Stress should save your life.

Stress is a survival mechanism that enables us to adapt.

The understanding of evolution is key to all branches of modern biology. The interplay between genes and the environment explains why some species have adapted to a particular environment and could not thrive somewhere else. Moreover, stress indirectly leads to adaptation. As a consequence, adapted organisms live long enough to reproduce and pass on their genes. However, competition for limited resources is a crucial condition of natural selection and eliminates species that do not adapt.

Nothing in biology makes sense except in the light of evolution.

Theodosius Dobzhansky (geneticist).

Genetics & Environment

You are a product of natural selection. However, your response to stress contributes to whether you will continue to exist (by ‘you’ I mean your genes). The link between natural selection and stress might seem distant but allow me to explain.

There are two concepts to have in mind:

  • Genes, also known as ‘replicators’, are the primary unit of selection and heredity. Regarding reproduction, genetic information duplicates and then passes onto your children. In which 50% comes from the mother and 50% from the father.
  • A vehicle is what protects the genetic information. For example, the human body, a dog’s body, a tree’s trunk and leaves or the cell membrane of a bacteria are different forms of protection to genes. Each species has evolved different vehicles to protect and pass on their genetic information. These vehicles enable species, such as humans, to live in different environments; whereas others cannot. This is why there is no kangaroos in Alaska.

How does it work?

Your parents’ genes contain the necessary instructions for your cells to produce particular proteins. These proteins will replicate some of their characteristics (e.g. height). These characteristics will form your body (i.e. the vehicle) and determine your chances of surviving, reproducing and passing on your genes in a given environment.

For instance, a bird with a fragile beak living in an environment where there are only hard-shell nuts is unlikely to thrive. Probably, stronger, larger beak birds can crack and eat those hard-shell nuts. As a result, these strong-beak birds will stay healthy and reproduce. Whereas, the fragile-beak birds will either die of hunger or adapt (e.g. eat something else). These possibilities (die or adapt) indicate there is an evolutionary pressure acting directly on the population of birds making them stressed. Researches, Grant & Grant, have reported a real example involving birds. The Galapagos finches (Geospiza magnirostris) has developed into three other species.

The bird example has a hidden message that applies to every species on the planet (including humans) and links stress with natural selection: there are limited resources available. The most critical resources are food, shelter and mating partners. The lack of resources, triggers stress (e.g. hunger) in each bird. Thus, each bird will seek new alternatives to survive by adaption (e.g. moving to a different area). Therefore, competition is a necessary condition for natural selection to exist, and stress is the body’s reaction to ensure survival.

The role of stress.

Stress is a survival mechanism characterised by “an organism’s reaction to a stressor”. Stressors shifts the organism (e.g. humans) from its optimal physiological state. There are different types of stressors:

  • A biological agent (e.g. a influenza virus).
  • A chemical agent (e.g. alcohol).
  • An environmental condition (e.g. hot weather)
  • An external stimulus (e.g. a being bullied)

A real-life example involves an adult’s average heart rate in resting-state, which is between 60-100 beats per minute. However, imagine you are walking home at night, and someone tries to attack you. What happens? Your heart rate will immediately increase. The up-regulated heart rate will ensure the delivery of oxygen to your legs, generating enough energy to start running and potentially avoiding the attack. Once you are safe at home, your body restores its stable physiological state, and you are no longer in stress. This case is a simple example of how stress works for you and enables a vehicle to pass on its replicator to the next generation. Scientists and writers often refer to this survival mechanism as the fight or flight response, a concept put forward by Walter Cannon in 1915.

However, there are ways in which stress works against you. For example, sustained psychological stress (e.g. a frustrating job) may develop into mental illnesses, such as depression and obssessive compulsive disorder. But there will be a post dedicated to psychological stress.

Key takeaways

Stress is a survival mechanism and plays a vital role in natural selection. It can literally save your life. Also, stress is essential to evolution and adaptation. Hopefully, you will begin to view human behaviour from a scientific point of view, which offers several insights to your day-to-day life. More on how stress affects emotions and rational decisions you can find here.


Dawkins, R. (2006). The selfish gene. 30th anniversary ed. Oxford ; New York: Oxford University Press.

Foley, R. A., & Lewin, R. (2013). Principles of human evolution. John Wiley & Sons.

Grant, Peter R., & Grant, B. Rosemary (2008), How and Why Species Multiply: The Radiation of Darwin’s Finches, Princeton University Press

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