(i) Since ancient times, human societies have become more interlinked through trade and travel. In the past traders, travellers, priests and pilgrims travelled vast distances in search of knowledge, opportunity spiritual fulfilment or to escape persecution.
(ii) They carried goods and money to other lands. Similarly brought back goods and precious metals which were not available in their countries- commercial exchange thus was established.
(iii) These visits also led to the exchange of ideas, values, skills and techniques of production or creative talents.
(iv) Food habits and knowledge of growing a special crop too travelled with them.
(v) Travellers even carried germs and diseases.The incidence of long distance spread of germs of various diseases may be traced to 7th century. By 13th century it became an unmistakable link.