A genomic analysis shows that precursor cells pb that form index finger in five-fingered vertebrates can form the "thumb " (in orange) or first digit in three-digit bird wing Evolution adds and subtracts, and nowhere is this math more evident than in vertebrates, which are programmed to have five digits on each limb. But many species do not. Snakes, of course, have no digits, and birds have three.

Professor Nigel Minton works at the University of Nottingham. A bacterial strain that specifically targets tumours could soon be used as a vehicle to deliver drugs in frontline cancer therapy. The strain is expected to be tested in cancer patients in 2013 says a scientist at the Society for General Microbiology's Autumn Conference at the University of York.