On a cultural evolutionary view, the natural environment has less to do with invention -- individual or social originality is totally random -- but more to do with innovation -- the transmission of invention. Thus, to test this view, we are interested in those features of the natural environment that influence the probability that individual people will transmit their behavior traits to other people. In many cases, this probability is largely determined by how long the potential transmitter lives or survives. Thus, we focus primarily on those features of the environment that influence the probability of individual people's surviving to a certain age.
How long individual people live (assuming air is constantly present) is largely determined by the presence in their local environment of:
Water is obtained from surface and ground water sources as well as directly from precipitation. Ambient temperature is simply the atmospheric temperature near the ground surface. People's food supply is determined by the relative abundance of wild plants and animals suitable for human predation. This is determined proximately by seasonal patterns of temperature and soil moisture content which, in turn, depend on seasonal rainfall and surface temperature, soil conditions and ground water.
Climatic and geologic features are not completely unrelated. For example, soil conditions are determined, in part, by underlying (literally) geologic features and, in part as well, by climatic conditions over time.
During the time that people have been present, the earth's climate has experienced significant changes on a world wide or global scale. These global climatic changes (and their regional and local manifestations) have played a major role in the evolution of human technology and social organization.
Changes in the surface geologic environment -- changes in the character of soils, anthropogenic depletion of resources such as petroleum and ground water -- have also played (and continue to play) a role. However, unless they are altered by climate and human activity, geologic features (on the time scale that concerns us) remain a relatively fixed feature of the natural environment.
From a global perspective, within the time period of human activity, most significant environmental changes are climatic. Relatively fixed, surface geological features operate to determine specific regional and local effects of these global climatic changes. Thus, at the global level, we focus a discussion of environmental change on climatic change. As we come narrow the focus to specific geographic regions (e. g. Mesoamerica) and locations (e. g. the Valley of Oaxaca) we will focus our discussion of climate to these regions and connect relate it to surface geologic features.
