ABSTRACT
Nonstates and states have historically affected local environments in dissimilar ways. Nonstate societies sometimes decrease and sometimes increase diversity in their local environments. Humans—more generally, the genus Homo —have been transforming nature for thousands of years, affecting the Earth's landscape wherever they have lived. Humans are rather ‘untidy' creatures, and they tend to leave behind evidence of their presence. Members of different societies interact with the environment in different, often culturally determined ways. Some societies contribute to local species diversity by creating many small habitats that favour the growth of distinctive organisms. Humans lived without domesticates for at least 140,000 years. The Pleistocene overkill hypothesis implicates mobile bands of hunters and gatherers in the extinction of megafauna. Greenhouse gases (GHGs) in the atmosphere have been increasing significantly since the beginning of the Industrial Revolution about AD 1800.
