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Plant and Animal Domestication

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Presentation on theme: "Plant and Animal Domestication"— Presentation transcript:

1 Plant and Animal Domestication

2 Jared Diamond, Guns, Germs, and Steel

3 Why Farm? Hunting and gathering can supply a day’s calories with a couple of hours’ work Many early farmers less well off than hunter-gatherers Line between hunter-gatherers and farmers is fuzzy In rich environments, hunter-gatherers may have permanent settlements (Pacific Northwest) May practice some agriculture along with hunting and gathering (Apaches)

4 The Ice Age and Agriculture
Sea level rise stops about 7000 years ago Agriculture spreads widely roughly same time Stable coastal plain and river valley environments Warm, dry climate favors spread of wild grains Extinction of megafauna (and domestication candidates?)

5 Mediterranean Climate
Dry Summer, Rainy Winter Favors plants with seeds that can survive long dry periods These seeds can be stored for extended periods Will not spoil or germinate while dry Eurasian Mediterranean is world’s largest zone, greatest ecological diversity in small areas

6 The Fertile Crescent

7 Large Seed Grasses 56 species, <1% of total grass species
Eurasian Mediterranean 32 species Rest of Eurasia 7 species Sub-Saharan Africa 4 species North America 4 species Mesoamerica 5 species South America 2 species Australia 2 species

8 Human Plant Environments
Select desirable plants in wild Some seeds, fruits scattered at habitation site Other seeds deposited in wastes Eventually have desirable plants growing close-by Protection from foragers Seed collection

9 Plant Domestication More than just planting seeds or transplanting
Most plants inedible or otherwise unusable Most plants unsuited for primitive domestication Not every locality has abundant plants suitable for human use Need nutritional balance Requires changes in plant characteristics

10 Highland New Guinea Simple agriculture for thousands of years
Active experimentation and inquiry Chronic protein deficiency Introduction of sweet potato (South America via Philippines) caused population boom These people knew their environment as well as any people on earth If any local plants could have been successfully domesticated, they would have found them

11 Five Levels of Domestication
Unconscious selection of plants for desirable traits (9000 BC) Conscious cultivation of plants with desired traits (BC) Deliberate breeding to improve traits (1700) Scientific breeding: genetic mechanism known and exploited (1900) Direct genetic manipulation (2000)

12 Reversing Natural Selection
Seed Scattering Non-bursting pods (peas) Non-shattering heads (grains) Fruits without seeds Germination Inhibition Nature: favors seeds that germinate slowly and over time Agriculture: favors seeds that germinate quickly all at once

13 Reversing Natural Selection
Deterrents Loss of Toxicity (Almonds) Changes in Reproduction Asexual Reproduction Self-Fertilization (Hermaphrodites) Annuals favored: would evolve more quickly under artificial selection

14 Plant Domestication Single Mutation
Chance of getting multiple favorable mutations very slim Self-Pollinated or Asexual Reproduction Pollination from elsewhere would negate mutation

15 Some Non-Domesticates
Oaks Food Source in Many Places Grow Slowly Bitterness Controlled By Many Genes Seed Dispersal by Animals Berries Domesticated only after greenhouses invented

16 Fertile Crescent Founder Crops
Emmer Wheat Einkorn Wheat Barley Lentil Pea Chickpea Bitter Vetch Flax

17 North American Crops Gourds Sunflower Sumpweed (seed crop)
Goosefoot (leaf crop) Corn (from Mexico) Beans (from Mexico) Squash (from Mexico)

18 Agriculture and Civilization
Why the Link? Need for organization, surveying, record-keeping Surpluses allow development of specialist classes Protection? Grain stores susceptible to raiding

19 Animal Domestication Genetic change that makes animal more amenable to human control Not the same as: Taming Training Captive Breeding A lot more complicated than just capturing and taming animals

20 Animal Domestication Happy families are all alike. Every unhappy family is unhappy in its own way. --Tolstoy, Anna Karenina Lots of things have to work for success. Failure in any one means failure of it all.

21 Unsuitable for Domestication
Ferocity (Zebras, Rhinos, Hippos) High Trophic Level (Carnivores) Picky Diet (Pandas, Koalas) Slow Growth (Elephants) Territoriality (Deer, Antelope) Large Range Solitary Habits Reclusive Breeding or Elaborate Courtship (Cheetahs) Tendency to Panic (Gazelles)

22 Suitable for Domestication
Docile (or selectable for docility) Non-territorial Dominance Heirarchy (Humans co-opt leadership role) Uninhibited Breeding Rapid Growth a plus

23 Thyroxine Governs many growth and maturation characteristics
Governs adrenaline (fear response) Low thyroxine traits: Reduced snout (pedomorphism) Solid or patchy colors More frequent reproduction Larger litters

24 Self-Domestication Humans create an environment Free of Predators
Abundant food Salt

25 Animal Domestication 148 Species of Large Herbivores (>50 kg)
Eurasia 13/72 (18%) Domesticated Sub-Saharan Africa 0/51 Domesticated Americas 1/24 (4%) Domesticated Australia 0/1 Domesticated

26 The Big Five Sheep Goat Cattle, Oxen Pig (Actually an Omnivore) Horse
All are Eurasian

27 The Lesser Nine Arabian and Bactrian Camels (Eurasia) Donkey (Eurasia)
Water Buffalo (Eurasia) Yak (Eurasia) Bali Cattle, Mithan (Eurasia) Reindeer (Eurasia) Llama (including Alpaca) (South America)

28 Why Eurasia?

29 Why Eurasia? Only Land Mass with east-west axis Other barriers
Panama and Caribbean Rain Forest (Africa) Trypanosome Belt (Africa) Extinction of Megafaunas Not adapted to humans and vice versa Possible candidates for domestication wiped out?

30 Why Not Domestication? Buffalo (bison) and elk successfully farmed in modern times Have attributes that seem promising for domestication Wild grapes in America not cultivated If advantages marginal, domestication may not happen even if possible Indians adapted to Horses Very Quickly

31 Domesticated Carnivores
Dogs Have dominance hierarchy that humans can co-opt Cats Probably attracted to prey around grain stores At best partially domesticated Ferrets Recently popular as pets but long used for pest control Probably many of same factors as cats

32 Small Animal Domestication
Thousands of Candidates Distinction between Domestication and Captive Rearing fuzzier Do We Really Care if a Rabbit is Captive or Domesticated? Very Rapid Breeding Cycle

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