People are living in closer quarters, too: After centuries of migration in search of work or a better living, 51% of all human beings now live in cities or slums.
By repeatedly repulsing Mongol raiders in the 13th century, the sultanate saved India from the devastation visited on West and Central Asia, setting the scene for centuries of migration of fleeing soldiers, learned men, mystics, traders, artists, and artisans from that region into the subcontinent, thereby creating a syncretic Indo-Islamic culture in the north.
The crags and escarpments of the Afghan landscape loom on the periphery of Nickelsberg's images, as do the faces of Afghans, of every hue and shape, living testaments to the centuries of migrations that have swept over the country.
Like many Western towns, it is the mottled product of a century of migration.
The large ethnic-Korean population makes it relatively easy for them to blend in, and, after a century of migration across the border, some have relatives in China.
But after half a century of migration from the Andean highlands, 70% of Peru's 26m people, most of its industry and its booming export agriculture are all crammed into the narrow coastal desert to the west of the watershed.The bigger problems are poorly run state-owned water companies, and a collapse in public investment.
Split across two modules, and including collections from 26 archives, libraries and museums, Migration to New Worlds brings together the movement and memories of millions across two centuries of mass migration...
All of these factors sharpen the longstanding religious divide that runs along the southern edge of the Sahel, 700 miles north of the equator – the tenth parallel where, thanks to geography, weather and centuries of human migration, most of North Africa's 500 million Muslims meet the 500 million Christians of sub-Saharan Africa.
(3) Since these stories have been accumulated through centuries of constant migration, they provide an unrivalled body of "clinical" material for studying the processes by which popular tales in fact travel and are transformed.
Both parents need to be carriers of the recessive MC1R gene in order for a child to be a redhead, so I wondered whether it had been passed down and across through centuries of human migration, the slave trade and even Irish/Scottish indentured servitude in the British Caribbean in the 17th century.
