Diffused centres of origin
- 1. Diffused centres of origin Presented By Divya S (2019608004) I Ph D Genetics and Plant Breeding
- 2. Introduction - Diffuse origins of crops • Harlan first used the term diffuse origins in 1956 in a genetic and diffusionist sense • Our sophisticated high-yielding varieties of bread wheat are very different from the first primitive bread wheats that probably originated as spelts somewhere near the southern Caspian • The Borlaug wheats that have been so influential on the world scene originated in Mexico, far removed from any previous wheat centers • The highly specialized Hopi maizes are very different from any surviving primitive Indian corn
- 3. Contd., • The origins of crop plants are diffuse in both time and space • It is a failure to understand fully this principle that has led to much mis interpretation of Vavilovian theory • He freely admitted that he had too many centers for some crops, e.g. 5 for chickpea and 4 each for sesame, pea and lentil (Vavilov, 1949/50) • In effect, he was saying that Indian chickpeas originated in India, Ethiopian chickpeas originated in Ethiopia and Near Eastern chickpeas in the Near East; the ultimate origin of the crop itself was left for future investigation • This is reasonable and is comfortably in line with the concept of diffuse origins
- 4. Diffuse origins of Agriculture • The most definitive evidence for agriculture origins should come from archaeology • Techniques for the study of prehistory should ultimately resolve questions about where and when agricultural systems originated and describe their subsequent diffusion • There are still too many gaps in our information, but archaeological data gathered so far are very suggestive
- 5. • Most American, Canadian and European scientists perform at least some flotation to recover plant remains. The technique is not much used in Japan, USSR or some other developed nations • Activity has been especially intense in Europe, USA, Canada, Japan and some countries of the Near East • The Near East remains the best documented to date, and the evidence presented in table 1 transects a period of time when people were moving from the harvest of wild materials to the cultivation of domesticated plants
- 8. • The very early site for cultivated emmer at Nahal Oren is at present an anomaly but could be real, three spikelets were found sealed under a rock fall in Kebaran context • The morphology is that of a cultivated race according to Maria Hopf (one of the most distinguished and experienced archaeo botanists in the world) • At Murey bit and Tell Abu Hureyra large quantities of wild einkorn appear • This species is not found in the area today, but may have been present at the time range indicated • Cultivated plants were well established by the 8th millennium B.C. The next best record we have at present is that from Tropical America
- 10. • The pathway to agriculture in Mesoamerica at least was different from that in the Near East • Cultigens were added to the repertoire slowly, one by one. Early plant cultivation seems to have been more of a hobby than a serious pursuit of a food supply • In South America, the data are biased because of the focus of archaeologists on coastal sites • Data for Africa are too meagre for discussion. At present, the earliest remains of a fully domesticated African cultigen of finger millet were found in Gobedra rock shelter in Ethiopia - 4th millennium BC (Phillipson, 1977)
- 11. Harlan stated that • Because of the diffuse nature of origins, I have claimed that we will not and cannot find a time or a place where agriculture originated (Harlan, n.d.). • We cannot find a time because the processes went on over millennia, and we cannot find a place because activities of plant domestication were carried on simultaneously over vast regions around the world.
- 12. Diffusion • Diffusion of agriculture or tools and technique is thought to come about by two processes: Stimulus diffusion and Migration • In stimulus diffusion, the idea is transmitted from one area to another and the indigenous people take it up. Understandably, stimulus diffusion is difficult to prove for the prehistoric time range. Ideas do not leave their bones to be dug up. • In migration, the people with the tools and techniques simply move from one place to another. Migration can be demonstrated if the artifactual inventory is kept more or less intact.
- 13. Agricultural Diffusions • Agriculture is simply not easily diffusible from culture to culture and there are many examples of farming and nonfarming tribes living side by side without the nonfarming population taking up the practice (Berndt and Berndt, 1951; McCarthy, 1957). • The best example we have of agricultural diffusion is that of the Near Eastern complex of emmer wheat, barley, lentil, pea, etc. together with sheep, goats, cattle, and swine (optional) moving westward along the shores of the Mediterranean, north westward across the Balkans to the Danube, up the Danube and down the Rhine, eastward to the Indus Valley and southward to Ethiopia. • This diffusion is documented by hundreds of archaeological sites with recovered plant remains.
- 14. Main reason behind diffusion • We are not sure in to what sort of economies the farmers were migrating. • There is some evidence that the indigenous peoples were already practicing some sort of primitive husbandry of both plants and animals. • This is a phenomenon repeated many times in the historical time range.
- 15. Contd., • The diffusion of individual cultigens, however, is easier to follow. Wheat reached China in the second millennium BC; maize reached coastal Equador in the fourth millennium BC; squash reached the American Midwest in the fourth millennium BC, and so on. • Intraamerican diffusions are discussed by Pickersgill and Heiser (1977), for example. Plants domesticated in Mexico diffused to the Mississippi Valley one by one and not as a complex. • The local people were already practicing some sort of plant husbandry when the Mexican cultigens arrived. • The diffusion of a single crop or an unrealted set of crops rather than an integrated complex seems to be more a rule.
- 16. Archaeological evidence of the spread and use of some members of the leguminosae family • Cultivated types differ from the wild by non-dehiscent pods, more seeds per pod, thinner seed coat, bigger seed size. • But in archaeological material only the latter may show; with pea also a smooth surface. • From the oldest prehistoric sites in the Near East Lens and Pisum are documented together with the first cereals. Cicer and Vicia narbonensis/faba appear about the same time. Yicia ervilia was found somewhat more northernly (Turkey/Balkan). Lathyrus was apparently of minor or local importance.
- 17. contd., • The wild ancestors of these pulses - except of Vicia faba - are well known. Most of them were found in the "Fertile Crescent"; and their cytogenetic relation to the cultivated modern forms was proved by genetical analysis. • The primitive cultivars spread from this area to Africa (Egypt), all over Europe, and further into Asia.
- 18. a. Eisgm arvense from Early Bronze Age ARAD/Israel b. Lens culinaris from Late Bronze Age MANOLE/Bulgaria c. vicia faba from El Argar (=Early Bronze Age) CHIBANES/Portugal d. ervilia from Late Bronze Age MANOLE/Bulgaria e. Cigar Harietinum from Early Bronze Age ARAD/Israel Fig. 1. Seed remains (left) and seed from recent varieties (right) of cultivated pulses. (a) pea; (b) lentil; (c) broad bean; (d) bitter vetch; (e) chickpea. North, to the South and to the Far East took about 2-4 millennia local races will have developed.
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