WASHINGTON - Proving prehistoric man's ingenuity and ability to withstand and inflict excruciating pain, researchers have found that dental drilling dates back 9,000 years. Primitive dentists drilled nearly perfect holes into live but undoubtedly unhappy patients between 5500 B.C. and 7000 B.C., an article in Thursday's journal Nature reports. Researchers carbon-dated at least nine skulls with 11 drill holes found in a Pakistan graveyard.That means dentistry is at least 4,000 years older than first thought — and far older than the useful invention of anesthesia.This was no mere tooth tinkering. The drilled teeth found in the graveyard were hard-to-reach molars....