The history of of human civilisation is still far from complete, not so much because humanity has a future still ahead of it, but rather because large gaps exist in our knowledge of past cultures. On these and thousands of other  questions about the peoples and events that shaped civilisation, historians can only make educated guess. This is particularly true of the earliest civilisations.

Even these imperfect histories could not be written before the nineteenth and twentieth centuries. Although there were some ancient historians, their accounts dealt with the figures and events of their own time, relating to their own and few neighbouring societies.  The systematic search ad preservation and study of past civilisations did not yet yet exist, they had little or no idea about the true identity and achievements of the peoples that preceded them.

Only with the development of the science of archaeology in the past two centuries has the silent earth begun to release a torrent of information about the ancient civilisations. Until then scarcely anyone had conceived the notion that the dead past was everywhere around us, beneath our feet, waiting for resurrection. Since then along with the thousands of relics from the past, mighty monuments of human will and imagination has been unearthed, lost languages has been recovered, forgotten scripts has been read, . . . .

Besides these, some general, overriding historical realities have become apparent. one of the most important is that the earliest human societies often had a cultural impact on one another; and that their lifestyles, customs, and discoveries profoundly influenced and shaped later cultures and nations, which in turn, passed on the torch of civilisation. As scholar Gilbert Highet puts it:

"The history of one nation is unreal, the history of one civilisation is incomplete unless it also includes the impacts of the other nations and cultures upon it and describes their effects . . . Half of history is the history of distinct civilisations. The other half is the story of cross-culture conflicts and cross-culture fusions."