COVER STORY: Not just for spiders, silk threads could be used to make bulletproof vests and scaffolding for growing cartilage, among other materials.

On the cover: From a standing start, bushbabies can easily outjump humans. Photo: John Downer Productions

Photos: Getty/Siri Stafford; iStockphoto/luismmolina On the cover: Inserting foreign genes that boost strength and endurance into DNA may appeal to athletes -- leading anti-doping officials to search for ways to test competitors for signs of gene doping. Full story.