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What Hunter-Gatherers Can Tell Us About the History of the Human Diet

Alyssa N. Crittenden

Lincy Assistant Professor

Department of Anthropology

University of Nevada, Las Vegas

KratzerMD.com

Evolution of Human Nutrition

• What is our body adapted to eat?

• What is our ancestral diet?

• Based on climate changes in the Pliocene

• Key anatomical changes in brain size, dentition, gut morphology

• What can hunter-gatherers tell us about the history of the human diet?

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• “Paleo” diet vs. Paleolithic diet

• Evolution of human diet

• Why Hunter Gatherer populations are important

• The Hadza of Tanzania

• Diet composition

• Meat, honey, and tubers

• In-vitro digestion

• Glucose absorption

• Gut microbiome

• Taxonomy and metabolic activity

• Other lines of evidence

• Putting it all together“Primal Living in the Modern World”

Outline

The Paleo diet is now gaining “mastodon like momentum” ….

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Paleo Diet

Initially based on books by S. Boyd Eaton & Mel Konner and Loren Cordain

Started as diet – became lifestyle, fitness regimen, and eventually the paleo craze

Paleolithic Diet

The estimated diet that the Paleo movement is based on

Would have been diets – not one diet (based on ecology and seasonal

variation)

Paleodiet.com Paleoemergencyfood.com

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Paleolithic Diet(s)

Paleolithic foods would have likely included:

• plant products

• meat (including insects)

• nuts

• fiber

• carbohydrates (including honey)

Paleolithic foods would NOT have included:

• whole grains

• dairy products

• alcohol

Hunter gatherers as a model of Paleolithic nutrition

• No universal HG diet exists (or existed)

• Wide variation based on ecology, climate, and food availability

• Reliance on plant foods ranges from 6-15% in tundra and 35-60% in grasslands

Navin Ramankutty

Ohio State University

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The Hadza of Tanzania

• Geography

• Demography

• Diet composition

The Hadza: Last of the First

Wycliffe Global Alliance

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• Northern Tanzania ~ Lake Eyasi

• Approximately 1000 individuals (200 hunt and gather)

• Camp membership is fluid ~ 30 residents

• Camp size fluctuations correspond to seasonality

The Hadza Foragers

Nutritional Composition of Hadza Foods• Honey - low in protein and fat (did not include larvae) and high mono and disaccharides

• Baobab - high in protein (flour), fat (seeds), and fiber; low mono and disaccharides

• Berries - low in fat, relatively low in protein, high in mono and disaccharides

• Legumes - high in protein, fiber, low in fat and mono and disaccharides

• Figs - high in fat, fiber, and mono and disaccharides; low in protein

• Drupes – low in fat and protein; high in fiber and mono and disaccharides

• Honey ~ 400 kcal/100g

• Baobab seed ~ 400 kcal/100g

• Baobab pulp ~ 200-250 kcal/100g

• Berries ~ 100 - 200 kcal/100g

• Figs ~ 251 kcal/100g

• Legumes ~ 35 kcal/100g

• Tubers ~ 169 kcal/100g

Undushabe berry (Cordia senensis)

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The significance of seasonality…

Hadza Diet Composition

8%

14%

9%

7%

25%

11%

13%

13%

Traded Foods

Baobab

Berries and Figs

Birds , Small &Medium Game

Large Game

Honey

Tubers

Nuts and Legumes

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7%

43%

4%

14%

0%

7%

8%

2%

15%

Baobab

Berries

Maize

Honey

Fruits, Nuts, Legumes

Birds

Big Game

Small+Medium Game

Tubers

WET SEASON DIET – Total Kilocalories

DRY SEASON DIET – Total Kilocalories

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0

1000 000

2000 000

3000 000

4000 000

5000 000

6000 000

7000 000

8000 000

P urchas ed

Foods

M eat Honey Fruit, Nuts ,

Legumes

T ubers

Hadza Diet

Total Kilocalories by Food Type

Hadza diet composition can inform

our understanding of the evolution of

the human diet

Significance of:

* meat

* honey & larvae

* tubers

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Meat composes bulk of dry season diet and only 32% of overall diet

Role of meat in hunter-gatherer diet?

• Wild game meat is:

• lower in saturated fat

• provides moderate to high protein

and fat

• higher in mono- and polyunsaturated

fatty acids

• While meat is important, particularly

seasonally, it is NOT the main component

of Hadza diet (or of any other sub-

tropical foraging population)

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Hadza Honey HuntingHoney & larvae compose

15% of wet season diet and

11% of overall diet

• Honey is the most highly ranked Hadza food

• Consumed by every sub-tropical foraging

population for which we have data

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Tubers are available year round and

compose 13% of the overall diet

The Hadza by James Woodburn (1966)

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• Wide inter and intra-species variation

• Seasonal variation linked to % moisture content

• Energy values can differ depending on how:

• fiber is analyzed

• unabsorbed calories pass through digestive system

• energy to host vs. energy to gut microbiota is

estimated

Summary of results

Although we now have reliable standards for dry matter estimates, we do

not know the amount of bioavailable energy – more detailed digestion

analysis is needed to determine energy contributions

Photo: Matthew Oldfield

Potential LimitationsMetabolism, Anthropometry, and Nutrition Lab at UNLV and the Plant Foods in

Hominin Evolution Lab at Max Planck Institute of Evolutionary Anthropology are:

(1) Measuring glucose absorption by in-vitro digestion

(2) Analyzing gut microbiota

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TIM 1In-vitro Digestion

TNO in-vitro model of the stomach and small intestine

• Humans have an unspecialized digestive system

• a reduction in the size of the colon and the overall size of the gut and an enlargement of the small intestine

• Gut morphology for high quality foods (i.e. relatively easy to digest)

• How much of the tuber is actually “digestible”?

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How do we measure bioaccesibility – the fraction of nutrition reaching circulation?

Go from the field….. to the laboratory

Pho

to: S. Sch

norr

Pho

to: S. Sch

norr

• For Hadza tubers, much of plant

defense is physical – plants are

covered in fibrous inedible bark

• Important for nutritional

anthropologists to understand how

inedible constituents become

available through digestion

Photo: S. Schnorr

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Analysis of tubers

• High variation in digestibility

• Roasting is likely not impacting digestibility

• Roasting helps peeling and softens tubers for mastication

• How do the Hadza digest such fibrous plant foods?

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Gut microbiota composition and activity

• We compared Hadza gut microbiota with that of urban Italians

• Hadza have an entirely unique configuration of gut bacteria

• more diverse bacteria

• low levels of Bifidobacterium (“good”)

• high levels of Treponema (“bad”)

• Increased Treponema among women and juvenile girls

• may be linked to higher amount of fiber in their diet

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• Conducted the first metagenomic analysis of

HG gut microbiota (GM)

• Hadza have a unique enrichment in metabolic

pathways that aligns with diet and ecology of

foraging lifestyle

• GM is adapted for broad-spectrum

carbohydrate metabolism, reflecting the

complex polysaccharides in their diet

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• The Hadza gut metagenome structure highlights the co-adaptive functional role of the GM in complementing human physiology throughout our evolution

• This indicates a flexible functional structure capable of efficient energy capture from wild and seasonal foods

Other lines of evidence

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• Meat in human evolution?

• Butchery patterns

• Stable isotope analysis

• Microwear analysis

Bradshawfoundation.com

Mesolithic rock painting from La Valencia, Spain

• Honey in human evolution?

• The brain is an obligate glucose consumer

and honey might have fueled the

neurological expansion of early Homo

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• Tubers in human evolution?

• Replicas of 2mya Oldowan stone tools were used by Hadza women to process wild tubers

• Tuber processing use-wear reflects abrasion of artifact edges by grit on tubers

• Micro-traces from Oldowan tools show the same striation patches as Hadza tools

• These data extend archaeological evidence of tuber consumption by human ancestors

Photo: Tom Plummer

Putting it all together

Eatdrinkpaleo.com

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• There is no single Paleo diet – varied diet is

what likely characterized the Paleolithic

• Energy is a meaningful unit in dietary

reconstructions and must be considered

carefully

• Meat is important – but varies by season,

region, and climate

• Honey was likely a critical component of the

early human diet

• Plant foods make up large portions of HG

diets (including starchy tubers)

• You are what your gut bacteria eat!

The Hadza: Last of the First

Acknowledgements

Funding:

National Science Foundation

National Institutes of Health

University of California, San Diego

Harvard University

University of Nevada, Las Vegas

Lincy Foundation - UNLV

Collaborators:

Colette Berbesque

Laura Bishop

David Braun

Nancy Conklin-Brittain

Peter Ditchfield

Amanda Henry

Fritz Hertel

Christina Lemorini

Sarah Livengood

Frank Marlowe

James Oliver

Tom Plummer

Richard Potts

Stephanie Schnorr

Margaret Schoeninger

Peter Ungar

Brian Wood

Richard Wrangham

Tanzanian research support:

COSTECH and NIMR, Tanzania

Pastory Bushozy

Audax Mabulla

Happy Msofe

Ephraim Mutukwaya

Golden Ngumbuke

Student research support:

Jackie Benjamin

Divya Bhat

Kristen Herlosky

Kara Osborne

Kilian Wells

★ My continued gratitude to the Hadza, who

welcome me into their lives and make this type of

work so enjoyable