Physostigma venenosum is native to tropical Africa and produces the Calabar bean. The plant grows to heights of 15 meters and produces seed pods containing 2 to 3 chocolate brown beans. The beans contain physostigmine, an alkaloid. If accidentally ingested by humans, these beans produce an effects similar to having been exposed to nerve gas. The toxin disrupts communication between the central nervous system and respiratory organs, resulting in death by asphyxiation.
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The first known inhabitants to settle the area of present day Republic of Congo were the Bambuti people, a group belonging to Pygmy tribes. They were slowly replaced by the Kongo, a branch of the Bantu people. The Kongo began to dominate the region by establishing a loose confederation of tribal kingdoms along the mouth of the Congo River. At the height of power, this Kongolese kingdom had a population of 4 million inhabitants and covered an area of 300,000 square kilometers.
