Evolutionary Explanations for Food Preferences

• 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

• 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)

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

• 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

• SUPPORTS
• 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

• UNDERMINES
• 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

• UNDERMINES
• 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

• SUPPORTS
• 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

• SUPPORTS
• 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

• SUPPORTS
• 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