Vodou resulted from the encounter between Yoruba, Fon and Ewe religions. It crystallized in its present form around the 17th century with the birth and expansion of the Fon kingdom of Abomey. It underpins the Aja-Tado culture, born of several successive migratory waves. The Aja-Tado cultural area ranges from the Ouémé river in the east to the Volta in the west and the so-called Slave Coast in the south. It covers an area 200 to 300 km deep between 0º and 3º longitude, in the heart of what geographers term the Sudanese savanna.
This area is peopled mostly by the following ethnic groups:
The ADJA (AJA) people in the area between Yoto in Togo and the Kouffo in Benin
The EVE (EWE) in the area between the Volta and Yoto
The FON (FON) in the area between the Ouémé and the Kouffo
The GUIN (GÊ) along the so-called Slave Coast
The XWLA and XWÉDA in roughly the same area as the Gê
The GOUN (GUN) in and around the city of Porto-Novo
The AIZO (AYIZO) around lake Nokoué, and around the Allada region
The SAHWÉ in the black lands of Ko in the Bopa region
During the reign of King Agaja (1708 – 1740), Dahomey expanded southwards towards the Atlantic coast, after the conquest of Allada (1724) and Whydah (1727). Its sphere of influence stretched from the borders of the Oyo empire (Nigeria) to those of the Ashanti kingdom (Ghana).
This part of Africa was in contact with European and North African cultures, which explains why Vodou incorporated elements of Christianity, Islam and Judaism.
From the outset, Vodou was a holistic and syncretic religion, reflecting the societies that gave birth to it.