Agricultural Origins: Old World

 The origin of agriculture began about ten thousand years ago. Seven centres of origin have been identified, four in the Old World and three in the New World. The oldest centre is in the Old World at the eastern end of the Mediterranean Sea extending through Syria, Turkey, Iraq and Iran. Two separate origins were located in China, one in the south along the Yangtze River and another in the north in the valley of the Yellow River. The fourth centre was in a band in Africa extending south of the Sahara. The transition was a gradual one in each separate case and the plants that were domesticated were distinctive of the particular region. The origin of agriculture can be looked upon as an evolutionary process in which the domesticated plants underwent substantial modifications. For the humans the transformation may also be looked upon as an evolutionary process but the changes have been largely cultural rather than physical. There is growing evidence that agricultural origins were not entirely restricted to the centres but occurred to varying degrees in other locations.

Agricultural Origins: Old World

INTRODUCTION

For most of their history, humans have been hunters and gatherers and only in the past 10,000 years has agriculture become the basis of food production. With- out farming, human population remained low, probably somewhere between 10 and 30 million and only the invention and spread of agriculture have allowed population to pass six billion and continue to grow.

For a long time, it was widely believed that the discovery of farming techniques was a unique invention in the mountainous region east of the Mediterranean Sea. Now, however, at least six other independent centers of origin are recognized and evidence is emerging that there may be others Four of the centers of origin are in the old world and these will be the topic of this article.

OLD WORLD CENTERS

The oldest center of origin in the old world is believed to be in the Near East in a band called the Fertile Crescent, extending from the eastern end of the Mediterranean Sea through Syria, Southern Turkey, Iraq, and Iran. The age of this center is believed to be 9000–9500 years, but there is growing support for an age of at least 10,000 years Wheat, barley, peas, and lentils were important crops, and sheep and goats were domesticated. Sickle blades for harvesting and grinding equipment were definitely in use. During the early part of this period, the climate was warming with minor oscillations after the last Ice Age.

From here agriculture spreads along the north coast of the Mediterranean to Europe and south to the Nile valley and Mesopotamia The second oldest center of origin appears to have been in southern China along the Yangtze River, and the age is believed to be around 8500 years. Rice was the main crop, but various other plants were cultivated, including water caltrop and foxnut. Another center of origin in China was independently established along the Yellow River in the north, a 1000 years later, around 7500 years ago. Here the original crops were millets and only much later was rice introduced to cultivation. The fourth old world center of origin occurred much later about 4000 years ago in a band, south of the Sahara Desert. Here sorghum, millets, and a different species of rice were the major crops domesticated. Further study of the origin of agriculture has increasingly led to the conclusion that the recognized centers are important, but that there is evidence of non-centered origins including New Guinea and southeast Asia.

The age of organic materials found in excavations has for many years been determined by measuring the emissions of beta particles from carbon 14 formed by cosmic rays acting on nitrogen. More recently, a new method using accelerator mass spectrometry mea- sures carbon 14 directly and can deal with very small quantities such as one seed. This technique has led to the correction of a number of dates arrived at by the older method.

THE TRANSITION TO AGRICULTURE

The transition from hunting and gathering to agriculture was a gradual one, which occurred over a long period of time and there still remain groups that have not adopted this method. The study of these people such as the Kung Bushmen in South Africa and the aborigines in Australia has given some evidence of the pre agricultural human culture. These people keep their population level down and generally do not have permanent settlements. Rather they visit a series of sites where their foods can be obtained on a regular basis. The transition to agriculture is believed to have been a gradual one, often with just one or two plants cultivated, while the remainder of the diet was collected in the wild.

There is evidence of an extended transitional or tending stage in which crops were not planted, but natural stands were protected from herbivores, cultivated and even, in some cases, provided with water by diverting natural flows. This was a kind of agroecology, and, in some cases, appears to have drastically modified the natural ecosystem. Along with this transition went storage facilities, processing equipment, and the establishment of territorial rights. There is some evidence of the response of such plants to this treatment, but they were not converted into cultivated crops.

THE ESTABLISHMENT OF AGRICULTURE

The beginning of actual cultivation has been a gradual process over an extended time period. It appears to have been a natural evolution motivated by convenience or the need for security. Some plants were preadapted to cultivation by their natural properties and may have become established on refuse heaps from discarded plant material.

This process has been referred to as a revolution, but it was much more of an evolutionary phenomenon. It was in fact a coevolution of the humans and the plants that they domesticated. With the establishment of agricultural planting and harvesting, the process of human selection came into play and as the plants became domesticated, their properties changed substantially. Certain of the features of wild plants were progressively eliminated naturally by the human practice of cultivation. Wild plants tend to have a seed dormancy phenomenon in which germination is extended over a period of time, several years in some cases. This trait was eliminated automatically by agricultural practices. Wild plants tend to scatter their seed or fruits when ripe over a period of time, but cultivation selects out this trait, and the seeds and fruits tend to be retained on the plant. Many plants that were perennials in the wild were converted to annuals, and the tendency to ripen uniformly was developed. In addition, the role of deliberate human selection must have affected other qualities such as size, productivity, texture, loss of toxic or distasteful substances, and the enhancement of flavors.

On the human side, the evolutionary change was more a behavioral one than a physical one. The human pattern of existence changed, as people became dependent upon the plants that they cultivated. The introduction of cultivation increased the productivity of the land and allowed population to grow. In time, urbanization appeared with division of labor, as food could be supplied by a portion of the population, and the remainder could develop other skills. Unlike the domesticated plants, there were few physical changes in the human population except for some dietary peculiarities that developed in certain groups.

THE DOMESTICATION OF CROPS

Many important crop plants now have widespread distribution and their actual origin has sometimes been difficult to trace. Wheat, which today is distributed around the world, had its origin in the fertile crescent at the eastern end of the Mediterranean. Wild einkorn was domesticated 9500 years ago, or even earlier, and became a cultivated crop. It is a diploid species, i.e.,it has two sets of chromosomes, one from each parent and contains one kernel in each unit of the inflorescence. The other very ancient domesticated wheat is emmer, which is a tetraploid species with four sets of chromosomes. It arose as a hybrid in the wild, doubled the chromosome number, and was domesticated at about the same time as einkorn. Modern bread wheat, which is a hexaploid with six sets of chromosomes and also a hybrid, probably arose spontaneously about 8000 years ago. This wheat threshes cleanly and contains gluten, which gives it good raising properties in bread making. Today there are more than 20,000 cultivars of bread wheat alone.[4] Barley is another cereal crop that had its origin in the Near East and has been in cultivation as long as wheat and possibly even longer. It was in fact the chief cereal of the Near East until it was supplanted by the tetraploid wheat. Rice, which is the major cereal of southern Asia, thrives in a hot, moist climate and is usually grown in flooded paddies. Traditionally in Asia, it has been cultivated by sowing in seed beds and transplanting by hand and is also weeded and fertilized. The harvesting is also accomplished by hand labor. However the cultivation of rice can be mechanized and this has occurred in many places. Evidence indicates that it was first domesticated in the Yangtze River valley around 8000 years ago, and the wild ancestor is not entirely clear. The cultivated rice species is not known in the wild. The rice cultivated traditionally in Africa, south of the Sahara, is a different species, although the Asian variety has now been introduced. More than 16,000 varieties of cultivated rice have been identified around the world and these are mostly diploid The independent origin of agriculture in the Yellow River valley in North China occurred around 7500 years ago, a 1000 years later than its occurrence in South China, and was based on millets. Rice was introduced only later after contact with South China was established.

Although agriculture spreads widely from the Near Eastern center of origin, it did not apparently spread across Africa, south of the Sahara Desert. Here agriculture was based on sorghum, which is a relative of maize, species of millets, and a type of rice entirely different from the Asiatic species. Agriculture arose in a broad sub-Saharan band about 4000 years ago.

In addition to the cereals, which were domesticated, legumes or members of the pea family have been of great importance, because they provide excellent sources of protein, which is deficient in cereals. The unripe pods or the mature seeds contribute protein to the diet. They are valuable also because their roots contain nodules in which symbiotic bacteria fix nitro-gen from the atmosphere, which is released into the plant cells and converted into nitrogenous compounds. Among the important associated plants of the old world are lentils, one of the oldest cultivated plants from the Near East, and peas, which are found in the same sites. The broad bean or faba bean is a plant of the Mediterranean region, which was cultivated at least 4000 years ago and possibly much longer. Also from the Near East is the chick pea or garbanzo, which was cultivated by the ancient Egyptians, Greeks, and Israelites, but today 80% of the crop is produced in India.

Another legume of ancient use in Asia is the soybean, which originated in central China. Its use goes back 3000–5000 years in time. This plant is still of significant importance in China, but the major production has now shifted to U.S.A. and South America. It is an excel- lent food source but also has many industrial uses

CONCLUSIONS

As further investigation continues, there may be other centers of origin of agriculture in the old world and in fact there is already evidence suggesting this fact. The independent origin in a number of separate locations widely spaced in time suggests that the process was a natural development of human needs and intellectual capacity. This origin had a profound effect on human history and the present population of the earth could not exist without this foundation underlying it. It is an interesting question to consider how long human population growth can continue on this planet, with agriculture as the chief basis of its food supply.