As our narrative suggests, anthropologists are interested in the natural environment, the way humans have related to the natural world over time, and how this relationship shapes various cultures. Anthropologists consider how people in different cultures understand and use the various elements of nature, including land, water, plants, animals, climate, and space. They show how people interact with these elements of nature in complex ways. Archaeologists working in prehistoric sites all over the world have documented how prehistoric people understood celestial objects and used them to navigate their waterways, create calendars and clocks, regulate farming activities, schedule religious ceremonies, and inform political leaders. This area of study is called archaeoastronomy. In Chaco Canyon in the American Southwest, archaeologists have discovered that buildings in the major settlement areas were aligned so that certain windows would provide perfect vantage points to view the sun and moon at pivotal times of the year, such as solstice and equinox. The Sun Dagger, consisting of two whorl-shaped petroglyphs (stone etchings) on Fajada Butte, is precisely positioned under a rock crevice so as to indicate the solstices and equinoxes when the sun shines through the crevice. Unfortunately, tourist foot traffic at the site has altered the width and direction of the crevice so that the Sun Dagger no longer marks these celestial events accurately. Figure 1.5 The Sun Dagger at Fajada Butte (credit: National Park Service/Wikimedia Commons, Public Domain) The people of Chaco Canyon may have been particularly attuned to the features of their environment as they constructed their complex civilization in the challenging environment of the high desert. With scarce rainfall and brief growing seasons, their survival depended on accurate identification of opportune planting and harvesting times. With the onset of a 50-year drought, farming became more and more precarious. Eventually, the ancient peoples of Chaco were forced to abandon the area. Some anthropologists study how people interact with the plants in their area. The field of ethnobotany examines how people in different cultures categorize and use plants for food, shelter, tools, transportation, art, and religion. Ethnobotanists also conduct research on plants used in healing to discover the relationship between cultural practices and the pharmaceutical properties of these plants. Some examine the cultural use of psychoactive plants such as mushrooms and peyote in religious ritual. For instance, anthropologist Jamon Halvaksz studied the controversial use of marijuana among youth in New Guinea (2006). Young people told Halvaksz that marijuana helped them work harder, overcome shame, and understand ancestral stories. Critics of the practice told Halvaksz that marijuana dried the blood of people who used it, making their offspring weak and feeble. Marijuana use has generated similar controversies in other countries, including the United States, with some arguing that the drug provides relaxation and pain relief while others claim it interferes with cognitive abilities and motivation. Our relationship with nature is reciprocal. Nature shapes humanity, and humanity shapes nature. Exploring how nature shapes humanity, anthropologists speculate about how aspects of the environment have shaped the emergence and development of human biology, such as our ability to walk, the shape of our teeth, and the size of our brains. Dramatic climactic shifts over the past several million years have forced periods of rapid biological and cultural adaptation, resulting in new hominin species and new skill sets such as language and toolmaking. In more recent archaeological time periods, environmental characteristics have shaped religious beliefs, gender relations, food-getting strategies, and political systems. Environmental forces can trigger the beginning or the end of a society. Some archaeologists study how natural events such as volcanic eruptions and droughts have led to mass migrations and the collapse of empires. Our reciprocal relationship with nature also works the other way around; that is, humans shape nature. Our environments are shaped by the food-getting methods of our societies as well as the way we acquire and trade resources such as oil, natural gas, diamonds, and gold. Many anthropologists explore how contemporary ways of life change the natural world at local, regional, and global levels. Farming dramatically impacts ecosystems with the clearing of prairies, wetlands, and forests. Fishing can deplete certain species, changing the whole ecosystem of rivers and coastal waters. Responding to population pressures, people construct dams to channel water to emergent cities. The redirection of water transforms regional ecosystems, turning wetlands into deserts and deserts into resource-hungry cities. Scholars use the term Anthropocene to describe the contemporary period of increasing human impact on the ecosystems of our planet. Large-scale pollution, mining, deforestation, ranching, and agriculture are causing dramatic environmental disruptions such as climate change and mass extinction of plant and animal species. Many anthropologists are studying these problems, focusing on how people are working locally, regionally, and globally to promote more sustainable ways of living in our natural world.