What is the secret to a long life? Three Brazilian sisters with a combined age of 316, who were named by Guinness this month as the oldest living trio of siblings in the world, may help researchers find out.The DNA Longevo Project, a study led by scientist Mayana Zatz from the University of Sao Paulo, aims to investigate the biological factors behind ageing.Findings from the three sisters’ case could help scientists better understand why some people remain physically and cognitively...