L. Adolphe Quetelet (1796-1874), Flemish astronomer, mathematician, statistician and sociologist. Lambert Adolphe Jacques Quetelet was influential in many areas of science and mathematics. He founded and directed the Brussels Observatory in 1832 as well as writing notable papers on social statistics. In 1885, he was the first to demonstrate that the 'average man' was the central value (the mean) of measured variables (such as height or weight) that followed a normal distribution (a range of values that produce a bell-shaped curve on a graph). Quetelet also proposed a simple measure for classifying people's weight against the ideal weight for their height, which is known today as the body mass index (BMI).