Although Francis Galton was the first to use twins for comparative genetic studies in a scientific way, there had been considerable interest and speculation about twinning from very early times. This has been referred to in numerous publications in the past, and indeed, Professor Gedda, Founding President of our Society, has written extensively on this [9]. The earlier writings referred almost entirely to the twins themselves, and there seemed to have been little attention paid to the mothers, except that they were either considered to have had intercourse with two men, or indeed, with a deity. Galton also referred in his publication of 1876 [8] to the largeness of the families into which twins are born, but a graduate of Aberdeen University, James Matthews Duncan, had pointed out some of the characteristics of mothers having twins ten years earlier. In 1865 he published his paper “On the Comparative Frequency of Twin-Bearing in Different Pregnancies” [7] and in this he showed that mothers of twins tended to be of higher parity and older. This very accurate observation has since been confirmed, but is was not clear whether age and parity were separate factors until Anderson, again working in Aberdeen, showed in 1956 that the twinning incidence increased up to a peak at age 35 and thereafter fell [1].