PhD defence

Do not fear the supernatural! The relevance of ritual plant use for traditional culture, nature conservation, and human health in western Africa

PhD candidate ms. DK (Diana) Quiroz Villarreal
Promotor prof.dr. MSM (Marc) Sosef
Co-promotor dr. TR van Andel
Organisation Wageningen University, Biosystematics

Fri 20 March 2015 11:00 to 12:30

Venue Aula, gebouwnummer 362
Generaal Foulkesweg 1
6703 BG Wageningen


African traditional religions are based on ancestor worship, magic, medicine, and spirit possession. Although these beliefs are strongly connected to the natural world, their associated plants were only scarcely studied. Mexican ethnobotanist Diana Quiroz documented over 600 ritual plants used in Benin (West Africa) and Gabon (Central Africa). She interviewed Voodoo and Bwiti followers, surveyed fetish markets, and accompanied traditional healers to their sacred forests and shrines. Her research shows that plants play a central role in traditional beliefs. Rituals are a way of transmitting ecological, historical, and medicinal knowledge. Magic plants are of considerable economic value for millions of Africans involved in their collection, processing, and trade. Species getting scarce are protected by taboos, sacrifices, and cultivation. Although previously thought to be just placebos, Quiroz shows that 75% of the plant species are orally ingested or applied in baths or skin incisions, suggesting potential pharmacological effects on their users.


  1. Advocating a limited pharmacological relevance of African ritual practices and plant use is evidence of the ignorance of the sceptic, rather than a demonstration of “the gullibility of the credulous”. (this thesis)
  2. In studies that address the use of natural resources in the context of religious traditions, it is relevant to acknowledge people’s behaviour in the name of supernatural entities, rather than to define the realm of religion. (this thesis) 
  3. Tithes and h-indexes are misleading measures of the patronage of devotees and the productivity of scientists as they place churches and universities closer than their defendants care to admit, and further away from the truth that both religion and science claim to pursue. 
  4. A “University of Life Sciences” that rids itself from its arboretum, herbarium and entomological collections is like a person who has her eyeballs extirpated in order to save money on reading glasses. 
  5. A solution to the world’s current social, environmental, and economic crisis will not come from educating the uneducated, but from edifying the educated. 
  6. Just as plants, humans will not survive without their roots. 
  7. Together, a peaceful mind and a humble heart are a workshop of creativity.