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

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Meagan Walker
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1 Problems of survival (3): Diet and the omnivore s dilemma The human diet forager vs. chimp diet cooking recent evolutionary changes Solving the omnivore s dilemma sweet and bitter tastes learning biases: neophobia taste-aversion learning social learning culture (spices and cuisine)

2 Man the hunter?

3 Human forager vs. chimp diets vert. nuts/ other meat roots seeds fruits plant insects Onge Anbarra Arnhem Ache Nukak Hiwi Gwi Hadza CHIMP Dietary percentage of foraged foods, from Kaplan et al. 2000

5 Human forager vs. chimp diets (from Kaplan et al. 2000)

6 The advantages of cooking Change in digestibility from cooking: Starch source Raw Cooked % increase Wheat % Oats % Barley % Green banana % Plantain % Potato % Pea % (from Carmody and Wrangham 2009)

7 Recent changes: Lactase persistence evolved in dairy farming communities in central Europe first evolved about 7500 years ago evolved independently in Africa and Middle East

8 Recent changes: Amylase copy number amylase digests starch in saliva, varies by copy number more copies means more amylase

9 The Omnivore s Dilemma The human diet forager vs. chimp diet cooking recent evolutionary changes The omnivore s dilemma: which foods are toxic? which foods are most nutritious? how can we know?

10 Solving the omnivore s dilemma: sweet and bitter tastes newborns react more positively to sugar solutions than water most infants dislike bitter and sour tastes around 4 months, infants develop liking for salty tastes reaction of a two-week old baby to taste of sugar and lemon juice

11 Solving the omnivore s dilemma: Neophobia rats are also food neophobic; eat a small amount at first willingness to try new foods is greatest during the first two years

12 The omnivore s dilemma: Social learning young rats prefer foods mothers ate when pregnant and nursing

13 The omnivore s dilemma: Social learning young rats prefer foods mothers ate when pregnant and nursing young rats forage where adults are foraging

14 The omnivore s dilemma: Social learning young rats prefer foods mothers ate when pregnant and nursing young rats forage where adults are foraging adult rats prefer food if have smelled on breath and body of other rats

15 The omnivore s dilemma: Social learning young rats prefer foods mothers ate when pregnant and nursing young rats forage where adults are foraging adult rats prefer food if have smelled on breath and body of other rats howler monkey infants: copy mom when eating leaves, not fruits

16 The omnivore s dilemma: Learning in utero Babies intake of carrot-flavored cereal compared to plain cereal (from Mennella et al. 2001)

17 The omnivore s dilemma: Social learning human babies more likely to take novel food from mom than stranger

18 The omnivore s dilemma: Social learning human babies more likely to take novel food from mom than stranger human babies more likely to take novel food from stranger if stranger eats first

19 The omnivore s dilemma: Social learning human babies more likely to take novel food from mom than stranger human babies more likely to take novel food from stranger if stranger eats first human babies choose food eaten by actress speaking their own vs other language

20 The omnivore s dilemma: culture (from Sherman and Hash 2001)

21 Summary The human diet humans depend more on meat and extracted foods than other primates human diet is more nutrient-dense human foods are hard to acquire (brain evolution?) cooking is universal, increases available nutrients humans are evolving adaptations to cultural dietary changes

22 Summary The human diet humans depend more on meat and extracted foods than other primates human diet is more nutrient-dense human foods are hard to acquire (brain evolution?) cooking is universal, increases available nutrients humans are evolving adaptations to cultural dietary changes The omnivore s dilemma: how to choose safe, nutritious foods? taste preferences in newborns neophobia (especially high among toddlers) babies prefer what mother ate (learning in utero) children prefer what familiar people eat cultural traits can be fitness-enhancing (spices)

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