In a wide survey of twin births which was made in Sardinia, covering the years from 1902 to 1954, it was found that there was an incidence of 9.2 multiple births out of a thousand, which may be considered the lowest for any of the regions of Italy. The survey comprised not only the three provinces, but individual zones which are distinguished by historical and geographical differences.
In each of these areas a different trend appeared in what might be termed the twin phenomenon due, obviously, to the characteristic hereditary traits of the population, the degree of isolation and the endogamy which has usually been praticed over a long period.
In a commune of Campidano di Cagliari, Serramanna, research was made to ascertain what part heredity played in twin births, with positive results.
Furthermore, MZ and DZ twins were studied for the resemblance or non-resemblance in certain characteristics such as the form and colour of the hair, the skin colour, the m.c.c, the colour of the iris.
This survey of twins has shown itself to be a truly suitable method for the study of the patrimony of heredity of the Sardinians who are a Mediterranean population which are anthropologically and ethnically a distinct group on their own.