Anthropology is the science which studies the humans in society, also, the relations between this society and the environment. Modern anthropology is a discipline inside the anthropology. It tries to explain man through his social and cultural environment.
When anthropology as a discipline is applied to modern societies there is a factor that generates a problem, time. We don´t have enough historical resources to size the real impact of situations, for example, climatic problems.
In ancient civilizations studies, we employ a diachronic method so as we can measure the evolution and progress of cultural and natural events. In the case we study of modern civilizations, the consequences of different situations aren't quantifiable, so the conclusions we can get are partial.
