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

Transcription

1 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 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? KratzerMD.com 1

2 Outline 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 The Paleo diet is now gaining mastodon like momentum. 2

3 Paleo Diet Paleolithic Diet Initially based on books by S. Boyd Eaton & Mel Konner and Loren Cordain The estimated diet that the Paleo movement is based on Started as diet became lifestyle, fitness regimen, and eventually the paleo craze diet Would have been diets not one (based on ecology and seasonal variation) Paleodiet.com Paleoemergencyfood.com 3

4 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 4

5 The Hadza of Tanzania Geography Demography Diet composition The Hadza: Last of the First Wycliffe Global Alliance 5

6 The Hadza Foragers Northern Tanzania ~ Lake Eyasi Approximately 1000 individuals (200 hunt and gather) Camp membership is fluid ~ 30 residents Camp size fluctuations correspond to seasonality 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 ~ kcal/100g Berries ~ kcal/100g Figs ~ 251 kcal/100g Legumes ~ 35 kcal/100g Tubers ~ 169 kcal/100g Undushabe berry (Cordia senensis) 6

7 The significance of seasonality Hadza Diet Compositio T raded Foods 13% 11% 13% 8% 14% 7% 9% Baobab Berries and Figs Birds, Small & Medium Game Large Game Honey T ubers 25% Nuts and Legumes 7

8 WET SEASON DIET Total Kilocalories 8% 2% 15% 7% Baobab Berries Maize Honey Fruits, Nuts, Legumes Birds Big Game Small+Medium Game Tubers 7% 43% 0% 14% 4% DRY SEASON DIET Total Kilocalories 8

9 Hadza Diet Total Kilocalories by Food Type P urc has ed Foods M eat H oney Fruit, N uts, L egumes T ubers Hadza diet composition can inform our understanding of the evolution of the human diet Significance of: * meat * honey & larvae * tubers 9

10 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 subtropical foraging population) 10

11 Hadza Honey Hunting Honey & 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 11

12 Tubers are available year round and compose 13% of the overall diet The Hadza by James Woodburn (1966) 12

13 Summary of results 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 Photo: Matthew Oldfield 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 Potential Limitations Metabolism, 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 13

14 TIM 1 In-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? 14

15 Photo: S. Schnorr Photo: S. Schnorr 6/1/2015 How do we measure bioaccesibility the fraction of nutrition reaching circulation? Go from the field.. to the laboratory 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 15

16 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? 16

17 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 17

18 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 18

19 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 19

20 Meat in human evolution? Butchery patterns Stable isotope analysis Microwear analysis Bradshawfoundation.com Honey in human evolution? The brain is an obligate glucose consumer and honey might have fueled the neurological expansion of early Homo Mesolithic rock painting from La Valencia, Spain 20

21 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 21

22 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 The Hadza: Last of the First Plant foods make up large portions of HG diets (including starchy tubers) You are what your gut bacteria eat! 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 22