There is a general consensus among mainstream anthropologists that humans first emerged in Africa about two million years ago. Since then we have spread throughout the world, successfully adapting to widely differing conditions and to periodic cataclysmic changes in local and global climate. The many separate societies that emerged around the globe differed markedly from each other, and many of these differences persist to this day.
As well as the more obvious cultural differences that exist between peoples, such as language, dress and traditions, there are also significant variations in the way societies organize themselves, in their shared conception of morality, and in the ways they interact with their environment. It is debatable whether these differences are merely incidental artifacts arising from patterns of human migration or whether they represent an evolutionary trait that is key to our success as a species. By analogy with biodiversity, which is thought to be essential to the long-term survival of life on earth, it can be argued that cultural diversity may be vital for the long-term survival of humanity; and that the conservation of indigenous cultures may be as important to humankind as the conservation of species and ecosystems is to life in general.
This argument is rejected by some people, on several grounds. Firstly, like most evolutionary accounts of human nature, the importance of cultural diversity for survival may be an un-testable hypothesis, which can neither be proved nor disproved. Secondly, it can be argued that it is unethical deliberately to conserve "less developed" societies, because this will deny people within those societies the benefits of technological and medical advances enjoyed by those of us in the "developed" world. Finally, there are some people, particularly those with strong religious beliefs, who maintain that it is in the best interests of individuals and of humanity as a whole that we all adhere to the single model for society that they deem to be correct. For example, fundamentalist evangelist missionary organisations such as the New Tribes Mission actively work to reduce cultural diversity by seeking out remote tribal societies, converting them to their own faith, and inducing them to remodel their society after its principles.
Cultural diversity is tricky to quantify, but a good indication is thought to be a count of the number of languages spoken in a region or in the world as a whole. By this measure, there are signs that we may be going through a period of precipitous decline in the world's cultural diversity. Research carried out in the 1990s by David Crystal (Honorary Professor of Linguistics at the University of Wales, Bangor) suggested that at that time, on average, one language was falling into disuse every two weeks. He calculated that if that rate of language death were to continue, then by the year 2100 more than 90% of the languages currently spoken in the world will have gone extinct.
There are several international organisations that work towards protecting threatened societies and cultures, including Survival International and UNESCO. The UNESCO Universal Declaration on Cultural Diversity, adopted by 185 Member States in 2001, represents the first international standard-setting instrument aimed at preserving and promoting cultural diversity and intercultural dialogue.
The EC funded Network of Excellence "Sustainable Development in a Diverse World" SUS.DIV builds upon the UNESCO Declaration to investigates the relationship between cultural diversity and sustainable development.