Health Psychology and Behaviour Change

From Science to Practice

Katy Tapper

• Publisher: Bloomsbury Academic
• Year: 2021
• Print ISBN:
  9781137579485
• Edition: 1
• eBook ISBN:
  9781350312340
• Topic: Psychology
• Subtopic: Applied Psychology
• Index: Psychology

This textbook offers a fresh approach to health psychology through the theory and practice of behaviour change. Using an array of case studies from around the world, it discusses how we can develop and evaluate behaviour change interventions. The book encourages active engagement with contemporary discussions about health behaviours, covering areas of emerging importance such as weight stigma, vaping, nudges, vaccine hesitancy and paleo-inspired lifestyles. With a focus upon critical thinking, this book will equip students for success in their research projects and beyond. Ideal for students of Health Behaviour Change and Health Psychology, this textbook is also relevant to those taking courses in related fields such as Nursing and Public Health.

PART 1

DETERMINANTS OF HEALTH

2 Evolutionary and Historical Determinants of Health

3 Social Determinants of Health

4 Individual Determinants of Health

CHAPTER 2

EVOLUTIONARY AND HISTORICAL DETERMINANTS OF HEALTH

Chapter Outline

The Origin of our Species

Evolution

Hunter-gatherers

The Agricultural Revolution

The Epidemiological Transition

Life Today

Should We Try to Live More Like Hunter-gatherers?

Conclusions

If you’ve never heard of ‘minimalist footwear’, you may be mistaken for thinking that the shoes pictured below have come from the set of The Hobbit (Image 2.1). In fact, they are shoes designed for running, but running as though one were barefoot. Why would anyone want to run long distances (or indeed any distance) barefoot? Fans of this practice argue that we evolved to run without shoes, and that running ‘as nature intended’ improves speed, strengthens foot muscles, and reduces the risk of injuries (McDougall, 2010).

Image 2.1 Barefoot running shoes, designed to simulate the experience of running without shoes.

Credit: Katy Tapper.

The increasing popularity of barefoot running represents just one of many health trends that seek to emulate our hunter-gatherer ancestors, as a means to happier, healthier, longer lives. Whether it’s eating raw meat, going to bed at sunset, or carrying your newborn round in a sling all day, proponents of a ‘palaeo’ lifestyle eschew modern habits for what they view as a more ‘natural’ existence. The reasoning is persuasive; our species has lived as hunter-gatherers for around 300,000 years, whilst our farming-based lifestyles date back 11,000 years at most. It seems reasonable to argue that we’re best suited to a hunter-gatherer way of life. But exactly how healthy were our hunter-gatherer ancestors? What did their daily lives actually look like? And is it really fair to say that the human species has remained completely unchanged over the last 11,000 years?

In this chapter we will:

• Look at how our environment has changed over the course of our species’ existence.

• Consider how these changes have influenced our health, the threats to our health, and our health-related behaviours.

• Think about the relationship between our evolutionary history and our health today.

• Consider whether we should all be trying to live more like hunter-gatherers.

THE ORIGIN OF OUR SPECIES

Hominins – the taxonomic group consisting of modern humans, extinct human species, and all their immediate ancestors from the point of our last common ancestor with chimpanzees and bonobos.

Around 7 million years ago our ape ancestors diverged along two different evolutionary paths. Some became what we today know as chimpanzees and bonobos (pygmy chimpanzees), whilst others, hominins, started to walk upright and eventually began using simple stone tools. Figure 2.1 provides a very approximate timeline of important events in the evolution of our species. Around 300,000 years ago, our own species, Homo sapiens, appeared in Africa (Schlebusch et al., 2017). We had evolved much larger brains than our early ancestors and developed more complex tools and hunting techniques. However, it was not until 11,000 years ago that we started to farm; up until this point we lived as nomadic hunter-gatherers. Arguably then, our bodies and brains may still bear the mark of our hunter-gatherer ancestry. But how much of a mark? First it is helpful to remind ourselves of the mechanics of evolution, before looking at the lifestyles of our hunter-gatherer ancestors.

EVOLUTION

Evolution refers to a change in the frequency of a particular gene or genes in a population. This could be the result of random events, for example a natural disaster that happens to wipe out all people with a particular characteristic. Alternatively, evolution could be the result of natural selection.

How does natural selection work? In a nutshell, parents pass down some of their characteristics to their offspring via their genes. If a member of a species survives long enough to reproduce, their characteristics will be more likely to be passed on to subsequent generations. Likewise, if a member of a species has more offspring (and these offspring also survive to reproduce) then these characteristics will be more likely to be passed on to subsequent generations. So any characteristic that helps an organism survive and reproduce will be more likely to occur in later generations and, over time, will become more prevalent in the population. Characteristics that work against survival and reproduction will become less common in a population.

How do new characteristics emerge within a population? Sometimes, when genes are copied from parent to offspring, errors (‘mutations’) occur. This introduces additional genetic variability into the population. Again, if the characteristics associated with these new genes promote survival and reproduction, they will become more prevalent within the population, if they work against survival and reproduction, they are likely to disappear.

Figure 2.1 The evolution of Homo sapiens

Notes: The top panel shows how we share our evolutionary ancestry with bonobos and chimps.
The bottom panel shows how our species has changed over the last 300,000 years.
Note that both panels are highly simplified – in particular, the human line in the top panel also includes many other branches of extinct species not shown.

In this way, over subsequent generations, the characteristics of a population will change so that it becomes better adapted to the environment it lives in. For example, if fruit is an important source of calories and nutrients for a particular population, but only tall people can reach the fruit from the local fruit trees, the population may gradually become taller over time.

However, a key point to remember is that a population’s environment is also changing. In the example above, if the climate gets hotter and all the fruit trees die out, being tall may now be a disadvantage because tall people generally need more calories to survive than their shorter counterparts. And our environment is continually changing. Not only do we have ice ages and temperate periods, but populations migrate. People move from the hot savannah to the cool forest. Or they set out in boats to colonise new islands. So there has never been a point in history in which one could claim that humans were perfectly adapted to their environment. Since the environment is always changing, species are always evolving.

HUNTER-GATHERERS

Hunter-gatherer lifestyle

Although our environment is in constant flux, the rate of these changes varies. Rapid environmental change can represent a challenge to a species because evolution via natural selection is relatively slow, especially for species with long lifespans. As noted above, humans switched from nomadic to settled lifestyles around 11,000 years ago. This switch can be seen as a rapid environmental change; although it may sound like a long time, 11,000 years is actually quite short in evolutionary terms. This raises the question of whether we may still be better adapted to a nomadic lifestyle rather than our modern settled one. Looking at how our hunter-gatherer ancestors lived could therefore give us an indication of what might be a ‘healthy’ lifestyle; in other words, the type of lifestyle our bodies may be best adapted for.

We can draw on four main sources of evidence to try to figure out how our hunter-gatherer ancestors might have lived:

• We can look at the few remaining contemporary hunter-gatherer groups, for example the Hadza nomads of Tanzania, the Kalahari Bushmen of Southern Africa, or the Aché of South America.

• We can examine fossil records, both of people themselves, and of nearby deposits such as faeces, and also plant remains on teeth and tools.

• We can look at our closest relatives, chimpanzees and bonobos.

• More recently, we have been able to test hypotheses about natural selection by examining our own genes.

These different methods are not without limitations. For example, fossilised evidence is scarce and not necessarily representative of a whole group of hunter-gatherers. Likewise, the lifestyles of contemporary hunter-gatherers are unlikely to have remained completely unchanged over the last ten millennia. Nevertheless, we can still use these different sources of evidence to make inferences about how our ancestors might have lived (Zuk, 2013).

Diet

Palaeolithic – the period in history characterised by hominins’ use of primitive stone tools. It extends from 2.6 million years ago to around 10,000 years ago. Sometimes referred to as ‘the Stone Age’.

What did hunter-gatherers eat? It would be a mistake to think that we could identify a ‘typical’ hunter-gatherer or ‘Palaeolithic’ diet. The diets of hunter-gatherers would have varied with both time and place (Milton, 2000). For example, among contemporary hunter-gatherers, the Arctic Eskimos eat a diet that primarily consists of marine mammals (Ho et al., 1972), whilst the Australian aborigines of the Western Desert rely mostly on wild plants (Gould, 1980). Indeed, the success of the human species is believed to be due, in a large part, to its versatility when it comes to food. Being able to find food in a range of different environments would have allowed our ancestors to exploit the different types of habitat found in Africa, and to survive the major changes in climate that took place during hominin evolution (Ungar et al., 2006; Vrba et al., 1995). Arguably, it is our ability to thrive by eating a range of different diets that is one of the hallmarks of our species.

It is also fair to say that there is a great deal we don’t know about our ancestors’ diets, and probably never will (Ungar, 2007). Foods perish and will often leave no trace in the fossil record. Even where we do have fossil evidence, in many instances it is so limited it would be unwise to accept it as representative of an entire species. Since we don’t have access to a time machine, there are many details of our ancestors’ lives that may forever remain a mystery. However, some things we can be certain of – all plant foods eaten would have been wild rather than cultivated varieties, and any meat eaten would have come from game rather than domesticated animals. From these two details, we can make a number of additional assumptions.

In particular, the wild plant foods that were eaten would have been quite different from what we find on our supermarket shelves today. For example, a wild banana contains lots of large, hard black seeds, whilst a wild avocado contains one very large stone, surrounded by a rather disappointingly thin la...

Table of contents

• List of Figures and Images
• List of Tables
• List of Boxes
• Preface
• Acknowledgements
• Introduction
• Part 1: Determinants of Health
• Part 2: Theories of Health Behaviour
• Part 3: Behaviour Change in Practice
• References
• Index