species to survive and pass their genetic characteristics to succeeding generations while less well adapted varieties are more likely to be wiped out.
Our ancestors would have benefited from the boost that their male stress response gave them. As shown above, it would have given them a greater chance of surviving dangerous situations and going on to pass their genes to successive generations.
On the contrary, their mates who didn’t have such an effective stress response were more likely to have been killed and eaten by predators before having the opportunity to reproduce or support the raising of their offspring.
What's more, an effective male stress response may have made them more effective when hunting prey such as mammoths, allowing them to bring more food home to support their partner and growing families.
The overall result is that over many generations due to natural selection, the stress response more akin to that exhibited by our ancestor who survived the predator attack would have become more and more common.
You have to appreciate that evolution is a painstakingly slow process with next to nothing happening from one millennium to the next. Humans evolved over hundreds of millennia to become highly specialised hunter-gatherers. The shift away from hunter-gathering to agriculture only started ten to twelve millennia ago which is hardly any time on an evolutionary scale.
This means that even though technology and (arguably) society have gone through leaps and bounds in the last few millennia, modern men are to all extents and purposes, still hunter-gatherers living in a 21st century world.
What are the effects of stress on the body and why it may be damaging your health?
As we have shown, not all stress is bad. The physical effects of stress on the human body came to your ancestor’s rescue.
In moderation or short bursts, some stress can be appropriate or even beneficial in our modern lives. Good stress helps us get out of bed in the morning, get through difficult encounters, get excited for a first date and compete at sports. On these occasions, our bodies can quickly return to normal with no adverse impact on our health or wellbeing.
The trouble lies with situations where we are unable to find ways to relax quickly and the stress is prolonged or activated repeatedly – this is also known as chronic stress. The permanent state of the resulting fight-or-flight response without recovery periods, results in the wear and tear of our bodies, gradually impacting both our mental and physical health.
Our ancestors would have led relatively calm and stress free lives, mainly experiencing stress due to infrequent, dangerous events such as predator attacks. In these instances, stress would have been short lasting and beneficial as it kicked in their fight-or-flight response.
On the contrary, our modern lives are filled with a seemingly never-ending barrage of stress causing daily battles. These are far more frequent, potentially longer-lasting but less serious (than being eaten alive): commutes, multi-tasking, financial issues, difficult relationships, bereavements, or dealing with unreasonable bosses.
The bad news is that your body’s reaction is just the same as your ancestor who survived that predator attack all those years ago. We are putting our bodies through a permanent state of stress response which has many negative implications on both our physical and mental health.
There are many problems and stress related illnesses caused by chronic stress. In fact, chronic stress is linked to the six of the most common causes of deaths including heart disease and cancer.
Stress can cause mental health issues such as depression and anxiety, cardiovascular diseases such as heart attacks and strokes, along with chronic diseases associated with chronic inflammation such as asthma, cancers and even Alzheimer’s. Other illnesses and problems include those associated with poor sleep, low testosterone levels, poor digestion, weight gain, substance addiction and diabetes.
It is important to realise that everyone is different. Some events may cause some men to stress whilst not affecting others. Some men can handle higher levels of prolonged stress without suffering from adverse effects whereas others may be more able to train up their own internal coping mechanisms. Prior experiences, genetics and the surrounding environment may also play a part.
Stress is something that benefited our hunter-gatherer ancestors helping them survive dangerous or life threatening situations such as predator attacks and mammoth hunts.
Modern life makes men prone to experiencing more long term and sustained levels of stress. This has led to a mismatch between what is causing our stress and our body’s stress response which was originally designed to help us survive short-term threats. In other words, many of us are now living in a constant state of fending off that predator.
The trouble is the body’s response to stress – although effective in short bursts – is deadly in the longer term and is linked to a whole host of health problems.
So, stop trying to suck it all up like a man, understand that it could be a real problem, and take action now. There’s plenty that can be done to be more stress free!
Interested in finding out how stressed you are? Take our stress quiz now to find out.
(i) The autonomic nervous system comprises of the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is responsible for activating the body’s fight-or-flight response and the parasympathetic nervous system is responsible for bodily functions that typically occur when your body is feeling more relaxed. This includes involuntary activities which occur when you are resting such as salivation, digestion, urination, defecation and sexual arousal.
This article was created for informational purposes only and does not necessarily represent the views of For Chaps Ltd. It is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice. Always seek the advice of your doctor or other qualified health provider with any questions you may have regarding a medical condition.