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 – In rich environments, hunter-gatherers may have permanent settlements (Pacific Northwest) – May practice some agriculture along with hunting and gathering (Apaches) 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?) 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 The Fertile Crescent 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 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 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 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 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) 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 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 Plant Domestication • Single Mutation – Chance of getting multiple favorable mutations very slim • Self-Pollinated or Asexual Reproduction – Pollination from elsewhere would negate mutation 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 Fertile Crescent Founder Crops • • • • • • • • Emmer Wheat Einkorn Wheat Barley Lentil Pea Chickpea Bitter Vetch Flax North American Crops • • • • • • • Gourds Sunflower Sumpweed (seed crop) Goosefoot (leaf crop) Corn (from Mexico) Beans (from Mexico) Squash (from Mexico) Agriculture and Civilization Why the Link? • Need for organization, surveying, recordkeeping • Surpluses allow development of specialist classes • Protection? – Grain stores susceptible to raiding 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 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. 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) Suitable for Domestication • Docile (or selectable for docility) • Non-territorial • Dominance Heirarchy (Humans co-opt leadership role) • Uninhibited Breeding • Rapid Growth a plus 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 Self-Domestication Humans create an environment • Free of Predators • Abundant food • Salt 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 The Big Five • • • • • • Sheep Goat Cattle, Oxen Pig (Actually an Omnivore) Horse All are Eurasian 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) Why Eurasia? 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? 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 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 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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