Onset of Asian desertification by 22 Myr ago inferred from loess deposits in China

The initial desertification in the Asian interior is thought to be one of the most prominent climate changes in the Northern Hemisphere during the Cenozoic era. But the dating of this transition is uncertain, partly because desert sediments are usually scattered, discontinuous and difficult to date. Here we report nearly continuous aeolian deposits covering the interval from 22 to 6.2 million years ago, on the basis of palaeomagnetic measurements and fossil evidence. A total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils. This new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of Asia by the early Miocene epoch, at least 14 million years earlier than previously thought. Regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in Asia.

Earliest presence of humans in northeast Asia

The timing of the earliest habitation and oldest stone technologies in different regions of the world remains a contentious topic in the study of human evolution. Here we contribute to this debate with detailed magnetostratigraphic results on two exposed parallel sections of lacustrine sediments at Xiaochangliang in the Nihewan Basin, north China; these results place stringent controls on the age of Palaeolithic stone artifacts that were originally reported over two decades ago. Our palaeomagnetic findings indicate that the artifact layer resides in a reverse polarity magnetozone bounded by the Olduvai and Jaramillo subchrons. Coupled with an estimated rate of sedimentation, these findings constrain the layer's age to roughly 1.36 million years ago. This result represents the age of the oldest known stone assemblage comprising recognizable types of Palaeolithic tool in east Asia, and the earliest definite occupation in this region as far north as 40 degrees N.

Changes in oral health knowledge and behaviour 1987-95 among inhabitants of Wuhan City, PR China

The purpose of this study was to evaluate the changes of oral health knowledge and behaviour among Wuhan citizens after six years of 'Love Teeth Day' campaigns. Representative samples of citizens aged 10-62 years were identified and interviewed in 1987 (n = 1180) and in 1995 (n = 1014). Data on oral health knowledge and practises were collected by structured questionnaires in both surveys and high response rates were obtained (87-94 per cent). In general, improvements in oral health knowledge and toothbrushing behaviour were observed in 1995 as compared with 1987. The younger age group (10-19-year-olds) showed significantly higher improvements of positive answers to knowledge items and toothbrushing behaviour. The findings also indicated that less than half of the interviewees were aware of the anti-caries effect of fluoride and about 30 per cent of the participants brushed their teeth performing the recommended method (vertical). In China, community based oral health education programmes should be implemented to further improve regular self-care practises, especially in relation to the adult population.