Tooth gives up oldest human DNA

Scientists have recovered DNA from a Neanderthal that lived 100,000 years ago – the oldest human-type DNA so far. It was extracted from the tooth of a Neanderthal child found in the Scladina cave in the Meuse Basin, Belgium. The study, reported in Current Biology, suggests our distant cousins were more genetically diverse than once thought. Their diversity had declined, perhaps because of climate change or disease, by the time early humans arrived in Europe about 35,000 years ago. French and Belgian researchers isolated the genetic material from mitochondria. These are “power pack” structures in cells which contain their own DNA.

The scientists decoded the sequence of 123 DNA “letters” (base-pairs, or bp) and compared it with other known Neanderthal DNA sequences from specimens dated between 29,000 and 42,000 years old. “The Scladina sequence has revealed that the genetic diversity of Neanderthals has been underestimated,” a team led by Dr Catherine Hanni of Ecole Normale Superieur in Lyon, France, wrote in the journal Current Biology. “Thus, more Neanderthal sequences than the six presently available and longer than 100 bp are needed to fully understand the extent of the past diversity of Neanderthals.”

The findings suggest that genetic diversity was greater in earlier Neanderthal history than in later times, when humans started to arrive in Europe. The DNA came from the molar of a 10-12 year-old child. Such changes are thought to reflect fluctuations in the population, caused by disease or environmental change, as well as random genetic mutations over time. “Diversity tells us about how old a population is and its demographic history,” said Dr Robert Foley, an expert in human evolution at the University of Cambridge, UK.

Neanderthals lived between 230,000 and 28,000 years ago in Europe, Central Asia and the Middle East. They were skilled hunters and well adapted to living during the ice ages; but they started to die out after modern humans (Cro-Magnons) appeared on the scene in Europe. The reason for their sudden demise is unknown, but various theories have been proposed, including biological, environmental and cultural factors. The DNA studies conducted so far suggest little, if any, interbreeding between Neanderthals and modern humans took place.

BBC News
June 20, 2006

Original web page at BBC News


9,000-year-old drilled teeth are work of stone age dentists

Researchers excavating a Stone Age graveyard found a total of 11 teeth that had been drilled, including one that had apparently undergone a complex procedure to hollow out a cavity deep inside the tooth. The discovery suggests a high level of technological sophistication, though the procedure, which involved drills tipped with shards of flint, could hardly have been a painless affair. “The finding provides clear and compelling evidence that earlier people had knowledge of manipulation of dental hard tissues in living people,” said Clark Spencer Larsen, an anthropologist at Ohio State University in Columbus, who was not part of the excavation.

“We think the drilling had medical reasons,” said Roberto Macchiarelli, a paleoanthropologist at the Université de Poitiers and lead author of the study. “While some teeth had been drilled more than once, four showed signs of decay … suggesting a possible therapeutic intervention.” The procedure could not have had an aesthetic purpose, since its results were not easily visible, he added. But the real motive is still uncertain. “The reason is difficult to ascertain,” said Jeffrey Schwartz, an anthropologist at the University of Pittsburgh in Pennsylvania.

National Geographic
April 25, 2006

Original web page at National Geographic


Amoxicillin use during infancy may be linked to tooth enamel defects

Use of the antibiotic amoxicillin during infancy appears to be linked to tooth enamel defects in permanent teeth, according to a study in the October issue of Archives of Pediatrics and Adolescent Medicine, one of the JAMA/Archives journals. Dental fluorosis, a result of exposure to excessive fluoride during enamel formation, is one of the most common developmental enamel defects, according to background information in the article. The clinical signs range from barely noticeable white flecks, to pits and brown stains. Amoxicillin is one of the most common antibiotics used among pediatric patients, mainly for treatment of otitis media–infection and inflammation of the middle ear. There has been some evidence that amoxicillin use could be associated with dental enamel defects, and, the authors suggest, even a small effect on dental enamel could have a significant effect on the public’s dental health because of the widespread use of amoxicillin.

The researchers analyzed data from the Iowa Fluoride Study, a prospective study investigating fluoride exposures, biological and behavioral factors, and children’s dental health. They followed 579 participants from birth to 32 months, using questionnaires every three to four months to gather information on fluoride intake and amoxicillin use. “The results show that amoxicillin use during early infancy seems to be linked to dental fluorosis on both permanent first molars and maxillary central incisors,” the authors report. “Duration of amoxicillin use was related to the number of early-erupting permanent teeth with fluorosis.” By the age of one year, three-quarters of the subjects had used amoxicillin. By 32 months, 91 percent of participants had used amoxicillin. “Overall, 24 percent had fluorosis on both maxillary central incisors,” the authors write.

Amoxicillin use from three to six months doubled the risk of dental fluorosis. “The significantly elevated risk for dental fluorosis associated with amoxicillin use during early infancy was found at all levels of statistical analyses, even after controlling for other potential risk factors, such as fluoride intake, otitis media infections, and breastfeeding,” the authors report. The authors emphasize that additional laboratory and clinical studies–including controlled animal studies with specified amoxicillin dosages, chemical analysis and histological examination of affected teeth, and additional well-designed epidemiological studies–are needed to confirm the results. “The findings suggest that amoxicillin use in infancy could carry some heretofore undocumented risk to the developing teeth,” they conclude. “While the results of this one study do not warrant recommendations to cease use of amoxicillin early in life, they do further highlight the need to use antibiotics judiciously, particularly during infancy.”

Source: Arch Pediatr Adolesc Med. 2005;159:943-948

Science Daily
November 8, 2005

Original web page at Science Daily