What did humans evolve to eat?
Human nutritional health in comparative perspective
WR Leonard
Department of Anthropology
Northwestern University
Financial Disclosures: WR Leonard, PhD
• I have nothing to disclose
The Rise of Evolutionary Medicine
Books
Journals
Scientific Organizations
Evolutionary Perspectives on
Human Nutrition
• Particular interest in the evolution of human
nutritional requirements
• Nutritional implications of changes in human
evolution
• Evolutionary perspective useful for
understanding today’s nutritional problems
What did Humans Evolve to eat?
• Is there a single “natural” human Paleodiet?
Diversity of Modern Human
Nutritional Strategies
Chuño (freeze-dried potato) production
in the Peruvian Altiplano
Siberian herder (Evenki)
preparing reindeer meat
Lowland Bolivian woman (Tsimane’)
pounding rice
Human Evolution:
A Nutritional Story
• Major Trends in:
– Eating/Foraging Patterns
– Diet Quality
– Energy Allocation & Energy Balance
• Increased efficiency of energy extraction
• Evolution of Dietary Diversity
Homo erectus:
The Emergence of Human Nutritional Ecology
• Increased brain size
and body size
• Changes in foraging
behavior & diet
•  profound influences
on human nutritional
needs
Table from: SC Antón et al. 2014. Science 345:1236828-9
Key features of Human nutritional
needs established in Homo erectus
• High quality Diet to support the high costs of
brain metabolism
• High Activity & Energy Demands.
Foraging regimes requiring large activity
budgets.
Overview
• Energetic & Dietary Correlates of Variation in
Body Size & Brain Size in living primates
• Diversity of Dietary & Activity Patterns in
Human Societies
– Subsistence vs. Industrialized populations
• Implications for understanding modern
nutritional problems
The “Expensive Brain”
Metabolic Rates of Selected Tissues
a) Mass specific
b) Total Energy Costs
Data from: MA Holliday. 1986. in: Human Growth, Vol. 2 (2nd Ed.), p 101.
Brain Weight vs. RMR:
Primates & Non-Primate Mammals
Percent (%) of Body’s Energy for the Brain
Mammals, Primates & Humans
from: WR Leonard & ML Robertson. 1994. AJHB 6:77
Percent of Metabolism
for the Brain During Growth
Birth = 53%
4 yr = 66%
Adult = 20%
Adapted from: CW Kuzawa et al. 2014. PNAS 111:13010.
Dietary & Energetic Correlates of Size
Pygmy Marmoset
Gorilla
(110 grams = 3.9 ounces)
(145 kg = 340 lbs )
Small Body
Small volume; high quality diet
Large Body
Large volume; low quality diet
Diet Quality vs. Body Weight
in Primates
r = -0.66
Adapted from: Leonard & Robertson (1994) AJHB 6:77.
Percent (%) of Dietary Energy from Fat,
Protein & CHO: Human & Apes
Species/Group
Fat
Protein
CHO
Humans (Homo sapiens):
United States (2006)
34
15
51
28-58
19-35
22-40
Chimpanzees (Pan troglodytes)
6
21
73
Gorilla (Gorilla gorilla)
3
24
73
Modern foragers
from: WR Leonard et al. 2010. In: JP Montmayeur & J le Coutre (eds)
Fat Detection, p 5.
Relative Brain Size vs. Diet Quality
r = 0.63
from: WR Leonard et al. 2007. Ann Rev Nutr 27:311.
Relative Proportions of Small and
Large Intestines in Humans & Apes
Data from: K Milton. 1987. in: Food and Evolution, p. 95.
Day Range Variation:
Humans & Other Primates
**
**P < 0.01
from: WR Leonard, ML Robertson. 1997. CA 38:304.
Energy Expenditure in Apes vs. Humans:
(Physical Activity Level = TEE/BMR )
**
Humans
PAL (TEE/BMR)
Apes
**
Apes vs. Humans:
**P < 0.01
Ape data from: H Pontzer et al. 2014. PNAS 111:1434.
Human data from: WR Leonard. 2012. Human Biol, p. 281.
H. erectus at 1.8 million year ago:
A Major Adaptive Shift
• Increase in both brain &
body size
• Human-like body
proportions
• Evidence for increased
hunting & meat eating
Early African
H. erectus
• Rapid expansion from
Africa
Initial Spread of Homo from Africa
~1.8 million years ago
from: SC Antón et al. 2014. Science 345:1236828-9
Strategies for Promoting Diet Quality
in More Recent Human Evolution
Evolution of tool
technologies
Cooking
Agriculture
Nutritional Adaptations in Recent Human Evolution
• Animal herding & Milk digestion
Europe: ~7,500 years ago
East Africa: ~7,000 years ago
Spread of Lactase Persistence in Europe
from: Y Ital et al. 2009. PloS Comp Biol 5(8): e1000491.
• Agriculture & Enhanced Starch
Digestion
< 10,000 years ago
Variation in Amylase Gene Copies
from: J Novembre et al. 2007. Nat Genet 10:1189.
• Arctic Expansion & Increased
Energy and Fat metabolism
< 20,000 years ago
Elevated Metabolic Rates in Siberians
from: WR Leonard et al. 2005. Ann Rev Anth 34:451.
Novel food processing techniques
in Modern Human Populations
• Alkali Processing of
Maize (Americas)
• Potato dehydration
techniques (Andes)
• Processing
(detoxifying) of bitter
Cassava/Manioc
Amazonia (Tsimane’):
17% Animal foods
Arctic
(Evenki):
40-50%
High Andes (Quechua)
Animal foods
10% Animal foods
BMI Variation
Subsistence & Industrial Populations
*
Healthy BMI = 18.5- 24.9
*P < 0.05, relative to each subsistence group
*
Healthy BMI = 18.5- 24.9
Prevalence of Obesity in US Adults:
1960 to 2014
Data from: CL Ogden et al. 2012. JAMA 307:491; CL Ogden et al. 2015. NCHS Data Brief no. 219.
Changes in Daily Energy Intake &
Body Weight in US Adults: 1971-2010
from: WR Leonard. 2014. Physiol & Behav 134:10.
Total Energy Intake vs. Basal Metabolic Rate:
Subsistence & Industrial Populations
a) TEI vs. BMR
b) Mean (+SE) TEI/BMR Ratios
TEI = 2.0xBMR
TEI = 1.5xBMR
TEI = BMR
Percent of Dietary Energy from Animal Foods:
Subsistence & Industrial Populations
Dietary Macronutrient Composition:
Subsistence & Industrial Populations
US Dietary Reference 2006
“Acceptable Ranges”:
Protein: 10-35%
Fat:
20-35%
CHO:
45-65%
Sugar consumption in the US
a) Energy (kcal/d) from added sugar in US adults;
2005-2010
b) Historic trends in US sugar consumption:
1822-2005
~19% of TEI
From: RB Ervin & CL Ogden (2013) NCHS Data Brief No. 122
From: SJ Guyenet & J Landon (2012) Whole Health Source.
Differences in Dietary Fats:
Subsistence & Industrial Populations
• Subsistence Populations:
– Wild/Free-ranging animals
– lower fat content
– higher levels of mono- and polyunsaturated fats
• Industrialized Populations:
– Feedlot animals
– higher fat content
– higher levels of saturated fats
Measuring Energy Expenditure & Work
Capacity among Subsistence-level populations
Physical Activity Levels (PAL)
in Subsistence & Industrialized Populations
**
Intense
*
Intense
Moderate
Moderate
Light
Light
*P < 0.05
**P < 0.01
n=
117
236
n = 142
257
Increased Energy Costs of Shifting from an
Industrial to Subsistence Society Activity Budget
+411 kcal/day
+210 kcal/day
Implications of adding 1 hour of Exercise
to the Industrialized Society Lifestyle
 Matches Energy Costs of Subsistence Lifestyle
a) Men
b) Women
2494
3204
3285
2234
2874
Industrial + exercise = +1 hour vigorous exercise
2444
Physical Activity in Subsistence Populations:
Sustained, modest increases in metabolism
Reduced Energy
& Activity for
Subsistence
Increased Food
Availability & Energy
Density of the Diet
-
+
INTAKE
EXPENDITURE
Modern Life: A “Shifting” Energy Balance
Implications for Understanding the
Obesity Problem
• Nutritional recommendations must give
greater attention to physical activity
• Debate over how much PA is necessary for a
healthy lifestyle
 Comparative, evolutionary approach relevant for
answering this question
Conclusions:
• Evolution: offers insights into:
– Origins of distinct nutritional needs
– Modern constraints
• Humans did not evolve to consume a single
“natural” Paleodiet
• Rather, we evolved diverse strategies for
meeting our distinctive needs:
– High quality diet
– Large activity budgets and Energy Expenditure
Acknowledgments
• Collaborators: M Robertson, JJ Snodgrass, MV
Sorensen, S Antón, CW Kuzawa, T Klimova, MH
Crawford, R. Godoy, TW McDade, V Reyes-Garcia
• Support from: US National Science Foundation, US
National Institutes of Health, National Science &
Engineering Council of Canada, National Geographic
Society, Northwestern University