Chapter Summary and Key Concepts

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.

Chapter Summary

The book 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 almost 7 billion, and the number is still growing, thanks to medical advances. This dramatic growth, especially since ad 1500, is connected with 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.

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 were shortages caused by 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.


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, e.g. 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. 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 travelled 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. 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.


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.

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. 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 Concepts

  • population rise
  • climate stability
  • social and economic coping mechanisms
  • hunting and gathering intensification
  • sedentary settlements
  • development of agriculture
  • intensification of agriculture
  • drawbacks of agriculture: diet, health, disease, risk of crop failure
  • population increase
  • agricultural productivity
  • inequalities of wealth and status
  • hierarchical societies
  • economic specialization
  • dependence on fragile or unreliable systems
  • environmental impacts: salination, loss of fertility, erosion
  • biological exchange: travel, trade, exploration, colonization
  • size and crowding of human communities
  • disease epidemics
  • the “Columbian exchange”
  • postglacial climate more clement and stable
  • climate deviations
  • Lake Agassiz
  • halting of the Gulf Stream
  • the Little Ice Age, c. 1300–1850
  • recurrence of cycle of ice ages
  • interglacial vs. postglacial