The Yale study was published in the journal Scientific Data.
Lead author Meredith Reba said researchers had a number of questions they hoped could be answered by mapping urbanization through history.
The most obvious question centered on agricultural evidence of early urban centers
. Were cities located in these areas the fastest growing and biggest historically? Did cities change their surroundings? And as a follow-up, have all large urban centers always been located in prime agricultural regions? If this is so, what does it tell us about future trends in the movement or location of urban centers?
To find out if they could answer their questions, Reba, and her colleagues digitized, transcribed, and geocoded over 6,000 years of urban data. For their dataset, according to the Yale website
, the authors used two principle sources: “Four Thousand Years of Urban Growth: A Historical Census” (1987), by historian Tertius Chandler, and “World Cities: -3,000 to 2,000” (2003), by political scientist George Modelski, which documents the world's most important cities during three eras of history (ancient, classical, and modern).
The two books are not widely available and the data in them is difficult to decipher because it is not in digital format. The new dataset has been digitized and is easily accessible, making the historical information available for examination by other researchers, including geographers, historians, archaeologists, and ecologists.
The questions the researchers wanted to find answers to involve much more than just knowing where past urban centers may have been located. The mapping process also gives us insight into environmental factors that influenced the shift in populations, as well as how climate may have played a role in development over the long term.
Some of us were taught in grade school that Mesopotamia was considered the "cradle of civilization." The dataset shows the global mean centers (GMC), or global city populations, shifted west from Mesopotamia over time, and additionally, GMCs have not remained constant.
If we were to apply the mapping to today's world, we would see that urbanization is continuing to shift in parts of the world due to environmental factors, internal strife, or disease. Reba says, "Outbreaks of disease, natural disasters, fires, and battles/wars can be marked by some population shifts in the dataset and are good examples of how a geographic environment can shape urban populations and population dynamics."
You could go so far as to say that urbanization is relevant to a range of disciplines, including geography, sociology, economics, urban planning, environmental health, and public health. Using all these disciplines provides an opportunity for sustainability with the “potential to use resources more efficiently, to create more sustainable land use and to protect the biodiversity of natural ecosystems,” according to the UN Population Fund
In the dataset, the authors are very clear as to the meaning of the locations documented: "The earliest records available are in the warmest colors (red), and are clustered around Ancient Mesopotamia. The latest ones on record are in blue. (To be clear, the map shows when the populations of cities started being documented, not when and where these cities were actually “born.”).