Diffused centres of Origin - Diffusion in agriculture- stimulus diffusion and migratory diffusion

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.

19. THANK YOU