The Human Past The Human Past The Human Past The Human Past
The Human Past The Human Past The Human Past The Human Past
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Chapter 19 - The Human Past: Retrospect and Prospect
Learning Objectives

After reading this chapter, students should be able to:

    understand the ways in which knowledge of the past can give insight into current problems

    connect past issues of population increase with demographic problems experienced today

    understand the positive and negative consequences of population growth, farming, and biological exchange

    trace the development from subsistence intensification, to population increase, to specialization, to social and economic complexity

    discuss human impacts on the environment

    describe the human struggle to adapt to and cope with climatic change

    explain the complex interactions of the Columbian Exchange

    characterize the ways in which archaeology can contribute to understanding past and present

The text has described the development of human societies over 2.5 million years, based on archaeological evidence and supplemented by written records in historic periods, since archaeology does not stop when writing appears. Whether prehistoric or historic, archaeology informs our understanding of human conditions and social practices up to the present day and places recent events in long-term perspective through four specific themes.


After the Ice Age, only a few million people inhabited the earth; today there are 6 billion, and the number is still growing, thanks to medical advances. This dramatic growth, especially since AD 1500, due to climatic stability and the development of social and economic mechanisms capable of supporting high population densities. The challenge of demographic increase is extracting more food from the environment, first through increasingly sophisticated hunting and gathering, second, through the development of agriculture. The process was gradual, first with locally available plants and animals, rain-fed cultivation, and simple technology. When animals were domesticated (in most regions) they were used for traction and transport, milk or wool, wealth, and as a meat source. Farming was highly varied due to very differing environmental conditions. Sedentary settlements almost always became the ultimate residence pattern.

Agriculture also had its down side: the health of early farmers was poorer than hunter-gatherers due to a narrower range of foods and dietary deficiencies. Tooth wear from grindstone grit was problematic, as was weather and crop failure. Increased incidence of infectious disease resulted from a larger reservoir of human hosts, crowded together with each other and domestic animals, whose diseases mutated into human forms, especially in the Old World, a process that continues today.

In long-term perspective, the most serious issues relate to the agricultural basis of demographic growth, which continues today, supported by increasingly intensive and industrialized farming.


Intensification of food production was achieved by breeding new, more productive crops or livestock, and devising new methods and technologies of cultivation, such as fertilizing with manure, shortening fallow periods, irrigation, and terracing.

With larger populations came growing social and economic complexity. Inequalities of wealth and status led to the rise of hierarchical societies, including the state societies or "civilizations."

Communities and individuals became more specialized. Some engaged in farming while others, i.e. metalworkers in a state society, could depend on others to support their needs: miners and traders to provide raw materials, farmers and administrators to organize and supply their food, market sellers for other needed commodities, scribes to record transactions.

The unprecedented size and food requirements of such early, complex urban populations placed heavy demands on agriculture, and in turn, on a vulnerable environment: irrigation systems could cause soil salinization and loss of fertility; forest clearance led to erosion. These problems are still with us today: intensive agriculture; degradation of rainforest from logging; or river flows crippled by diversion for irrigation.


Early farmers may never have traveled very far, relying on traders or down-the-line exchange for contact with distant places. Most long-distance human movement ended once the initial stages were complete, as in colonization events. Within the past 2000 years patterns of contact have remained active and become increasingly global in recent decades.

One consequence has been biological exchange, as domestic plant and animal species, in particular, became globally widespread: Eurasian cattle and sheep thrive in South Africa, New Zealand, and North America, while Mesoamerican maize is grown in Europe and sub-Saharan Africa. This pattern accelerated with the European explorations of the 15th and 16th centuries. Imported crops benefited some agricultural systems while damaging others.

Much deadlier was the exchange of human diseases. Ancient Eurasian populations suffered many epidemics recorded in historic documents. Most tragic of all such exchanges was the series of epidemics spread to the Americas by European invaders, who, through exposure to these diseases, developed a certain level of immunity. Native peoples of the Americas had few domestic animals, few infectious diseases, and thus no such immunity. Native American diseases had little impact on Europe. The imbalance of the "Columbian Exchange" was a major factor shaping the last 500 years of human history.


Rapid demographic growth over the past 12,000 years illustrates successful adaptation to postglacial environments, with their more clement conditions and much greater stability. There have been significant deviations within this pattern. At around 6200 BC, evidence from ice cores shows a sharp, severe cold phase that persisted for 200 years, when glacially-fed Lake Agassiz (part of the present Great Lakes area) broke through to the North Atlantic, where cold fresh water halted the Gulf Stream.

A more recent, less severe episode is known as the Little Ice Age, c. AD 1300-1850, when western Europe and eastern North America experienced severe winters, higher rainfall affected tropical Africa, and monsoon changes occurred in the Indian Ocean. The causes are still uncertain.

There is no reason to believe that the mechanism behind the long-term cycle of ice ages has ceased to operate. Ice ages recur every 100,000 years, generally related to subtle changes in the earth's orbit around the sun. The present warm phase is really an interglacial, not "postglacial." Some argue that human interference with the environment, by raising temperatures, may forestall a new ice age. Others worry that global warming and melting ice-sheets threaten to halt the Gulf Stream once again, which could be rapid and catastrophic. Clearly, human societies remain at the mercy of climatic changes for which their own activities may be partly responsible. Coping with such changes has been a key feature of the human past; it will remain so into the foreseeable future.

Key words and terms Chapter 19

development of human societies over the past 2.5 million years best seen through archaeology combined with later written records

ability to view recent events in the perspective of the long-term development of humanity

four specific themes can be seen through time, and link past event with insight into present: demographic increase, intensification and degradation, biological exchange, climate change and human society

population rise
climate stability
social and economic coping mechanisms
methods of extracting more food from the environment
hunting and gathering intensification
sedentary settlements
development of agriculture
intensification of agriculture
drawbacks of agriculture: diet, health, disease, risk
further population increase
agricultural productivity
inequalities of wealth and status
hierarchical societies
economic specialization
heavy demands on agricultural systems
dependence on fragile or unreliable systems
environmental impacts: salination, loss of fertility, erosion
biological exchange: travel, trade, exploration, colonization
domestic plant and animal species
human diseases
size and crowding of human communities
disease epidemics
the "Columbian exchange"
postglacial climate more clement and stable
climate deviations
Lake Agassiz transgression at around 6200 BC
halting of the Gulf Stream
two centuries of severe cold in global climate
the Little Ice Age, c. 1300-1850
variously severe winters, drought, higher rainfall, monsoon disruptions
recurrence cycle of ice ages
interglacial vs. postglacial
human interference of raising temperatures may forestall a new ice age
global warming threatens to halt the Gulf Stream again within a few decades
human societies remain at risk from climatic changes

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