Problems of survival (3): Diet and the omnivore’s dilemma

The human diet

I forager vs. chimp diet

I cooking

I recent evolutionary changes

Solving the omnivore’s dilemma

I sweet and bitter tastes

I learning biases: neophobia

I taste-aversion learning

I social learning

I culture (spices and cuisine)

Man the hunter?

Human forager vs. chimp diets

vert. nuts/ othermeat roots seeds fruits plant insects

Onge 79 19 0 0 0 2Anbarra 75 8 0 4 0 12Arnhem 77 19 0 0 0 3Ache 78 0 0 1 9 11Nukak 41 0 0 40 0 20Hiwi 75 15 0 5 2 3Gwi 26 37 0 37 0 0Hadza 48 30 0 15 0 0

CHIMP 2 0 5 60 29 4

Dietary percentage of foraged foods, from Kaplan et al. 2000

Human forager vs. chimp diets

(from Kaplan et al. 2000)

The advantages of cooking

Change in digestibility from cooking:

Starch source Raw Cooked % increase

Wheat 71 96 34%Oats 75 96 28%Barley 93 99 6%Green banana 49 97 96%Plantain 54 100 87%Potato 97 51 91%Pea 80 91 14%

(from Carmody and Wrangham 2009)

Recent changes: Lactase persistence

I evolved in dairy farming communities in central Europe

I first evolved about 7500 years ago

I evolved independently in Africa and Middle East

Recent changes: Amylase copy number

I amylase digests starch in saliva, varies by copy number

I more copies means more amylase

The Omnivore’s Dilemma

The human diet

I forager vs. chimp diet

I cooking

I recent evolutionary changes

The omnivore’s dilemma:

I which foods are toxic?

I which foods are most nutritious?

I how can we know?

Solving the omnivore’s dilemma: sweet and bitter tastes

I newborns react more positively to sugar solutions than water

I most infants dislike bitter and sour tastes

I around 4 months, infants develop liking for salty tastes

reaction of a two-week old baby to taste of sugar and lemon juice

Solving the omnivore’s dilemma: Neophobia

I rats are also food neophobic; eat a small amount at first

I willingness to try new foods is greatest during the first twoyears

The omnivore’s dilemma: Social learning

I young rats prefer foods mothers ate when pregnant andnursing

I young rats forage where adults are foraging

I adult rats prefer food if have smelled on breath and body ofother rats

I howler monkey infants: copy mom when eating leaves, notfruits

The omnivore’s dilemma: Social learning

I young rats prefer foods mothers ate when pregnant andnursing

I young rats forage where adults are foraging

I adult rats prefer food if have smelled on breath and body ofother rats

I howler monkey infants: copy mom when eating leaves, notfruits

The omnivore’s dilemma: Social learning

I young rats prefer foods mothers ate when pregnant andnursing

I young rats forage where adults are foraging

I adult rats prefer food if have smelled on breath and body ofother rats

I howler monkey infants: copy mom when eating leaves, notfruits

The omnivore’s dilemma: Social learning

I young rats prefer foods mothers ate when pregnant andnursing

I young rats forage where adults are foraging

I adult rats prefer food if have smelled on breath and body ofother rats

I howler monkey infants: copy mom when eating leaves, notfruits

The omnivore’s dilemma: Learning in utero

Babies’ intake of carrot-flavored cereal compared to plain cereal

(from Mennella et al. 2001)

The omnivore’s dilemma: Social learning

I human babies more likely to take novel food from mom thanstranger

I human babies more likely to take novel food from stranger ifstranger eats first

I human babies choose food eaten by actress speaking theirown vs other language

The omnivore’s dilemma: Social learning

I human babies more likely to take novel food from mom thanstranger

I human babies more likely to take novel food from stranger ifstranger eats first

I human babies choose food eaten by actress speaking theirown vs other language

The omnivore’s dilemma: Social learning

I human babies more likely to take novel food from mom thanstranger

I human babies more likely to take novel food from stranger ifstranger eats first

I human babies choose food eaten by actress speaking theirown vs other language

The omnivore’s dilemma: culture

(from Sherman and Hash 2001)

Summary

The human diet

I humans depend more on meat and extracted foods than otherprimates

I human diet is more nutrient-dense

I human foods are hard to acquire (brain evolution?)

I cooking is universal, increases available nutrients

I humans are evolving adaptations to cultural dietary changes

The omnivore’s dilemma: how to choose safe, nutritiousfoods?

I taste preferences in newborns

I neophobia (especially high among toddlers)

I babies prefer what mother ate (learning in utero)

I children prefer what familiar people eat

I cultural traits can be fitness-enhancing (spices)

Summary

The human diet

I humans depend more on meat and extracted foods than otherprimates

I human diet is more nutrient-dense

I human foods are hard to acquire (brain evolution?)

I cooking is universal, increases available nutrients

I humans are evolving adaptations to cultural dietary changes

The omnivore’s dilemma: how to choose safe, nutritiousfoods?

I taste preferences in newborns

I neophobia (especially high among toddlers)

I babies prefer what mother ate (learning in utero)

I children prefer what familiar people eat

I cultural traits can be fitness-enhancing (spices)