ocr: Identical yet individual, 77-year-old Kirsten, at left, and Grethe Hermansen, respond as: oner during a coordination: test in their Copenhagen: home. part ofa Danishi study, of aging int twins. "We have found that about a quarter ptthe variation in howi long we live can be explained by genetic factors, says epidemiologistKaare Christensen, who: directs the research.
