A Biological Anthropologist's Analysis of Nutrition

A year or so ago I did a powerpoint presentation for a nutrition lab on how past diets are generally reconstructed. I am by no means an expert on the topic (I focused much more on evolutionary genetics and biochemistry in my coursework than bio-archaeology) but here's a brief overview:

Primatology -

• Insectivores – frugivores – folivores – exudates – omnivores – seasonality of food – group dynamics
• 96% shared base pair sequences between humans/chimps
• Human brain 3x larger than chimpanzees – consumes about 25% of our calories -  
• Terrestrial – bipedal – energy expenditure
• Kleiber's Law – Expensive Tissue Hypothesis
• Hindgut/Foregut Fermentation – larger colons, smaller intestines
• comparative anatomy

Archaeology -

• Weapon usage – different for different species – points toward hunting habits
• Cooking tools – conjectured usage from structure – granules of food particles left -
• Coprolites – fossilized feces – place in trisodium phosphate for 72 hrs – turns dark brown/black if it's human – point to extreme dietary diversity, high fiber diets – H. Erectus oldest found: shows charcoal, mollusk shell fragments, and sand grains.  
• Paleontologists rectify climate, ecology and chemical techniques to reconstruct the potential diet of the individual species  

Isotopes -

• C3/C4 Plants – Plant evolution, rubisco, efficient in drier climates  – C3 wild plants in temperate regions, C4 domesticated grains, sugar – carbon isotopes 12/13 reflected in bone collagen/apatites – bones show average, enamel shows at time of formation
• Nitrogen 15 – amount in bones reflects animal protein in diet – can skew past diets if individuals found were in differing societal hierarchies
• Sr:Ca ratio – high Sr = veg, low Sr =carn
• Otzi's Hair - last meal showed deer meat consumption and potentially cereal grains (fun fact: he had tattoos)

Bones -

• Electron microscope images of mammalian long bones – cuts made by stone tools incised above carnivorous teeth marks – evidence for scavaging - believed that food parts like scavenged marrow constituted large part of initial animal food consumption
• Markings/Scrapings/Burnings
• Diseases – Osteoarthritis, Osteoperosis, cribra orbitalia and porotic hyperostosis
• Harris Lines – growth stunts, mineralization continues 

Dental Morphology -

• Humans have two incisors, one canine, two premolars, 3 molars
• Generalized use – good for shearing, grinding, shewing – ability to chew leaves , seeds, meats, etc
• Less dimorphism
• Humans have thick enamel – tricky – thin enamel wears to make gradient for shearing with dentin 
• Past dental wear/caries -food trapped within
• high crowns and high cusp relief with shearing crests are thereby well-suited for eating tough foods like leaves and stems
• Pet Peeve Alert: Though I don't believe vegetarianism is the 'ideal' human diet, pointing at canines and asking why we have them just makes you look dumb. Lots of largely vegetarian animals have canines - horses, hippos. Chimpanzees are have huge canines but are largely non-meat eaters besides the occasional colobus monkey. Canines are largely dimorphic and have more of a role in sexual competition.

Physical and Chemical Techniques used to Analyze Diet

• Light-microscope wear patterns
• Macrobotanical remains – large fragments of preserved vegetal material
• Microbotanical remains – phytol
• Phytoliths – silica bodies that form in the cellular system of plants that remain in dental caries, cooking pots – last meal effect, indicative of last meal eaten, not necessarily normal diet
• Pollen grains     
• Protein, fatty acid, DNA residues
• Plant impression on fired clay, pot sherds, floor, etc
• Pyrolysis gas-chromatography-mass spectrometry of plant microfossils
• Electron Spin Resonance – tests highest temperature a material have been cooked at and duration of heating