Peopling of the Continents
PEOPLING OF THE CONTINENTS
From Africa, humans migrated to Asia and Europe and, later, settled the Pacific islands and the Americas. Successive waves of migration have covered the habitable world with self-sustaining settlements. The geographical patterns of peopling are the result of two closely related processes: migration and endogenous growth associated with contextual living conditions. Robust endogenous growth is seldom found in isolated and sparse settlements unless the population reaches critical levels of density that make the division of roles and functions and the emergence of agriculture possible. With the neolithic revolution–about 10,000 years ago in the Middle East and China, and later in the Americas–endogenous growth accelerated, providing an additional impetus for successive waves of settlement in empty or sparsely settled regions of the world. As early as 2000 years ago, with a total population of between 250 and 350 million, most regions of the world were well settled with populations expanding by natural growth rather than by migration.
The growth performances of the various continents and regions have differed widely during the last two millennia. In approximately 1500, the population of Europe was double that of Sub-Saharan Africa; in 1900 it was four times larger; and in 2000 the populations were nearly equal. In 1500 the Americas–according to William Denevan's 1992 estimate–had approximately the same population as Africa; in 1800 it was one-half Africa's size; and in 1900 it was larger than Africa's population by 50 percent. Migration flows and differential natural growth are the proximate determinants of these highly varied performances, but the remote determinants are much more complex and rooted in differential command of technology and knowledge, resilience of social texture, and environmental characteristics.
Oddly enough, Africa, the continent of humanity's origin, has the least understood demographic history. Over the last millennium, the population growth of sub-Saharan Africa was associated with the expansion of Bantu populations, sustained by the use of iron, and by the extension and intensification of agriculture in the tropical forests of Central Africa and in the savannas of East and Southern Africa. Coinciding with this expansion was the southward movement of Nilo-Saharan populations from the eastern part of the continent. The population of North Africa, which at the peak of Roman power matched the size of that in the Sub-Saharan region, fell to perhaps one-fourth of that amount by the middle of the last millennium.
There is a great deal of information available about the slave trade and the forced abduction of millions of Africans, who were taken mainly from the west coast of the continent and transported, in major part, to the Americas, beginning in the late-fifteenth century. The total number of people who were forcibly moved to the Americas is believed to be about 8 million between 1500 and the end of the trade in the mid-nineteenth century. Another flow, of lesser magnitude, followed Arab trading routes to the north. It is generally thought that the slave trade had little or no effect on the growth of Africa's population, which was approaching 50 million at the beginning of the relevant period. A strict Malthusian interpretation of these events is that the population drain might have improved the chance of survival of those remaining behind by lessening the pressure on resources, while the revenues of the slave trade improved the standard of living. But this view must be balanced by the fact that slaves were typically in the prime productive years of their lives, families were separated, and communities were deeply wounded. The negative demographic effects on the areas from which the slaves came must have been considerable.
The size of the population of the Americas at the time of the first European contact is a matter of controversy, with many ideological connotations. Influential estimates made by scholars in the last 50 years vary between a low level of 13 million by Angel Rosenblat in 1954 to a high of 113 million by Henry F. Dobyns in 1966, with more recent reassessments taking a middle course: 54 million according to William M. Denevan in 1992. However, the negative impact of contact and conquest is not in dispute: By the early seventeenth century the population had declined to just above 10 million and a sustained recovery took place only during the eighteenth century with the contribution of European and African immigration.
The steep decline in the century after the European arrival has been traditionally explained by the violent shift of power that ensued and the consequences of wars, forced labor, displacement, and violence. These were the ingredients of the black legend of the Conquest, first discussed in the writings of the settler-turned-Dominican friar, Bartolomé de Las Casas (1484–1566), and expanded to include anti-Spanish and anti-Catholic attitudes by later writers. Later revisionism, while raising the initial estimates of the indigenous population, attributes the main cause of the demographic catastrophe to diseases–such as smallpox, measles, or influenza–imported from Europe into a population with no immunity. However, the epidemiological explanation fails to take into account the complexity of the changes brought about by the European conquest and settlement. To assess the mix of factors that led to population decline or outright depopulation calls for careful analysis of each area and society. In the Greater Antilles, for example, local Taino Indians had almost disappeared by the mid-sixteenth century and were already much reduced in numbers by 1518 when the first epidemic of smallpox reached the New World from Europe. Earlier negative effects on survival and fertility may be traced to the economic displacement and confiscation of labor by the new masters, which eroded the standard of living in the local subsistence economy, the disruption of traditional social hierarchies, the fragmentation of families and clans, and the absorption of Taino women into the European reproductive pool. In other places, and particularly in the areas of densest settlement, it is likely that imported diseases were the principal cause of population decline.
Some population historians, including Sherburne Cook and Woodrow Borah, demonstrated that population decline was more severe in the areas with low density–for instance, in the coastal lowlands of the Gulf of Mexico–than in the more densely-settled plateaus and highlands–such as those making up the core of the Aztec empire. This argument, if correct, is at odds with the epidemiological explanation: The transmission of new pathologies would have been easier, and would have had deadlier effect, where the population was densely settled. Another nonepidemiological factor in depopulation must have been the displacement of native populations under the pressure of European settlement, as happened, for instance, along the coast of Brazil.
European populations thrived everywhere. The population of French origin in Québec in 1800, was seven times larger than the total inflow of immigrants from France up to that time; the population of Iberian and British origin was three to four times the cumulated immigration from their areas of origin. Compare this pattern of growth with the mere doubling of the European population from 1500 to 1800. European settlers had ample access to land; they found favorable climatic conditions and a more benign pathological environment; and plants and livestock imported from Europe flourished.
In the Americas as a whole, a cumulative total of some two million European immigrants, who had arrived by 1800, had grown into a population (not counting mestizos) of around seven million, equally divided between north and south. The population of European origin approached the size of the indigenous population, the descendants of the estimated 54 million of 1500. In contrast with the European immigration, the population of African origin (slave and nonslave) suffered heavy losses due to adverse living and working conditions, restrained family formation, and other consequences of slavery. In 1800 the African population in the Caribbean was perhaps 50 percent of the total inflow of enslaved people that arrived from Africa, while in Brazil the same population approximated the cumulated inflow. These two destinations accounted for 80 percent of the slave trade. A continuous inflow of slaves was needed in order to compensate the negative natural growth of the African population.
In the following century and a half, the population of the Americas increased rapidly due to the pressure of mass European immigration pushing the frontier of settlement westward and southward. Between 1840 and 1940, immigration accounted for 60 percent of natural growth in Argentina, 40 percent in the United States, and 20 percent in Brazil and Canada. Mexico, by far the most populous country of the Americas up to the eighteenth century, was the destination of only modest inflows of immigrants and slaves; Mexico was surpassed in population size by the U.S. in 1800 and by Brazil in around 1850.
The peopling of Europe is relatively well understood. In prehistoric times agriculturists from Asia Minor progressively migrated northwest into Europe, bringing new settlements and cultivation techniques and causing, or at least encouraging, the neolithic revolution there. The great blending of populations caused by migration from outside the continent increased with the fall of the Roman Empire and continued until the end of the ninth century when nomadic people, today's Hungarians, coming from the Euro-Asian steppes settled in the Carpathian Basin. Immigration continued to the open areas in the east of the continent and with the ebb and flow of Turks in the Balkans. Nevertheless, major immigration into Europe basically ended by the end of the Middle Ages.
The early centuries of the second millennium saw sustained population movement to the east of the continent, a settlement process that continued, in spite of the demographic decline caused by the Black Death in the fourteenth century, with varying rhythm until the nineteenth century. Much of this movement consisted of Germanic groups that gradually settled in territories east of the river Oder, which had been occupied by ethnic Slavs during the preceding millennium, and later in the southeast in territories taken back from the receding Ottoman Empire. The numbers of migrants were relatively small (perhaps a few hundred thousand), but improved technology, good organization and planning, and abundant land created conditions that both favored the natural growth of settlers and generated new waves of migration. In addition to this major eastern thrust, there were also lesser migrations in other directions: Spaniards and Portuguese toward the south, following the Reconquista of the Iberian peninsula (the fifteenth century expulsion of the Arabs); northward by the Scandinavians; and Slavs southward in Russia in search of more stable borders.
After two centuries of moderate but significant migration from Europe to the Americas, Iberian and British imperialists had established the political, economic, and demographic basis for mass migration. The availability of land in the Americas and to a lesser degree in Oceania, combined with an expanding demand for labor in these new societies, created the conditions for massive outflow from Europe. The industrial revolution and the acceleration of population growth in Europe pushed an increasing number of peasants out of their traditional occupations, making them candidates for emigration. Between 1846 and World War II, over 60 million Europeans emigrated, 50 percent of them from the British Isles and Italy; 60 percent of this flow went to North America, and another 25 percent to Latin America. (Many emigrants eventually returned to their home countries.) Another steady outflow–exceeding five million in total–was from European Russia to Siberia and Central Asia in the second half of the nineteenth century and the first half of the twentieth century.
In the first 15 years of the twentieth century the annual rate of European emigration exceeded three per thousand, one-third of the rate of natural increase. In spite of this drain, Europe accounted for about one-fourth of the world population by the onset of World War I, as compared to less than one-fifth in 1750. In part because of this drain, the Americas's share of the world population increased from 2.3 percent in 1750 to 11 percent in 1914.
The population of Asia is so large that growth of the largest countries has been mainly endogenous, migration playing only a minor role, at least in modern times. In China, with the Ming dynasty replacing the Mongol dynasty in the fourteenth century, the depopulated north was the destination of substantial migration from the Yangtze area. In the nineteenth century and at the beginning of the twentieth century, Chinese migrants went to other southeast-Asian countries–Malaysia, Indonesia, Indochina, Thailand–as well as to the Americas. Indian labor, after the end of the slave system, emigrated to places such as Natal in South Africa, Mauritius, and Trinidad. But the quantitative impact of these flows on the populations of origin was very small, and the decreased weight of Asia on world population, from around 66 percent in 1800 to 55 percent in 1900, is due to natural increase in Asia that was lower than was then prevailing in the rest of the world. Over the same period, the combined weight of Europe and of the Americas on world population increased from 23 to 36 percent, while that of Africa declined from 11 to 8 percent. During this period the West, in full demographic transition, reached the zenith of its weight in world population.
The Twentieth Century
In the twentieth century waves of migration were important locally but, with the steep drop in European emigration in the third decade of the century, changes in the distribution of population among the continents and regions of the world were mainly due to differences in natural increase. This rate declined in the West, with the nearing completion of its demographic transition, and soared in the other continents with the mid-century onset of their respective transitions. For the world as a whole, the number of migrants in relation to the total population has become relatively small: in the second half of the twentieth century the foreign born made up little more than 2 percent of the total population. By 2000, the weight of Europe had declined to 13 percent, about half the level it reached in 1900.
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