environment is arid or humid. However, when a single continent is divided into
different regions, we take into account some additional factors in determining
the regions. For example, in determining whether a city belongs to monsoon Asia
or the mid-latitude arid region, we consider the main crops grown, as the focus of the
former region is rice and the latter is wheat, based on the Köppen climate classification. When examining whether a city belongs to the mid-latitude arid region or
upper Eurasia, we classified the cities facing the Mediterranean Sea as the
mid-latitude arid region if the climate is regarded as humid under Köppen’s classification. In determining the division between the sub-Saharan Africa and the
mid-latitude arid regions, the existence of a modern state facing the Mediterranean
Sea is a conclusive factor indicating that a city belongs to the mid-latitude arid
region, as well as the history of the city or area. Thus, on this basis, Sudan is included
in the mid-latitude arid region, and South Sudan is included in the sub-Saharan
Africa. Again, in the division between Latin America and the North America and
Oceania region, the modern state is the conclusive factor, which results in adoption
of the border between Mexico and the USA as the dividing line.
We divided the eras prior to 1900 into the six eras discussed above, i.e., (1) the
early ancient era from 3700 to 1001 BCE, (2) the late ancient era 1000 BCE to
299 CE, (3) the early medieval era from 300 to 999, (4) the late medieval era from
1000 to 1499, (5) the premodern era from 1500 to 1799, and (6) the modern era from
1800 to 1900. Based on these six eras, the maximum value of each city’s population
in an era is regarded as the value of that era based on five population groups above,
and the number of cities is counted by six regions (Table 5.1).
After 1950, we use the UN population data for agglomerations over 300,000
people for 1950, 1980, 2000, 2015, and 2035. We use a similar method to that used
for cities before 1900 as the number of cities is counted based on three population
groups (focusing on populations over 1 million) for the six regions. The results are
shown in Table 5.1 and discussed in detail in the following.
5.3.2 Urban Populations Before 1900
We regard communities with above 10,000 persons as cities for the following
reasons. Before 3700 BCE, some agglomerations of populations over 10,000 are
reported in some places (Harper 2013). However, our hypothesis is that the city
originated in the Sumer civilization in Mesopotamia, and many Sumerian cities had
populations above 10,000 from 3700 BCE onward. Furthermore, Eridu, Uruk, and
Larsa, which are considered the first examples of cities in Mesopotamia, had
populations of 10,000 people in 3700 BCE. Cities with above 10,000 inhabitants
arose in the mid-latitude arid region, and we find that there were 100 such cities over
the entire early ancient era until 1000 BCE. In this era, an early example from
monsoon Asia region is Sanxingdui, in China, in 1500 BCE. Four settlements in
Ukraine, in upper Eurasia, that existed before 3700 BCE are regarded as agglomerations of population, although they differed from urban civilizations. In the late
5 Regional Diversity and Sustainability of Megacities in Global Historical. . .
77
different regions, we take into account some additional factors in determining
the regions. For example, in determining whether a city belongs to monsoon Asia
or the mid-latitude arid region, we consider the main crops grown, as the focus of the
former region is rice and the latter is wheat, based on the Köppen climate classification. When examining whether a city belongs to the mid-latitude arid region or
upper Eurasia, we classified the cities facing the Mediterranean Sea as the
mid-latitude arid region if the climate is regarded as humid under Köppen’s classification. In determining the division between the sub-Saharan Africa and the
mid-latitude arid regions, the existence of a modern state facing the Mediterranean
Sea is a conclusive factor indicating that a city belongs to the mid-latitude arid
region, as well as the history of the city or area. Thus, on this basis, Sudan is included
in the mid-latitude arid region, and South Sudan is included in the sub-Saharan
Africa. Again, in the division between Latin America and the North America and
Oceania region, the modern state is the conclusive factor, which results in adoption
of the border between Mexico and the USA as the dividing line.
We divided the eras prior to 1900 into the six eras discussed above, i.e., (1) the
early ancient era from 3700 to 1001 BCE, (2) the late ancient era 1000 BCE to
299 CE, (3) the early medieval era from 300 to 999, (4) the late medieval era from
1000 to 1499, (5) the premodern era from 1500 to 1799, and (6) the modern era from
1800 to 1900. Based on these six eras, the maximum value of each city’s population
in an era is regarded as the value of that era based on five population groups above,
and the number of cities is counted by six regions (Table 5.1).
After 1950, we use the UN population data for agglomerations over 300,000
people for 1950, 1980, 2000, 2015, and 2035. We use a similar method to that used
for cities before 1900 as the number of cities is counted based on three population
groups (focusing on populations over 1 million) for the six regions. The results are
shown in Table 5.1 and discussed in detail in the following.
5.3.2 Urban Populations Before 1900
We regard communities with above 10,000 persons as cities for the following
reasons. Before 3700 BCE, some agglomerations of populations over 10,000 are
reported in some places (Harper 2013). However, our hypothesis is that the city
originated in the Sumer civilization in Mesopotamia, and many Sumerian cities had
populations above 10,000 from 3700 BCE onward. Furthermore, Eridu, Uruk, and
Larsa, which are considered the first examples of cities in Mesopotamia, had
populations of 10,000 people in 3700 BCE. Cities with above 10,000 inhabitants
arose in the mid-latitude arid region, and we find that there were 100 such cities over
the entire early ancient era until 1000 BCE. In this era, an early example from
monsoon Asia region is Sanxingdui, in China, in 1500 BCE. Four settlements in
Ukraine, in upper Eurasia, that existed before 3700 BCE are regarded as agglomerations of population, although they differed from urban civilizations. In the late
5 Regional Diversity and Sustainability of Megacities in Global Historical. . .
77