Dissemination of Crops: Main Pathways

© Paul Gepts 2010

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PLB 143: Readings - Lecture 11

  • Required:
  • Additional readings:
    • Harlan, J.R. 1992. Chapters 8-11. pp. 159-236
    • Zohary D, Hopf M. 1988. Domestication of plants in the Old World. Clarendon, Oxford, U. K.
    • Purseglove, J.W. 1976. The origins and migrations of crops in Tropical Africa. In: Harlan (ed). Origins of African Plant Domestication. pp. 291-309.
    • Purseglove, J.W. 1968. Tropical Crops. Dicotyledons 1. pp. 9-17.
    • Smith BD. 1997. The initial domestication of Cucurbita pepo in the Americas 10,000 years ago. Science 276: 932-934
    • http://en.wikipedia.org/wiki/Malaria
    • http://www.cdc.gov/malaria/
    • Tishkoff SA, Varkonyi R, Cahinhinan N, Abbes S, Argyropoulos G, Destro-Bisol G, Drousiotou A, Dangerfield B, Lefranc G, Loiselet J, Piro A, Stoneking M, Tagarelli A, Tagarelli G, Touma EH, Williams SM, Clark AG (2001) Haplotype diversity and linkage disequilibrium at human G6PD: Recent origin of alleles that confer malarial resistance. Science 293:455-462.
    • Piperno DR, Dillehay TD (2008) Starch grains on human teeth reveal early broad crop diet in northern Peru. Proc Nat Acad Sci USA 105:19622-19627.
    • Fuller DQ (2007) Contrasting patterns in crop domestication and domestication rates: recent archaeobotanical insights from the Old World. Ann Bot 100:903-924.
    • Gray RD, Drummond AJ, Greenhill SJ (2009) Language phylogenies reveal expansion pulses and pauses in Pacific settlement. Science 323:479-483.
    • Piperno DR, Ranere AJ, Holst I, Iriarte J, Dickau R (2009) Starch grain and phytolith evidence for early ninth millennium B.P. maize from the Central Balsas River Valley, Mexico. Proc Nat Acad Sci USA 106:5019-5024.
    • Ranere AJ, Piperno DR, Holst I, Dickau R, Iriarte J (2009) The cultural and chronological context of early Holocene maize and squash domestication in the Central Balsas River Valley, Mexico. Proc Nat Acad Sci USA 106:5014-5018.
  • Presentation slides

The origin and spread of cultivated plants

  • Centers of origin and diversity
    • Near East
    • Africa
    • Far East: China and Southeast Asia
    • Americas
  • Main pathways of dispersal: Evidence
    • Archaeological
    • Botanical

Temporal sequence in crop domestication

(Hancock 1992)

  • From 10,000 to 9,000 BP on:
    • Cereal grains
    • Major legumes and root crops
    • Vegetables
    • Oil, fiber, fruit crops
  • From 2,000 BP on:
    • Forrage crops
    • Drug sources
  • Last 200 years:
    • rubber
    • sugar beet
    • blueberries, macadamia nuts

An example of complementarity in domestication: Cereals and Legumes

(According to Zohary 1993)

  • Cereals: Principal crops of most civilisations
    • Nutritive values is high
    • Long seed storage
    • Kernels rich in starch, sometimes protein
    • Higher yields than legumes
    • Need adequate soil fertility and nitrogen
  • Legumes: Companion crops to cereals
    • High protein content
    • Nitrogen fixers
    • Lower yields
    • Presence of some toxic compounds

The spread of crops in the Old World

The Near East or S.W. Asia

  • Area including: Israel, Jordan, Syria, Iraq, Iran and southern Turkey
  • General characteristics as center of origin of agriculture: 
    • Presence of wild relatives 
    • First definite signs of plant cultivation in the Old World
      • Tell-Aswad : Southwestern Syria, 7800 BC
    • Neolithic farming villages in the Near East date from 10th millenia BC
    • Food production based on a small number (8-9) of grain plants: FOUNDER CROPS
    • Simultaneous cultivation of plants and domestication of animals
      • sheep and goats followed by cattle and pigs.

  • The Near East "crop assemblage": 
    • Archaeological sites: e.g., Tell Abu-Hureyra (9100-8250 BC)
      • Epipaleolithic to Neolithic
      • Most numerous plant remains come from three cereals
        • Emmer wheat: Triticum turgidum
        • Einkorn wheat: T. monococcum
        • Barley: Hordeum vulgare
      • Emmer wheat and barley are the most common crops
      • Several grain legumes are also present:
        • Lentil: Lens sp.
        • Pea: Pisum sp.
        • Vetch: Vicia sp.
        • Chickpea: Cicer sp.
      • Wild forms of rye (Secale sp.) and oats (Avena sp.)
      • Flax, a fiber crop, is the last other component of the Near East "crop assemblage"
    • Mating systems:
      • All Neolithic "founder crops" are predominantly self-pollinated

  • The Near East crop assemblage

  • Diagnostic morphological traits:
    • Emmer and Durum wheats
      • Wild vs. cultivated wheats: non-brittle ears and broad kernels
      • Cultivated wheats: Hulled vs. free-threshing
        • Emmer: Hulled, more primitive grains surrounded by tough glumes and paleas, need pounding to free grains 
        • Durum: Free-threshing: more advanced, naked grains, thinner glumes don't invest grains 
      • Barley
        • Two-rowed vs. six-rowed barley: wild or primitive domestication vs. cultivated
      • Legumes: Lack traits by which initial stages of domestication can be recognized
        • Wild vs. domesticated: seed size and seed coat
  • Adaptation relevant to dispersal
    • Einkorn wheat:
      • Low yields, survive on poor soils, prefers cool climates, fed to animals.
      • Cultivation discontinued in the 1950s
    • Emmer wheat:
      • Wheat of the Mediterranean basin: mild winters and warm dry summers.
      • Food and brewing quality.
      • Area of adaptation more restricted than the wild einkorn.
      • Principal crop from 7500 to 6000 BC prevailing quantitatively over einkorn and barley.
    • Barley:
      • Considered inferior staple.
      • Withstands poorer soils, drier conditions and some salinity.
      • Replaces wheat in saline areas.
      • Mesopotamia 4th millenium BC
  • Glumes and paleas

Some related sites of interest

  • The spread of Near East crops
    • Main pathways of dispersal: Dispersal of crops into Europe is the best documented, evidence from Central Asia and Indian subcontinent is more fragmentary. Very scarce evidence from Africa.

      • Westward to Europe:
Direction Approx. date
Aegean region (Cyprus, Greece)
c. 6000 BC
einkorn, emmer,
Balkans (Yugoslavia, Bulgaria)
c. 5000 BC
einkorn, emmer, barley rare
Danubian region (Bandkeramik culture)
c. 4500 BC
einkorn, emmer, barley rare
Mediterranean basin
4800-4500 BC
emmer, barley, einkorn scarce

      • Southward to Africa (5,000-4,500 BC)
        • Nile Valley: emmer, barley , no einkorn found
        • Highlands of Ethiopia: emmer
      • Eastward to India, China (2,500-1,500 BC)
        • Harappa civilization: no einkorn, but emmer
      • Northeastward to former USSR, Transcaucasus (5,000 BC)
        • Djeitun: einkorn, emmer, barley
      • Legumes followed the same pathways but remains are less abundant
    • The second wave of crops: Horticultural crops: Horticulture spread from the Near East to the Mediterranean basin and SW Asia, soon after established. Difficult to distinguish wild from cultivated; Archaeological remains are rare, except in Egypt.
      • Fruit trees:
        • 3,500 BC:
          • Olive
          • Grape vine
          • Fig
          • Date palm
        • 1,000 BC:
          • Apple, pear
          • Plum, cherry
      • Vegetables:
        • 3,000-2,000 BC:
          • Garlic
          • Onion
          • Leek
          • Lettuce

Indigenous African agriculture

  • Contrast between amount of evidence for human presence and plant domestication Two differentiated areas delimited by the Sahara desert
    1. North of the Sahara and Egypt: Agriculture belonging to the Mediterranean World
    2. Sub-saharan Africa: Not explored until the 15th century
  • Archaeological sites: Merimde and Fayum (4000 BC) in the Nile Valley
    1. Typical Near East crop assemblage
      1. Cool-season crops
      2. Adapted to periodical Nile floods?
  • Archaeological sites: Nabta Playa (6000 BC), settlement, domestication? (from Wendorf et al. 1992 )
    1. Indigenous African crops:
      1. Sorghum and millets ( Panicum, Digitaria, Brachiaria, Setaria)
      2. Legumes
      3. Cruciferae

  • African biomes

  • Suggested dispersal of sorghum

  • African crops lack cohesion, many have very limited distributions and characterize specific biomes
    • Basic savanna type agriculture: "The savanna complex": drought tolerant crops
      1. Sorghum: Domestication resulted in specific races for different climatic conditions 
      2. Pearl millet: Pennisetum glaucum
      3. African rice: Oryza glaberrima
      4. Yams: Dioscorea sp.
      5. Bambara groundnut
  • Forest savanna
      1. Guinea millet: Brachiaria deflexa
      2. Cowpea: Vigna unguiculata
      3. Oil palm
  • True forest: Robusta coffee: Coffea canephora cv. Robusta

Two major areas of domestication suggested: Ethiopia and West Africa


The spread of crops out of and into Africa

  1. Major pathways out of Africa
    1. Southwards along each either side of the rift to South Africa (1000 BC)
      1. Sorghum: from Sudan, Ethiopia into East Africa and South (Bantu)
      2. Millet: from West Africa to Sudan and later to East and Central Africa
    2. Eastwards to India: From Ethiopia north to the Red Sea and along the Sabaean lane (Yemen)
      1. Sorghum, finger millet and bulrush millet (Pennisetum): 1000 BC
      2. Cowpeas, pigeon peas, sesame:100 BC
    3. Northwards to Arabia: Coffee with the Ethiopian conquest: 400-600 AD
    4. No dispersal of certain Ethiopian crops:
      1. Ensete
      2. Noog
  2. The spread of crops into Africa
    1. From the Far East: (through Persia)
      1. sugarcane, citrus, mango and pomegranate: AD 700
      2. bananas (Musa), asian rice and greater yam: AD 700-1000
    2. From the New World: With the Portuguese explorers
      1. Cassava, maize, common bean, peanut, sweet potato, chilies, cocoa, sisal, New World cottons, tobacco: AD 1500

Most of the New World crops became widespread and food staples having a profound effect in African agriculture.

The Far East


Mosaic of Neolithic cultures evolved in China between 6500-5000 BC

  • Northern China: P'ei-li-kang culture 6500 BC
    • Semiari
    • Based on millets (proso and foxtail millets
    • Favored by the existence of deep, fertile loess soil
    • Cultivation of Brassica
  • China

  • Southern China: Several ceramic cultures.
    • Plant cultivation along the Yangzte delta 5000 BC
    • Based on rice (Oryza sativa)
    • Cultivation of wetland roots and vegetable
      • Lotus( Nelum)
      • Arrowroot (Maranta arundinacea)
      • Water chestnut (Eleocharis dulcis)

The Book of Odes (1000 to 550 BC) describes 150 plants among them the most frequently cited Panicum millets. Soybean first cited c. 664 BC

The second wave of crops: later domesticates

  • Northern China
    • Mulberries as silkworm fodder
    • Hemp: Cannabis for fiber, food and oil
    • Soybean
    • Peach, apricot, persimmon
  • Southern China
    • Sour and sweet orange
    • Mandarin
    • Kumquat
    • Litchi
    • Tea

Southeast Asia

Sparse evidence for early domestication of crops

Southeast Asia archaeological sites
Archaeological sites: Spirit Cave, Thailand. (9200 BP)
  • No real evidence for early agriculture, no root crops, gathering of rice
    • Piper
    • Cucumis
    • Lagenaria
  • Agriculture started in coastal sites, low latitude forest regions, complement to fishing?
    Kuk, New Guinea: evidence for drainage or irrigation (7000 BC)
  • Crops include clonally propagated domesticates (1500 BC)
    • bananas (Musa)
    • taro
    • sago palm
    • sugar cane (Saccharum)
    • coconut

The spread of crops out of Asia

Far Eastern agriculture had very little dispersal until well into modern historic times

  • To Persia along the silk routes  (rice)
after 350 BC
  • To India  (peach)                                                           
AD 150
  • To Africa, Madagascar (banana)
AD 700-1000
  • To Southern Europe along Northern Africa with Islam (citrus)
7th century AD
Eastwards; cereal culture declined and rootcrops increased such as taro, breadfruit, sago, banana
  • To Philippines
3000 BC
  • To  Eastern Polynesia and  Hawaii 
AD 300
  • To New Zealand (Maori) 
AD 1050

The New World

A substantial fraction of the World's most important crop plants:( maize, potatoes, manioc, beans, peanuts, sunflower, tomato, upland cotton and tobacco) come from the Americas.

  • Two independent centers?
    • Mesoamerican: Seed crop agriculture
    • Andean: Tuber crop agriculture (vegetatively propagated crops)
      • absence of a grain crop
      • presence of non-food crops (fiber): upland cotton and gourds.
  • Several crops domesticated in both areas
    • Phaseolus, Amaranthus, Chenopodium, Cucurbita and Capsicum
  • Other crops restricted to only one area
    • Maize: Mexico
    • Potato: Peru

Later record for Homo presence compared to the Old World. Civilizations such as: Chavín, Aztec, Olmec, Maya, Inca

  • Archaeological sites 
    • Mesoamerica:
      • Tehuacán, Central Mexico (7000 BC)
        • Maize, peppers, cotton, bottle gourd
      • Guilá Naquitz, Oaxaca (8000-6000 BC)
        • Squash (see Smith 1997)
    • Highlands of Peru: Guitarrero Cave, Callejón de Huaylas (8500 BC)
      • 8500-5600 BC: peppers, lima and common beans, squash, oca, lucuma
      • 5600-500 BC: maize, oca
      • 500 BC- AD 500: peanut, oca

  • Archaeological sites

Dispersal of crops into the New World

  • Exchanges between the two American centers
    • Maize
      • North and Eastwards into North America by 6000 BC 
      • Southward to the Orinoco river and Brazil by 4500 BC
        • phytoliths , Panama by 5000 BC
        • chromosome studies, Brazil
    • Other crops:
      • Cacao, cassava, peppers, beans
  • Eastwards to Europe:
    • AD 1493, 2nd trip of Columbus: maize and sweet potatos to Spain
    • Portuguese routes (AD 1500-1665)
      • via Brazil to China and SE Asia (Macao, Formosa) and Japan
      • to Africa via the slave traffic between West Africa and Brazil
    • Spanish galleon line between Acapulco and Philippines (AD 1565-1815)

  • Introduction of maize in North America

Summary of the lecture

  • Crop dispersal is a lenghty process that begun several thousand years ago and still continues
  • The major event in the dispersal of crops is a relatively modern one. The discovery or conquest of the Americas in 1492 has had a major influence on the crop distribution of the Old World. This is the so-called "Columbian exchange".

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