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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 SelectionSeed Scattering• Non-bursting pods (peas)• Non-shattering heads (grains)• Fruits without seedsGermination 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-DomesticatesOaks• Food Source in Many Places• Grow Slowly• Bitterness Controlled By Many Genes• Seed Dispersal by AnimalsBerries• 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, record-
keeping• 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