There are an estimated 15,000 cultures remaining on earth, many doomed or significantly threatened by erosion of cultural integrity, loss of habitat and environmental quality, and the ravages of disease and socio-economic infections. With them goes expertise and wisdom of elders, healers, midwives, farmers, fishermen and hunters, mostly transmissible only by oral tradition to respectful successors.
Most of the 15,000 cultures are represented by a single population of several hundred persons or less, dependent on pockets of land which are increasingly under threat from other uses or environmental destruction. Since 1900, 90 of Brazil's 270 Indian tribes have completely disappeared, while scores more have lost their lands and abandoned their ways. More than two-thirds of the remaining tribes have populations of fewer than 1,000. The pygmies, who live in the equatorial forests of Uganda and Zaire, are on the verge of extinction; possibly 300 are left and the numbers are dwindling.