Whenever I saw a patient suffering from porphyria variegata, I interviewed all the relatives I could find, examined them for porphyria and drew up a family tree. In this way I was able to find out from which side of the family porphyria had been inherited. All the families I studied came from Afrikaner, or Boer, stock. It was possible to trace the ancestors from the family bibles and from the baptismal records of the Dutch Reformed Church. The way the Afrikaners named their children was also a great help; the first son was always given the names of the father's father, the second son those of the mother's father, and the third son the father's own names. The first daughter was given the names of the mother's mother, the second those of the father's mother, and the third the mother's names. This meant that the first-born uncle would have the same names as the great-grandfather. I was able to trace the families on the affected side back about 150 years, to the early part of the nineteenth century. After a great deal of research, I traced 32 family groups to their ancestors back about five or six generations.

Tracing the porphyric families to earlier than the nineteenth century was made easier by research carried out by Christoffel Coetzee de Villiers, the editor of the Het Volksblad newspaper, in the 1870s and 1880s. He found the names of the ancestors of his own family and those of most of the old Boer families from their baptismal records back to their ancestors who had come from Europe, many in the latter half of the seventeenth century. When he died in 1884, de Villiers's register of the old Cape families was published in three volumes. Dr J. Hoge studied the families of the early German settlers, while C.G. Botha made a careful examination of French Huguenot refugee families who had come to the Cape about 1688.