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The evolution of our primal heart

Evolutionary principles have been applied mainly to understand the human body, not our mind. But in the last couple of decades a flood of research from the new field called evolutionary psychology reveals that our emotional nature is the product of the same evolutionary forces that have shaped our body.

Three such forces are key.

The first are our genes, our body’s architect and construction manager. At the moment of conception our DNA contains the code that will design and build our body, as well as key features of our mind and emotions. Genes first appeared in primitive bacteria four billion years ago, but DNA is changeable and constantly reinvents itself through spontaneous mutations or the card shuffle of sexual reproduction.

If such changes foster survival, the bacteria, plant, or animal will reproduce and the genes will spread; if the changes undermine survival the organism will die and the genes will disappear. This process is called natural selection, and it is the second key component of evolution.

The third force is the environment in which the genes evolve. Our planet’s ecology has been in a constant state of flux. Climate changes, for instance, can either wipe out genes that thrived in the old habitat or promote their survival. Fortunately for everything alive today, the dance of change between genes and ecology sustained a four billion year chain of increasingly complex life that ultimately produced the extraordinary code of human DNA.

A common illustration of human physical evolution describes how environmental changes transformed knuckle-dragging African apes into upright beings which could run fast and for long distances. Apes are mostly creatures of the jungle. They need four strong limbs that can grip branches to swing from tree to tree in the nutrient-dense forest. Roughly five million years ago climate change cleared many of the jungles of Africa and replaced them with grasslands where foods are abundant but widely dispersed. As a result of mutation and sexual reproduction some new primate genes appeared that enabled running on two legs. In the jungle these genes offered no survival advantage and quickly died out. But for apes next to the savannah, two-legged running provided enormous foraging advantages. The highly mobile beings could leave the jungle entirely and spread far and wide into the savannah which was rich in nuts, tubers and herds of animals.

​Thus emerged the first members of a new primate genus called Homo (Latin for “human”). Over time dozens of species of that genus appeared and disappeared. Only one species, Homo sapiens (“wise human”), ultimately survived, appearing on the savannah about 200,000 - 300,000 years ago. They survived there for another 200,000 years, until about 60,000 years ago, when Homo sapiens first left Africa to spread across the globe. Those pre-modern humans were anatomically the same as we are today, with all our distinctly human features, such as our big brains and dexterous fingers.

​The hunter-gatherer lifestyle persisted all over the world until about 10,000 years ago when the invention of agriculture gradually replaced it. Evolution is a very slow process, and the many millennia since our species left Africa is too brief to bring about any significant change to the deep structure of the human genome. Only superficial traits such as racial features have evolved into specific sub-populations. But the core of our genome is the same as it was eons ago on the primal grasslands.

The idea that universal human traits are related to the Paleolithic world of ancient foragers is relatively modern. Although Darwin set out his theory of evolution 150 years ago, sufficient archeological and biological evidence demonstrating the correspondence between human traits and the lifestyle of African hunter-gatherer nomads was not available until about a century later. Physical traits were the most obvious and were the first to be identified as a product of the savannah lifestyle. In more recent times a wealth of evidence enables scientists to attribute very specific physical features of our body to our time on the grasslands. These include distinctive muscles in the foot, leg and butt that enable long-distance running, crucial for hunting big game in the grasslands. We can thank our modern ability to run marathons to our ancient foraging way of life.

​Our focus is not the evolution of our anatomy, but rather that of our emotions. However that word refers to a vast swath of human experience and our mission is more specific. Our spotlight is aimed at a key part of every emotional experience – its subjective feel – that is often ignored both in our daily life and in scientific research. The term for the inner flow of feeling is the noun affect, pronounced with the accent on the first letter, unlike the identically spelled verb with the accent on the last syllable. 1 (The number references a note which appears below.)

Affect is the primary ingredient of all emotional experience. It consists of the sense of whether we feel positive or negative (which psychologists call valence) and how calm or agitated (called arousal). Studies suggest that affect is universal; all known languages have a word for “I feel good” and “I feel bad”. Research also shows that our affect is the bedrock of all emotion. We build more complex emotional states, such as joy and sadness, on the foundation of feelings of good and bad.2 So affect critically affects our happiness. You can’t build that uplifted feeling on a base of negative affect. Only the root of positive affect can produce happy feelings.

It turns out that the affect that everyone feels has been heavily influenced by evolution. Through the process I will now describe, everyone is born with roughly the same affective biases, a set of likes and dislikes, which cause us to react positively to a relatively small set of generic experiences, such as eating and sex, and negatively to others, such as having no food for days or being socially shunned. Those universal affective biases I call our primal heart.

Affective evolution refers to the process by which natural selection shaped our genes and mental systems to create those affective biases. Consider how evolutionary forces would program into the human genome a universal set of such likes and dislikes.3

Like all other genes, those that govern the human emotional system are constantly mutating, and new genes appear with the birth of every individual. For example, eons ago, some individuals on the savannah were born with genes that caused them to enjoy the kinesthetic sensations of walking; they felt good during their long rambles on the grasslands. Other individuals were born with genes that disliked trekking the wilds.

​In a nomadic culture, hiking long distances is critical for survival. The affective genes of the hiking enthusiasts provided them with a survival advantage over the primal couch-potatoes. The hiking enthusiasts were more likely to find food and water. Over long periods of time during which people needed to continually move to survive, the pro-hiking genes will proliferate, while those of loafers will die out. In time, virtually the entire species will acquire the survival-promoting affective genes. The lazy genes might randomly appear over time, but will just as often disappear.

​Consider another example. We know from paleontology and anthropology that nomads could live no more than a few days without the support of their band of 20-40 people. Alone in the vast open range they would be easy pickings for hungry predators like lions. They could not keep a fire going night after night. Nobody would protect them if they hurt themselves. Survival on the African savannah requires a small tightly bonded community of people who will put their lives on the line for each other. Nomads born with the genes of hermits, and who avoided the company of others, would not live long. Hunter-gatherers who loved social intimacy would survive and reproduce. Over time everyone in the tribe would acquire the latter’s genes.

Evolution imprinted a range of innate affective preferences that caused our ancestors to feel especially good when they performed the survival-critical behaviors required by their hunter gatherer environment. And to feel bad when they behaved in ways that threatened their nomadic survival, such as playing with snakes, not eating or failing to make any friends.

The surprising result is that the affective genes in every human alive today are stuck in the past. Your affective system is, in effect, a time capsule. It is designed for a hunter gatherer world that is radically different from the environment of modern cities that most of us occupy now. 4

Some primal attractions, such as eating and sex, are easily identified. Other primal preferences are not nearly as apparent in a modern world that is radically different from the one in which our genes evolved. To identify them you need a basic knowledge of ancestral human life.

Yet most of us know almost nothing about this crucial era. While schools, universities, and the media give much attention to human history as far back as thousands of years ago, they mostly ignore the vastly longer period of prehistory that germinated the core elements of human nature.5 So we need to educate ourselves about the primal era to understand experiences that our genes like and dislike. A major part of my work is to describe the basic features of the nomadic lifestyle.

I think the best introduction to our primal past is a paper by evolutionary psychologist Peter Gray.6 He examines the scientific record of the many hunter gatherer cultures that survived up to the modern era (now mostly gone) and shows how they all had common elements, making them an important source to understand life in the ancestral era. See also a classic essay by Marshall Sahlins, one of the early experts on primal culture, which is aptly named: Hunter-gatherers: insights from a golden affluent age.7 There are several popular book-length investigations of the hunter gatherer lifestyle, many of which are highly readable, such as The Old Way, Nisa, and Coming Home to the Pleistocene.8 There are many scholarly books on the subject as well.9

Another knowledge base that can help identify our primal preferences is the science known as positive psychology. The main tool of that field is a demographic survey; researchers ask questions of large numbers of people to determine what makes them feel good or bad. Thousands of such studies from all over the world have determined the experiences that most arouse our emotions. Those experiences turn out to be exactly the modern versions of the things that helped or hindered our ancestors’ survival eons ago. For example, the two behaviors discussed above that are essential for the survival of hunter gatherers, movement and deep social connections, are high on the list of experiences that almost all people report that they value highly. Eating and sex obviously are too.

Note the dovetail between evolutionary psychology and positive psychology. What the former identifies as key to our wellbeing based on basic principles of affective evolution, the latter confirms through surveys of real people alive today. Because of the dearth of much cross-disciplinary work on emotions, few people have noticed the harmony of the two fields in the way I have just illustrated.

And there is a third field of science which in turn dovetails with the other two: medical research. Anything touted as a primal preference must also promote our physical health. What pleases our affective genes must also please our physical genes. Why?

Both our physical and affective genes were shaped by the same force, evolution, because they produced the same result, survival. A genetic inconsistency between what we need to feel good and what we need to be physically healthy and would impair survival and quickly disappear from the gene pool. The experience that make us physically healthy align with those that promote emotional wellbeing. Hence happiness experts Rick Foster and Greg Hicks, who have studied the happiest people all over the world, report that “happiness and health are one”.10 Evidence that something enhances our health is a clue that it also boosts our happiness.

Modern health research can help us identify some features of our primal heart that the other disciplines might overlook. Medical science has an advantage over psychological surveys: it uses objective quantitative evidence like blood pressure, cortisol levels, and longevity to measure outcomes rather than the subjective reports of a person’s affective state.

For example, research has discovered the previously unidentified health benefits of contact with nature. Patients in hospitals who face a park recover faster than those who face warehouses! Spending time in a forest can have measureable health benefits after just a few hours! Most of us intuitively know that nature contact feels good. But now we can use health science to support that intuition. Our nature is to be happy in nature!

In fact, we appear to innately value one type of natural environment more than any other. Can you guess what that would be?

Scientists have surveyed children around the world to determine which type of natural landscape they like the most. They choose children for this study because youngsters are too young to become attached to the environment they happen to occupy. The children were shown photos of a tropical forest, deciduous forest, coniferous forest, desert, and the African savannah. By a large measure, the children preferred the savannah. Even more amazingly, they tended to prefer the tree shapes of the ancestral location, like Acacia trees which have a crown as broad as the trunk, as opposed to tall slender trees with dense or skimpy canopies. Deep in the cells of our modern bodies are primal preferences for our African homeland!11

​The foregoing provides the background for a method to identify the nature of our primal heart: 1) determine the key survival essentials of the human evolutionary environment (such as movement and social connection); 2) look to positive psychology to verify that those behaviors are widely enjoyed; and 3) seek further confirmation in health research that shows that those activities enhance our physical health. I use this method to identify the approximately two dozen experiences that provide us the greatest joy. Once you know what they are, you can start to consciously bring them into your life and experience a happiness boost.


1 See How Emotions Are Made: The Secret Life of the Brain, Lisa Feldman Barrett, 2017, p. 72 for a detailed discussion of affect. As Barret points out (p.376 note 36 )“Scholars and scientists have confused emotion and affect for centuries. See In the science of emotion the term “affect” is sometimes used to mean anything emotional. In this book we limit the term to a specific meaning: a change in your internal environment that you experience as feelings of valence and arousal. This modern conception of affect was developed by Wilhelm Wundt: see” I was “affect” in that modern, specific way too.

2 See Ibid., Chapter 4, “The Origin of Feeling”

3 In this sentence I state: “evolution programmed into the human genome a set of likes and dislikes…” Genes, of course, don’t have likes and dislikes; only our emotional system has that. The phrase is shorthand for the statement: “evolution programmed a set of genes which trigger the emotional system to respond with a set of likes and dislikes…” For the sake of brevity, throughout the book I make similar statements, such as “our genes enjoy” or “our genes are attracted”; please read them as similar shorthand.

4 “Evolutionary psychology: a primer”, Leda Cosmides, John Tooby, University of California Santa Barbara,, accessed April 18, 2014. “The evolution of happiness”, David Buss, 2000, American Psychologist, Vol 55(1) pp.15-23.

5 The Story of B, Daniel Quinn, 1997, pp. 244-6.

6 "Play as a foundation for hunter-gatherer social existence", Peter Gray, 2009, American Journal of Play, 1, pp.476-522.

7 Published in the Pacific Ecologist, Winter 2009.

8 The Old Way: A Story of the First People, Elizabeth Marshall Thomas, 2007; Nisa: The Life and Words of a !Kung Woman, Marjorie Shostak, 2000; Coming Home to the Pleistocene, Paul Shepard, Florence R. Shepard, 2004.

9 Such as: The !Kung San: Men, Women and Work in a Foraging Society, Richard Lee, 1979; and The Cambridge Encyclopedia of Hunters and Gatherers, Richard Lee, Richard Daly, 2004.

10 How We Choose to Be Happy: The 9 Choices of Extremely Happy People--Their Secrets, Their Stories, Rick Foster and Greg Hicks, 2004, p.5.

11 “Evolved responses to landscapes”, G. Orians, J Heerwagen, (1992), Chapter 15 in The Adapted Mind: Evolutionary Psychology And The Generation Of Culture, Jerome H Barkow, Leda Cosmides, John Tooby (Eds).


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