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
Onge
Anbarra
Arnhem
Ache
Nukak
Hiwi
Gwi
Hadza
CHIMP
vert.
meat
79
75
77
78
41
75
26
48
2
roots
19
8
19
0
0
15
37
30
0
nuts/
seeds
0
0
0
0
0
0
0
0
5
fruits
0
4
0
1
40
5
37
15
60
other
plant
0
0
0
9
0
2
0
0
29
insects
2
12
3
11
20
3
0
0
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
Wheat
Oats
Barley
Green banana
Plantain
Potato
Pea
Raw
71
75
93
49
54
97
80
(from Carmody and Wrangham 2009)
Cooked
96
96
99
97
100
51
91
% increase
34%
28%
6%
96%
87%
91%
14%
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
I
amylase digests starch in saliva, varies by copy number
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
neophobic children more averse to vegetables
I
in humans, neophobia peaks among toddlers
The omnivore’s dilemma: Social learning
I
young rats prefer foods mothers ate when pregnant and
nursing
The omnivore’s dilemma: Social learning
I
young rats prefer foods mothers ate when pregnant and
nursing
I
young rats forage where adults are foraging
The omnivore’s dilemma: Social learning
I
young rats prefer foods mothers ate when pregnant and
nursing
I
young rats forage where adults are foraging
I
adult rats prefer food if have smelled on breath and body of
other rats
The omnivore’s dilemma: Social learning
I
young rats prefer foods mothers ate when pregnant and
nursing
I
young rats forage where adults are foraging
I
adult rats prefer food if have smelled on breath and body of
other rats
I
howler monkey infants: copy mom when eating leaves, not
fruits
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 than
stranger
The omnivore’s dilemma: Social learning
I
human babies more likely to take novel food from mom than
stranger
I
human babies more likely to take novel food from stranger if
stranger eats first
The omnivore’s dilemma: Social learning
I
human babies more likely to take novel food from mom than
stranger
I
human babies more likely to take novel food from stranger if
stranger eats first
I
human babies choose food eaten by actress speaking their
own 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 other
primates
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
Summary
The human diet
I
humans depend more on meat and extracted foods than other
primates
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, nutritious
foods?
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)