Plant propagation is a discipline within the field of agriculture in which plants, selected for specific traits, are multiplied so as to conserve the selected trait from generation to generation.
"The propagation of plants is a fundamental occupation of humankind. Its discovery began what we now refer to as civilization and initiated human dominion over the earth. Agriculture began some 10,000 years ago when ancient peoples, who lived by hunting and gathering, began to cultivate plants and domesticate animals. These activities centered around stable communities, and people began to select and propagate the kinds of plants that provided a greater and more convenient supply of food and perhaps other products for themselves and their animals. Once this process began, humans could remain at the same site for long periods of time, thus creating stable centers of activity that eventually would become cities and countries."
Hartmann, H.T., D.E. Kester, F.T. Davies, R.L. Geneve (2002). Plant Propagation: Principles and Practices. 7th Ed. Prentice Hall, New Jersey.