Theory:

Urbanisation started with the thriving of civilisations. Considering this, we can understand that the process of urbanisation in the world has a very long history. It is speculated that urbanisation began when a particularly prosperous and efficient village attracted the attention of other, less prosperous tribes who then attached themselves to the successful settlement.
Ancient Period
The urban centres started developing during the prehistoric period (before \(10000\) years). During this period, primitive man started domesticating plants and animals, i.e. agriculture and cattle rearing practices were started. So, they don't have to wander in search of food. This resulted in the development of permanent settlements. The fertile river valley regions with plenty of water for agriculture in Egypt, Greece and India gave rise to agrarian communities, which eventually formed the urban communities and urban centres.
 
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The boom in agriculture and the excess production of food grains due to it is the major reason for urbanisation. Ur and Babylon in Mesopotamia, Thebes and Alexandria in Egypt, Athens in Greece, Harappa and Mohenjodaro (Indus valley civilisation) in India were well-known prehistoric cities of the world.
 
During the two great colonising periods of the Greeks and Romans in ancient times, there was an increase in the number and size of urban centres. During the early \(7th century \)itself, many cities were found near the Aegean Sea. During the Greek colonising period, the expansion of trade encouraged the growth of towns and cities.
Together, India, China, and Nigeria are expected to account for \(35 %\) of the world’s urban population growth between \(2018 \)and \(2050\). India is projected to add \(416 \)million urban dwellers, China \(255 \)million and Nigeria \(189 \)million (World Urbanisation Prospects, 2018, Key facts).