GENETIC ARCHAEOLOGY: A matchbox-size chunk of dental tartar cut from this 1,000-year-old jaw inspired the study of differences in the oral bacterial communities of early and modern humans.COURTESY OF ALAN COOPERThe idea took root with the offer of an unusual gift—a hefty chunk of ancient dental tartar. In 1996, while a postdoc at the University of Oxford, biological anthropologist Alan Cooper visited archaeologist Keith Dobney at York University. They had already discussed several ideas, including how they might use ancient tartar—otherwise known as dental calculus—when Dobney pulled from his desk drawer a matchbox-size brownish-grey block of the stuff, taken from a 1,000-year-old skeleton. “I was amazed,” recalls Cooper.
Dobney, now at the University of Aberdeen in Scotland, had been using scanning electron microscopy to examine the calculus for traces of food when he noticed an abundance of fossilized bacteria. He suggested it might also be a source of extractable bacterial DNA—a prize that could offer a glimpse into the evolution of the human microbiota and of human disease. Cooper was keen to try, but knew that even the most sterile lab consumables—from plasticware to enzymes—contained traces of bacterial DNA, so he was never confident that his early results were free from contamination.
Almost 2 decades later, armed with ultrasterile consumables and an ultraclean lab at the University of Adelaide’s Australian Centre for Ancient DNA—where he is now director—Cooper and his colleagues have used ...
