Over the past decade geneticists have proved that all people alive today are descendants of a relatively small number of individuals who walked out of Africa some 60,000 years ago and carried the human spirit and imagination to every corner of the habitable world. Our shared heritage implies that all cultures share essentially the same potential, drawing on similar reserves of raw genius. Whether they exercise this intellectual capacity to produce stunning works of technological innovation (as has been the great achievement of the West) or to maintain an incredibly elaborate network of kin relationships (a primary concern, for example, of the Aborigines of Australia) is simply a matter of choice and orientation, adaptive benefits and cultural priorities. Each of the planet’s cultures is a unique answer to the question of what it means to be human. And together they make up our repertoire for dealing with the challenges that will confront us as a species in the millennia to come.

But these global voices are being silenced at a frightening rate. The key indicator of this decline in cultural diversity is language loss. A language, of course, is not merely a set of grammatical rules or a vocabulary. It is the vehicle by which the soul of each particular culture comes into the material world. Each one is an old-growth forest of the mind. Linguists agree, however, that 50 percent of the world’s 7,000 languages are endangered. Every fortnight an elder dies and carries with him or her into the grave the last syllables of an ancient tongue. Within a generation or two, then, we may be witnessing the loss of fully half of humanity’s social, cultural and intellectual legacy. This is the hidden backdrop of our age.

People often ask why it matters if these exotic cultures and their belief systems and rituals disappear. What does a family in New York care if some distant tribe in Africa is extinguished? In truth it probably matters little, no more than the loss of New York would directly affect a tribe in Africa. I would argue that the loss of either way of life does matter to humanity as a whole.

Consider the achievements of the Polynesians. Ten centuries before Christ—at a time when European sailors, incapable of measuring longitude and fearful of the open ocean, hugged the shores of continents—the Polynesians set sail across the Pacific, a diaspora that would eventually bring them to every island from Hawaii to Rapa Nui, the Marquesas to New Zealand. They had no written word. They only knew where they were by remembering how they had got there. Over the length of a long voyage the navigator had to remember every shift of wind, every change of current and speed, every impression from sea, sky and cloud. Even today Polynesian sailors, with whom I have voyaged, readily name 250 stars in the night sky. Their navigators can sense the presence of distant atolls of islands beyond the visible horizon by watching the reverberation of waves across the hull of their vessels, knowing that every island group had its own reflective pattern that can be read with the ease with which a forensic scientist reads a fingerprint. In the darkness they can discern five distinct ocean swells, distinguishing those caused by local weather disturbances from the deep currents that pulsate across the Pacific and can be followed as readily as a terrestrial explorer would follow a river to the sea.

There are many such examples of ancient wisdom. Among the Barasana people of the northwest Amazon in Colombia, for whom all the elements of the natural world are inextricably linked, complex mythologies about the land and its plants and animals have given rise to highly effective land-management practices that serve as a model for how humans can live in the Amazon basin without destroying its forests. The Buddhists of Tibet spend their lives preparing for a moment that we spend most of our lives pretending does not exist: death. Surely their science of the mind—informed by 2,500 years of empirical observation—has something meaningful to contribute to the human patrimony.

This is not to say that cultures should be forced to remain static, that they cannot maintain their identity while changing some of their ways. The Haida did not stop being Native American when they gave up the dugout canoe for the motorboat any more than ranchers in Montana ceased being Americans when they put aside the horse and buggy in favor of the automobile. It is not change or technology that threatens culture; it is domination.

The ultimate tragedy is not that archaic societies are disappearing but rather that avertible forces are driving vibrant peoples and languages out of existence. These external threats take many forms. They may be industrial, as in the case of the egregious forestry practices that have destroyed the subsistence base of the nomadic Penan in the rain forests of Borneo, or the toxic effluents of the petrochemical industry that have compromised the once fertile soils that the Ogoni people of the Niger Delta farmed. Epidemic disease is another menace to culture—to wit, the ­Yanomamï of the Amazon have suffered dreadful mortality as a result of exotic pathogens brought in­to their lives by the gold miners who have invaded their lands. Or the threat may be ideology, as in the domination of ­Tibetan Buddhists by the Communist Chinese.

That cultures do not always fade away but rather may be casualties of other societies’ priorities is actually an optimistic observation, because it suggests that if humans are the agents of cultural decline, we can foster cultural survival. Following the Colombian government’s 1991 decision to grant land rights to the Indians of the northwest Amazon, for example, the Barasana are now flourishing. Our goal should not be to freeze people in time. Instead we must find ways to ensure that in a pluralistic, interconnected world all peoples may benefit from modernity without that engagement demanding the sacrifice of their ethnicity.