2.  You will be able to:  Understand the evolutionary explanation of food preferences  Evaluate the evolutionary theory of food preferences

3. Outline and evaluate evolutionary explanations of food preference. (4 marks + 16 marks)

4.  Our feeding system is designed to identify the things we need and to reject things we either do not need or that might be dangerous such as toxins (poisons).

5.  During evolution we have evolved a digestive system suited to breaking down these foodstuffs into the nutrients we need so they can be absorbed into the bloodstream and metabolised by the body.  Our taste sensitivities are still influenced by our evolutionary past:

6.  Sweet – allows us to identify foods rich in carbohydrates such as sugars – a key source of energy

7.  Sour – identifies food that has gone off and may contain harmful bacteria

8.  Salt – critical to the normal functioning of cells in the body

9.  Bitter – associated with plant chemicals that might be harmful

10.  Umami – discovered relatively recently and represents a meaty or savoury quality indicating a good source of protein.

11.  The ability to distinguish between these tastes is adaptive as it is important for survival.

12.  Babies and young children show a range of taste preferences. In some cases this is very narrow.

13.  Some of their dislikes are understandable; some vegetables such as broccoli and Brussels sprouts contain chemicals that can be toxic to the very young (Nesse and Williams, 1994).

14.  Babies can identify and distinguish between foods from an early age. They like sweet tastes. Furthermore, sweet foods are effective in reducing distress in babies (Benton, 2002). This suggests an innate (genetic) preference, possibly with adaptive purposes.

15.  In adults taste preferences settle down and stay fairly constant with the exception of women in the early stages of pregnancy.

16.  Morning sickness is found in at least 75% of women and has a convincing evolutionary explanation – the embryo protection hypothesis (Profet, 1992).

17.  Surveys show consistently that the foods most avoided by pregnant women are coffee, tea, meat, alcohol, eggs and vegetables (Buss, 2008).

18.  Morning sickness is most severe in the early weeks of pregnancy, when the baby’s major body organs are developing and the baby is most vulnerable. Usually it then eases off and disappears as the baby becomes fully formed.

19.  Alcohol and coffee and tea (which contain caffeine) can damage the baby’s major organs. Meat and eggs are common sources of toxins such as bacteria, while some vegetables contain toxic chemicals harmful to the developing foetus. 

20.  The sickness reaction therefore helps the mother to avoid foods that may be harmful, while vomiting prevents any toxins entering the mother’s bloodstream and affecting her baby.

21.  Food neophobia is another evolutionary aspect of food preferences. Neophobia means ‘fear of the new’. Animals have a powerful tendency to avoid foods they have not come across before.

22.  Although this can lead to a dull diet, it means that we always eat food that we know is safe and avoid new foods that may be harmful. An aspect of neophobia is that we tend to show greater liking for foods as they become more familiar.

23.  Food preferences in babies, children and non-human animals are evidence for neophobia and the evolutionary advantage of eating food we know is safe.

24.  Birch (1999) notes that neophobia is less noticeable in very young children just beginning to eat solid food.

25.  Possibly because food is selected by the caregiver.

26.  As children become more independent and able to select food, they become more cautious about eating unfamiliar things.

27.  We are very quick to learn to avoid certain foods once they have made us ill

28.  Rusiniak and Brett (1977) made wolves sick with contaminated lamb’s meat and the wolves then left sheep alone.

29.  Rats were poisoned while eating familiar and unfamiliar food at the same time. The poison could have come from either food, but

30.  The rats avoided the unfamiliar food after the sickness episode as previous experience suggested that the familiar food was ok.

31.  Humans are omnivores and are specialised to eat meat as well as fruits, nuts and plants.

32.  Humans developed to eat meat about 6 million years ago  Meat is a rich source of protein and this change in diet allowed the development of a larger brain, basic to the success of humans.

33.  The shift to meat eating helps to explain the selective pressure on brain evolution in order to cope with new technical and social skills.

34.  Fossil evidence on changes to our digestive system supports hypotheses on the evolution of meat eating and the shift to hunter-gatherer society. However, there is a limited amount of fossil evidence, and evolutionary explanations are often speculative.

35.  Through evolution, other distinctive eating behaviours have emerged:  Spices such as onions and garlic are used in cooking, especially in hot countries where food goes off quickly. Spices contain chemicals that kill bacteria, so protect people from poisoning.

36.  Biological explanations of eating behaviour especially the evolutionary approach ignore the cultural and social changes in food availability and choice over the years of human evolution. Although eating behaviour has a biological and therefore ‘nature’ element’ it is also heavily influenced by environmental ‘nurture’ factors.