In this week's Science, two independent research groups report data showing that RNAi interference is used by mammals to fend off viral pathogens, as well as to control levels of endogenous genes. In one study, investigators looked at undifferentiated mouse embryonic stem cells, which lack an interferon immune response system, and found an accumulation of RNAi molecules after viral challenge. In the other report, scientists show that suckling mice also use an RNAi response to fight off viral infection.
A separate pair of papers appearing in Science examine population changes in Central Europe from the Mesolithic period to the Neolithic period. One study from the Genographic Project and others finds hints in ancient DNA from a number of archeological sites that there was a time of genetic continuity for some 2,500 years the onset of farming. After that, a series of changes in genetic composition occurred. The other study, from researchers at Johannes Gutenberg University and elsewhere, found using a combination of DNA and isotope analysis that hunter-gatherers and farmers lived side by side in Central Europe for some 2,000 years.