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Plant and Animal Domestication

Plant and Animal Domestication. Jared Diamond, Guns, Germs, and Steel. 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

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Plant and Animal Domestication

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  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 • Seed Dispersal by Animals • 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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