Outline and evaluate evolutionary explanations for food preferences.

Salt is also key for animals as high sodium concentrations maintain the body’s nerve and muscle activity and water balance. Dudley et al (2008) found that ants prefer salty snacks to sugary ones in inland areas that tend to be salt poor. Ants were tested from varying distances from the ocean for taste preference. It was found that ants that lived 60 miles inland preferred a 1% salt solution to a sugar solution ten times more concentrated. Carnivorous ants did not exhibit this difference as they receive sufficient salt from their prey. Dudley et al concluded that salt preferences of inland ants are seen as an adaptive response to maintain competitiveness. Researchers believe this may be true for all animals including humans. One weakness of Dudley et al’s research is that it was conducted on animals. Animals are very different to humans and therefore the findings cannot be generalised to the human population. However, it is clear that salt is important in both human and animal diets.

Foods that are either bitter or sour are not preferential foods for humans as the evolutionary theory suggests they are associated with poison and thus there is a tendency to avoid them. The ability to distinguish bitter tastes is developed as an evolutionary mechanism to protect early humans from eating poisonous plants. Plants are more likely than animals to contain toxins because they produce a variety of toxic compounds in order to protect themselves from being eaten. Herbivores have fewer bitter taste genes than omnivores or carnivores because avoiding bitter plants would considerably limit their food sources. Now humans have evolved bitter and sour foods are more palatable but not so much so to children. It has been found that humans have 30 genes that code for bitter taste receptors. Each receptor can interact with several compounds allowing people to taste a wide variety of bitter substances. Research by Menella found that children reject bitter food due to basic biology. 900 people aged 5-50 were tested by being given bitter foods and found that children were more sensitive to bitter food than adults. It was found that the variation of a taste gene called TAS2R38 makes children sensitive to bitter tastes. There has always been an evolutionary importance of being able to detect potentially harmful foods in our diet. This is clearly illustrated by the fact that humans have 27 taste receptors for bitter tastes but only 2 for sweet. Simmen and Hladik claim this asymmetrical difference between sweet and bitter taste discrimination reflects different evolutionary trends for meeting energy requirements.

A key strength of the evolutionary explanations for food preferences is the acknowledgement of the nature and nurture debate demonstrated by research into the bitter and sour taste buds. The evolutionary theory suggests humans have evolved to suit the environment however the study of the 30 genes coding for bitter taste receptors and the 27 taste receptors demonstrates the influence of nature on food preferences. It illustrates that it is the combination of both genes and the environment that influence human food preferences.

However, a significant weakness of the evolutionary explanations for food preferences is that it ignores the influence of culture on human diets. Research into all five taste buds explains why humans have evolved in their food preferences but not why humans can have such diverse diets in different cultures. Some diets preference umami foods whilst others preference salty foods. Poland and Portugal for example have the highest salt intake in the world whilst Sweden and Finland have the lowest salt intake in the world. Sweden on the other hand preferences food with fibre as the people in their country eats the most fibre in the world. This extreme diversity in human diets between cultures suggests than the evolutionary is not a satisfactory theory in explaining human food preferences.

The evolutionary explanation also explains the taste aversion and medicine effect theories. Taste aversion is when a person finds that they may have had a very bad effect from some food that they have eaten and because of this they learn to always avoid that food now associating it with the bad experience. Seligman (1970) claimed that different species evolved different learning abilities which he called biological preparedness. This natural selection of differential learning occurred so that each species has the ability to learn certain associations more easily than others, particularly those that helps individuals survive. The medicine effect is the opposite of the taste aversion theory. It states that one can learn a particular food preference is they have had a good experience when eating it for example if a person was ill with a sore throat and they had a hot drink and their throat felt better they may believe that if they ever have a sore throat drinking that hot drink will cure it. These two theories are a key part of the evolutionary explanation for food preferences.