The Evolutionary Explanation (AQA A Level Psychology): Revision Note

Evolutionary preferences for sweet, salt & fat

• Evolutionary psychology argues that human behaviour reflects the evolutionary history of the species and how  humans have dealt with adaptive problems such as avoiding predators and finding and eating the right types of food for survival

• Human ancestors survived in the environment of evolutionary adaptedness (EEA), where it was adaptive to develop preferences for foods that gave the individual the best chance of survival

• Individuals with preferences for foods that gave a better chance of survival would be more able to live to sexual maturity, reproduce and pass on the genes underlying those preferences to their offspring

• Human ancestors faced

  • unpredictable food supply

  • the threat of starvation

  • a high need to store energy

• Therefore, human ancestors’ preferred foods would be energy-dense, non-poisonous foods, such as sweet foods, fatty foods and salty foods

• Sweet foods:

  • Sweet foods such as ripe fruit contain many calories and provide an easily accessible source of energy 

  • Sweet foods are rarely poisonous, so they would be perceived as safe to eat, while sour or bitter foods may be toxic (Simmen and Hladik, 1998)

• Fatty foods

  • Foods that are high in fat are energy-dense, containing a high number of calories and releasing a lot of energy

  • Meat is high in fat and calories, allowing humans to survive the long periods that may pass between one animal kill and the next

  • Once fire was discovered, meat could be cooked or smoked to preserve it, make it easier to eat and destroy any harmful bacteria

• Salty foods

  • Salt is important for conducting nerve impulses, contracting and relaxing muscles, and maintaining the proper balance of water and minerals

  • The concentration of salt in the blood must remain at a specific level and regularly needs topping up, as small amounts of salt are lost through sweat and the action of the kidneys

• Because these preferences and avoidances aided survival, the genes underlying them were selected for and became widespread, persisting to the present day

• Evolutionary psychologists explain our current preference for sweet, fatty and salty food, such as highly-processed fast food, as an evolutionary adaptation that now has a mismatch with our environment, as we are more sedentary and have less need for energy-dense food (Krebs, 2009)

Neophobia & taste aversion

Neophobia

• Neophobia is an innate tendency to avoid new or unfamiliar foods

• Thus, neophobia has a protective function, as unknown foods could be toxic, and it is better to go hungry than to die 

• Neophobia is most pronounced in childhood, between roughly two and six years, the age at which children begin to explore their environments and may encounter foods independently of their parents' guidance about what is safe to eat

• Neophobia may lead to toddlers refusing to eat foods that are new to them in favour of the foods they are used to

• However, the neophobic reaction to new food will reduce with repeated exposure to the food once a child gets used to the taste (Birch, 1999)

Taste aversion

• Taste aversion occurs when an individual becomes ill after eating a certain food, resulting in them avoiding that food in the future because they associate it with being ill

• Taste aversion happens even if the individual knows it was not the food that made them ill, and even if they became ill only once after eating it

• Evolutionary psychologists explain taste aversion as biological preparedness (Seligman, 1971), which entails being biologically predisposed through evolution to learn through experience to avoid foodstuffs that make us ill, as this has an adaptive survival value

Research which investigates evolutionary explanations for food preferences

• Bernstein & Webster (1980) investigated taste aversion in humans and found that adults given ice cream before receiving chemotherapy developed a taste aversion to eating ice cream as they had a biological preparedness to associate their nausea with the food they had eaten rather than the chemotherapy that had actually caused the nausea

• Steiner (1977) showed that newborn babies’ facial expressions indicate pleasure over a sweet taste (upturned mouth corners) and disgust for a bitter taste (downturned mouth corners)

  • This occurs before any learning of taste preference could take place, it suggests an innate mechanism

• Knaapila et al. (2007) conducted a twin study and found that, using a standardised questionnaire to measure neophobia, the heritability of this behaviour was 67 per cent, supporting the evolutionary explanation that neophobia evolved from early humans because it protected them from eating harmful foods

Evaluation of evolutionary explanations for food preferences 

Strengths

• The fact that there is a single sweet taste receptor but around 25 bitter taste receptors suggests an evolutionarily determined need to avoid bitter-tasting toxic foods

• The idea of an evolutionarily determined preference for sweet tastes is supported by cross-cultural evidence using research on the Inuit people, who, although they had never tasted sweet food before, accepted it immediately (Bell, 1973)

Limitations

• There are individual differences in taste sensitivity, e.g., Drewnowski et al. (2001) found that some people cannot detect the bitter compound PROP, and this insensitivity appears to be inherited

  • This is hard to explain evolutionarily, although insensitivity may itself have been adaptive if it gave access to bitter foods containing anti-carcinogenic compounds

• Evolutionary explanations for food preferences, neophobia and taste aversion cannot explain cultural differences in food preferences and avoidance

Issues & Debates

• Evolutionary explanations exemplify the nature side of the nature vs nurture debate, as food preferences (e.g. for sweetness or aversions) are seen as innate and biologically hardwired adaptations from the EEA

  • However, this ignores the role of nurture, such as cultural influences and learned experiences, which shape food preferences today

• The theory is biologically deterministic, suggesting our eating behaviours are fixed by evolutionary pressures

  • This leaves little room for personal agency or conscious decision-making in eating behaviour

  • If people believe their behaviour is hardwired, they may feel less motivated to change unhealthy eating habits, thinking it’s "natural" rather than something they can consciously alter