The Evolution of Human Dietary Behaviour

General primate diet
- generalist, omnivorous: herbivory, frugivory, minimal carnivory (usu. of insects)
- the tarsier is the only totally carnivorous primate: living entirely off of insects

In comparison to many other mammals, primates are adapted to be sustained by a diet of relatively high quality foods. But there is still a continuum even within primates:
- from low quality, high volume diets
-- where the nutritive challenges include the abundance of phytochemicals (chemical compounds naturally occurring in plants but are not nutritive) and structural carbohydrates (e.g. cellulose and lignin)
-- of course the digestive physiology adapts to the diet; for example, the colobus monkey's stomach has an extra lobe: alkaline forestomach contains cellulolytic bacteria
- to high quality, low volume diets consisting of nutrient dense insects and fruit, which are required for shorter digestive systems (GI tracts) and fewer mechanisms to break down fibrous foods as demonstrated by the vervet monkey
-- and nutritive challenges to this lifestyle includes seasonality of food abundance and patchy distribution leading to high energy expenditure

Human Digestive Physiology
- relatively small digestive tract overall but with relatively large small intestine (that is 56% of total tract, compared to 14-29% in other apes)
- the facts of the size relativity suggests that the human gut is adapted to rich, high quality (readily digestible) foods, while other apes, mostly herbivores, have great large intestines and short small intestines due to the need for space to break down cellulose
- strong correlation between HQ-LV diet and high brain size:body weight ratio because high quality diet allows for great energy for neural development, increasing cognitive abilities and better understanding of food acquisition, which then further allows for diet quality to increase

Early hominids had relatively high brain size:body weight ratio
- Homo hablis (2.1 - 1.7 mya) 509-810ml
- Homo erectus (1.8-0.2 mya) 750-1250ml
- modern humans (100kya - present) avg. 1350ml
- hallmarks of human evolutionary theory: expansion of brain and reduction of dentition

Human Nutrition

Protein - building blocks
- tissue production and maintenance
- made of amino acids: there are 20 types, and only 10 can be produced by the human body while the remaining 10 must be acquired through the diet because failure to do so results in degradation of the body's proteins (e.g. muscles) in order to obtain all required amino acids

Carbohydrates - energy source for bodily functions
- immediate energy needs met first and excess  is converted and stored as fat
- dietary sources: simple (sugars) and complex (starches)

Vitamins - necessary for bodily functions
- malnutrition: deficiency of niacin leads to pellagra, while deficiency of vitamin C leads to scurvy
- there are two kinds of vitamins: water soluble and fat soluble
- water soluble vitamins need to be replenished daily as they dissolve in water and excess/unused amounts are flushed out through urine, e.g. B-complex vitamins and vitamin C
- fat soluble vitamins can be stored in fat and liver cells and overdose is possible (e.g. pregnant women are advised against eating liver for obtaining high amounts of vitamin A correlates with birth defects)

Minerals - inorganic elements
- found in rocks and soil, absorbed by plants as they grow and through these plants we obtain minerals
- without minerals the body would be unable to:
-- build new tissues
-- contract muscles
-- process nerve reactions
-- clot blood
-- keep your body pH neutral
-- regulate body processes
-- release energy from food

Dihydrogen monoxide - humans are 60-75% water and it is important for:
- transporting nutrients
- lubrication
- shock absorbers in joints
- medium of metabolism
- regulation of body temperature

Taste

Flavour is a combination of taste, smell, texture, sight and physical characteristics. A sense of taste is neurological feedback on chemical properties of a substance. Prior to ingestion, it is a screening process to check whether the food is edible, ripe, or toxic. This ability for taste is adaptive.

Are taste preferences linked to food selection?
- both sweet and salty are innate/natural and universal
- there is widespread dislike for bitter and sour flavours
- umami is universal but not well-known

Universal elements of human relationship with food
- omnivorous diets
- foodstuffs may require preparation (e.g. nuts cracked, animals killed) (even before cooking) in order to transform it into being truly edible
- elaborate food system, including social taboos on top of personal preferences

Biocultural evolution of food systems
"Interrelationship of biological and social forces in shaping human food use and nutritional status of individuals and populations." Pelto et al 2000