Cultural diversity is the variety of human societies or cultures in a specific region, or in the world as a whole. (The term is also sometimes used to refer to multiculturalism within an organization. This article does not currently cover that alternative meaning.) There is a general consensus among mainstream anthropologists that humans first emerged in Africa about two million years ago . Since then they 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 people, 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.
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. The General Conference of UNESCO took this position in 2001, asserting in Article 1 of the Universal Declaration on Cultural Diversity that "...cultural diversity is as necessary for humankind as biodiversity is for nature"
This position is rejected by some people, however, 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.
Some individuals, particularly those with strong religious beliefs, maintain that it is in the best interests of individuals and of humanity as a whole that all people adhere to a specific model for society or specific aspects of such a model. For example, evangelical missionary organisations such as the New Tribes Mission actively work to reduce religious diversity by seeking out remote tribal societies to convert them to Christianity; and Islamic groups strategically buy up land in Papua New Guinea.
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. 
The Universal Declaration of UNESCO on Cultural Diversity of 2001 is regarded as a legal instrument recognizing for the first time, cultural diversity as "common heritage of humanity" and considers its safeguarding to be a concrete and ethical imperative inseparable from respect for human dignity.
The Convention for the Safeguarding of the Intangible Cultural Heritage ratified in June 20, 2007 by 78 States said:
"The intangible cultural heritage, transmitted from generation to generation is constantly recreated by communities and groups in response to their environment, their interaction with nature and their history, and gives them a sense of identity and continuity, thus promoting respect for cultural diversity and human creativity. "
Cultural diversity was also promoted by the Montreal Declaration of 2007, and by the European Union. The idea of a global multi-cultural heritage covers several ideas, which are not exclusive. See multiculturalism. In addition to language, diversity can also include religious or traditional practice.
The "defense of cultural diversity" can take several meanings:
Cultural diversity is presented as the antithesis of "cultural uniformity".
Some (including Unesco) fear this hypothesis of a trend towards cultural uniformity. To support this argument they emphasize different aspects:
There are several international organizations 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 European Commission-funded Network of Excellence on "Sustainable Development in a Diverse World" (known as "SUS.DIV") builds upon the UNESCO Declaration to investigate the relationship between cultural diversity and sustainable development.