Renner was born in Sierra Leone to an affluent Creole family.
[1] Renner stated that there was an increasing number of cases of cancer of different organs, especially the breast among the descendants of the liberated Africans or Creoles of Sierra Leone, while cancer was rare among the aborigines of West Africa.
[2][3] According to Renner, cancer was rarely found among the hundreds of female aborigines who were treated every year at the Colonial Hospital, nor was it reported by medical officers in large towns at dispensaries where natives had been encouraged to attend for treatment.
[2] He concluded that cancer was rare among the aborigines because of "their primitive mode of living", such as eating grains and vegetables, while the Creoles had adopted the habits of the European civilization, such as eating large quantities of butcher's meat.
[4] John Randle disagreed with Renner's theory and stated that cancer was seen less frequently among aborigines in hospital because natives were superstitious and would instead have preferred to visit local country doctors.