An Example of Exhaustion of Genetic Variation
Any group, even the most primitive, is genetically highly varied. Customs preventing inbreeding help keep even the smallest human population rich in genetic variations. The only example I know of a human population in which genetic variety was apparently partially exhausted is that of the tribes of the Indian-controlled Andaman Islands, near Burma.
There were at least four Andaman tribes, who spoke different, but related languages. In the nineteenth century, these tribes were still made up of a reasonable number of people, and at least one still numbered five or six thousand. Contact with whites, and the British in particular, has virtually destroyed them. Illness, alcohol, and the will of the colonials all played their part; the British governor of the time mentions in his diary that he received instructions to destroy them with alcohol and opium. He succeeded completely with one group. The others reacted violently.
Ancient travelers give differing accounts of the Andaman tribes' behavior toward visitors. Marco Polo said they were fearsome, but, because he also says they had dogs' heads, I doubt he had been to the islands himself. Giovanni dal Pian del Carpine, another Venetian who preceded him, states that they were most well mannered. The truth may be that the different tribes had varying reactions to outsiders. In the mid-1800s, when a British ship visited Little Andaman Island and sent a launch ashore, the native Onge captured some of the sailors, cut off their arms and legs, and then burned the still-living trunks on the beach before the eyes of those who had managed to escape back to the ship. The British reaped terrible revenge a year later. A group of soldiers went ashore and waited until the natives came onto the beach; they then opened fire and killed about seventy before returning to their vessel.
There was no further contact between the Onge and Westerners until the twentieth century. In 1951 an Italian anthropologist, Lidio Cipriani, went to the island for two years and conducted some excellent research. He managed to gain the people's trust and became the first to provide accurate information. He explained, for example, why the Onge mutilated the British sailors and then burned the trunks. According to their religion, if they had not done so the spirits of the dead could have returned to haunt them.
These people were extremely primitive. They had even lost the ability to create fire. They knew how to protect it, but could not produce it. The pygmies, however, know how to make fire, although they find it easier to keep it lit. The women carry embers with them through the forest.
The numbers of Andaman natives had already declined considerably, even without the British. Today the Little Andaman Onge number no more than ninety-eight or ninety-nine people, too few to avoid close inbreeding. The result is that most couples have no children, or have, at most, only one or two. They are careful to ensure the tribe's survival, so if a girl has no children from a first marriage she is taken and married to another, and then another if necessary.
Another group of Andaman natives, on tiny Sentinel Island, indicated in January 1991 that they were willing to make contact with the Indian government for the first time. I suspect that these are the last native people never to have had contact with the rest of the world.