Archaeologists want to understand the physical and biotic environments that past human cultures colonized and lived in for a number of important reasons. For example, investigators who study prehistoric diets and land-use patterns know that the environment to a significant degree determines the type, quality, and abundance of wild plants and animals that hunters and gatherers can exploit and potentially take under cultivation and domesticate. Dramatic oscillations of climate and vegetation may result in fluctuations in the density and distribution of the resources, leading to dietary innovation and change. The technologies (milling stones, fishing gear, hunting traps, projectile points, various types of chipped stone tools) that are best used to procure plants and animals and turn them into food, clothing, shelter, and other utilitarian items may also depend on the types and density of resources available for exploitation.
Other major issues in archaeology that require good environmental reconstructions have to do with ancient migrations of humans from one area of the world to another, together with often related questions of human adaptations to coastal environments. In these cases, archaeologists must have good data on past fluctuations in sea level and other characteristics of marine environments. Rising and falling sea levels result in, respectively, a loss or exposure of land area, which, among other things, might affect the timing of human colonization of major landmasses along with the technology required to do so. For example, through detailed reconstructions of sea-level fluctuations during glacial advances and retreats, scientists now understand that when human populations settled the Australian continent from Southeast Asia probably by 40 000 years ago, consecutive expanses of deep water hundreds of kilometers wide separated northern Australia from the nearest land masses, and sophisticated use of water crafts was required. In contrast, the initial peopling of the Americas from northeastern Asia sometime before 15 000 years ago occurred over a large land bridge exposed by lower sea levels and did not require passage by boats over long stretches of deep ocean. Nonetheless, if archaeologists, prominently including Ruth Gruhn, who believe that early migrations followed nearshore coastal routes are correct, boats dodging glaciers and hopping from island to island around icy fjords would probably have been a necessary component of the original migrations from the Old World to the New, and down through the westernmost portions of North America.
The quality and quantity of resources that are typically important in the diets of human groups living on or near coastlines - such as various types of fish, shellfish, and sea mammals - also heavily depends on prevailing ocean temperatures and currents. These issues have perhaps been studied in the most detail along the Peruvian coast, where fine-grain reconstructions by Daniel Sandweiss and others of changes in coastal environments during the past 11 000 years, including the timing and effects of ENSO (El Nifio/Southern Oscillation) cycles that brought severe droughts or floods, have greatly increased understanding of the complex patterns of human coastal adaptations along this important area of western South America.
A palaeoenvironmental reconstruction may, therefore, deal with a wide variety of characteristics of past landscapes: vegetation, climate, topographic and hydrological features, specific landforms such as glaciers, lakes, and swamps, and still visible markers of human activity such as prehistoric irrigation ditches and canals. Table 1 Provides a brief guide to the kinds of studies carried out by various specialists, including archaeologists, that archaeologists rely on. These kinds of studies have long been carried out all over the world and as time goes on and more techniques
Most researchers involved with studying the pa-laeoenvironment use their accumulated data primarily to understand the past, not to inform present-day debates or predict what the future may hold. However, as it becomes more clear that reconstructions of the ancient world have direct relevance to managing in an intelligent way our present and future landscapes, environmental historians can increasingly share in the responsibility of developing informed environmental policies and mitigating future, detrimental global climatic and other changes. For example, what we have learned about the origins and antiquity of the planet’s current store of biodiversity (e. g., how the extreme Ice Age conditions of the past 2 million years impacted tropical and other landscapes), should allow conservation biologists to better model plant succession following major ecosystem disruptions, as well as to predict and pattern forest regeneration when planning regrowth programs.
Moreover, the documentation of the often considerable to sometimes profound impact of human populations on the vegetation and overall biodiversity of many past landscapes, discussed in detail below, has helped to make it clear that indigenous societies did not often practice strategies that conserved many of their resources. Many societies instead used their environments to the limit of their technology to attempt to ensure their short-term success. These facts remind us that in order to better preserve and protect remaining biodiversity we not only have to have better data from ecologists, foresters, and climate modelers; we, the anthropologists, have to straightforwardly assess past and present human behavior, its proclivities, and its goals.
Another possibly crucial area of insight into future global conditions, this time concerning the effect of increasing atmospheric CO2 on the European climate, has been provided by scientists called palaeo-oceanographers, who gather biological and physical data from the oceans and study their relationships to what happens over land surfaces. These scholars have learned that processes occurring deep in the oceans profoundly affect climate and vegetation over both nearby and distant continents. For example, it would be easy to assume that ever-higher amounts of atmospheric CO2 robustly predicted by climate modelers if fossil fuel injections into the atmosphere are not slowed considerably would lead to global-wide warming. However, studies of changes in the deep ocean circulation and how they affected the Earth’s climate during the final stages of the last Ice Age between 14 000 and 10 000 years ago, when the Earth was ‘warming’ considerably, show us this assumption might be a mistake with serious consequences for some highly populated and developed areas of the world. Palaeooceanographers using geochemical and other indicators have discovered that something they call the ‘North Atlantic conveyor’, part of a chain of ocean currents that brings warm water and air from the tropics to the far North Atlantic and heats much of maritime and continental Europe, was actually disrupted or halted completely by influxes of glacial meltwater and run-off from rivers as the Ice Age was ending. This was a major cause of the Younger Dryas, the temporary return to Ice Age conditions that affected much of the world between 11000 and 10 000BP.
What makes all of this very real for us today is that a recent study documented for the first time that the ocean conveyor may have slowed considerably during the last 30 years, presumably due to the same melting glacier and river run-off effects that caused climate reversal 11 000 years ago. Climate is a particularly dangerous thing for human populations to tamper with because it is nearly impossible to predict when a threshold for climate changes, such as those that involve ocean circulation, is close to being reached, and resulting shifts in temperature and precipitation tend to be quite abrupt. For example, palaeoclimate studies have shown that temperature can decrease by 10 °C (about 23 °F) in less than 30 years. If the conveyor belt breaks down or continues to slow, Europe may in the near future experience severely colder temperatures that could lead to significant socioeconomic disruptions. These examples show how understanding past environments and factors that controlled global change can help us to better plan for the future.
World History
