Evolutionary Explanations for Food Preferences

Evolutionary explanations for food preferences, AO1 and AO2

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AO1 - Early Diets

  • Preferences for fatty food would have been adaptive for early humans, because conditions in the EEA meant that energy resources were vital to stay alive
  • Modern humans are more concerned with the nutritious value of food (i.e. that it contains vitamins, minerals, and other substances necessary for a healthy diet)
  • Instead what we eat is rich in calories but not particularly nutritious
  • In the EEA, calories were not as plentiful as they are today
  • It makes sense that humans and other animals have evolved a distinct preference for foods that are particularly rich in calories
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AO1 - Preference for Meat

  • Human ancestors began to include meat in their diets to compensate for a decline in the quality of plant foods caused by receding forests two million years ago
  • Fossil evidence from groups of hunter-gatherers suggests that their daily diet was derived primarily from animal-based foods
  • In particular animals organs such as liver, kidneys and brains, that are extremely rich sources of energy
  • A meat diet, full of densely packed nutrients, provided the catalyst for the growth of the brain
  • Milton: without animals, it is unlikely that early humans could have secured enough nutrition to evolve into the active and intelligent creatures we became
  • Meat supplied early humans with the essential amino acids, minerals and nutrients they required
  • This allowed them to supplement their diets with marginal, low-quality, plant-based foods that have few nutrients but lots of calories (e.g. rice and wheat)
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AO1 - Taste Aversion

Taste aversion

  • First discovered by farmers trying to rid themselves of rats
  • They found that it was difficult to kill the rats using poisoned bait, because rats would only take a small amount of any new foods
  • If they became ill, they would rapidly learn to avoid it
  • Garcia et al: discovered that rats who had been made ill through radiation shortly after eating saccharin developed an aversion to it

The adaptive advantages of taste aversion

  • Subsequent research has discovered that odour of food can also be linked to illness and consequently to the development of a food aversion
  • It would have helped our ancestors to survive, because if they survived eating something poisonous, they would not make the same mistake again
  • It can still be acquired up to 24 hours after the consumption of food, as the reaction to poisoned food in the natural environment is often delayed
  • Once learned, such aversions are very hard to shift - an adaptive quality designed to keep our ancestors alive
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AO1 - The Medicine Effect

  • There is also evidence that animals can learn a preference that makes them healthier, with any food eaten just before recovery from illness being preferred in the future
  • Garcia et al: when a distinctive flavour is presented to a thiamine-deficient rat followed by an injection of thiamine, it acquired a preference for that flavour
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AO2 - The Importance of Calories in Early Diets

  • Gibson and Wardle: carried out an experiment with four- and five-year-olds
  • The best way to predict which fruit and vegetables they picked was not how sweet, or how familiar, or how protein-filled they were...
  • ...it was how calorie-dense
  • Bananas and potatoes, which are very calorie-rich, were more likely to be chosen
  • This demonstrates an evolved preference for calorie-rich foods
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AO2 - Could Early Humans Have Been Vegetarian?

  • Cordain et al: argued that early humans consumed most of their calories from sources other than saturated animal fats
  • This has led to the suggestion that our distant ancestors were healthy eaters and may have been vegetarians
  • HOWEVER, Abrams: all human societies display a preference for animal foods and fats
  • It also would have been impossible for humans to be completely vegetarian, because they would not have been able to get sufficient calories from plants and grains
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AO2 - Are All Food Preferences a Product of Evolut

  • Food preferences cannot all be traced back to the adaptive pressures of the EEA
  • A beneficial trait today, e.g. the consumption of low cholesterol foods, would not have evolved because of its beneficial traits for our ancestors
  • Many things important to our ancestors, such as saturated animal fats, are harmful in modern environments, so we are more likely to avoid them to lead a healthy life
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AO2 - Taste Aversion: Biological Preparedness

  • Seligman: claimed that different species evolved different learning abilities
  • This natural selection of differential learning has occurred so that each species has the ability to learn certain associations more easily than others
  • Especially those that help them survive
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AO2 - Taste Aversion: Applications of Research

  • Can be helpful in understanding the food avoidance that can sometimes occur during the treatment of cancer
  • Radiation and chemotheraphy can cause gastrointestinal illness
  • When this illness is paired with food consumption, taste aversions can result
  • Bernstein and Webster: gave patients a novel-tasting ice cream prior to their chemotherapy, and the patients developed an aversion to it
  • This has resulted in the development of the 'scapegoat technique'
  • It is consistent with the adaptive avoidance of novel foods, a.k.a. neophobia
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IDA - Testing Evolutionary Hypotheses

  • A common way of testing evolutionary hypotheses is through comparison with a different species
  • Although we cannot travel back to the EEA to see what adaptive problems faced our ancestors, we can study a related species (e.g. chimpanzees) who face these today
  • We can also look for modern-day products that reflect our evolved food preferences
  • Pizzas, burgers and sugary foods sell well because they correspond to and exploit our evolved desires for fat and sugar
  • HOWEVER this does ignore more proximate causes, like advertising, availability and laziness
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