A team of researchers from Duke University studied a nearly 1000 people born within a year of each other and found a huge gulf in the speed at which their bodies aged. The subjects were from the same town in New Zealand and were all born in 1972-73. The scientists looked at 18 different ageing-related traits when the group turned 26, 32 and 38 years old. They measured everything from kidney and liver function to cardiovascular fitness and the condition of their gums.