Jointed limbs in arthropods are a key innovation that facilitated the evolution of the world's most species-rich animal group. Their ancestors may lie among a group of extinct animals called lobopodians, which looked rather like worms with legs. A newly discovered 520-million-year-old fossil lobopodian from China may be the closest known fossil relative of modern arthropods. A thin worm-like animal, Diania cactiformis is named to reflect its 'walking cactus' appearance. The possession of what seem to be the beginnings of robust, jointed and spiny legs suggest that this bizarre animal might be very close to the origins of the arthropods. Illustration: Mingguang Chi

On the cover, the southern Bavarian village of Eschenlohe in August 2005, partially evacuated after the river Loisach flooded following heavy rain. A significant effect of anthropogenic activities has already been detected in observed trends in temperature and mean precipitation. But to date, no study has formally identified a human fingerprint on extreme precipitation, and it has proved difficult to assess the human impact on specific types of weather events. Two groups now present evidence that anthropogenic greenhouse gases have significantly increased the probability of heavy precipitation and local flood risk. Min et al. compare observations and simulations of rainfall between 1951 and 1999 in North America, Europe and northern Asia. They find a statistically significant effect of increased greenhouse gases on the incidence of extreme precipitation events over much of the Northern Hemisphere land area. Pall et al. use publicly contributed climate simulations to show that increased greenhouse-gas emissions substantially increased the risk of flood occurrence during the extensive flooding in England and Wales in autumn 2000. In News & Views, Richard Allan discusses the technical challenges associated with predicting regional changes in the water cycle. Cover credit: Reuters.

It is 10 years to the month since the publication of a draft sequence of the human genome by the Human Genome Project. To mark the anniversary, this issue of Nature includes three major papers on human genomics. The light bulb theme on the cover relates to one of them, in which Eric Green, Mark Guyer and others from the US National Human Genome Research Institute provide a vision for the future of genomic medicine (page 204). Eric Lander, present at the birth of the Human Genome Project, looks back at what has been achieved in genomics and speculates on future prospects (page 187). And Elaine Mardis (page 198) discusses the DNA sequencing technologies that have catalysed rapid genomic advances during the past ten years. Picture credit: Darryl Leja & Jay Latman (NHGRI, NIH).

NASA’s Kepler mission, a space observatory designed to detect and study extrasolar planets that transit across the disk of their host star, has hit the jackpot with the discovery of a six-planet system orbiting a Sun-like star now named Kepler-11. Five of the planets have orbital periods of between 10 and 47 days, and these are among the smallest for which size and mass have both been measured. The sixth and outermost transiting planet has been less well characterized thus far. Only one other star has more than one confirmed transiting planet (Kepler-9, which has three). This newly discovered system resembles our own Solar System in being close to coplanar, but Kepler-11's planets orbit much closer to their star. Kepler is due to continue to return data on Kepler-11 and its planets for some time yet, and it should provide many valuable constraints on models of the formation and evolution of solar systems in general. The cover illustration shows an artistic impression of the triple transit observed on 26 August 2010. Picture credit: NASA/Ames/JPL-Caltech/T. Pyle