This study focuses on the ancient past of coastal Guinea's Rio Nunez region, a coastal rice-growing region virtually unexplored by studies of West African rice and rice farmers. It argues that coastal cultivators have adapted mangrove rice-farming systems in situ for approximately the past 1,000 years, a historical period pre-dating the European travelers' accounts on which the current literature heavily relies. Rather than diffusing from the interior, these specialized farming systems grew organically out of land-use systems. Using the comparative method of historical linguistics and cultural vocabulary, the study establishes different stages in coastal farmers' experimentation, adaptation and specialization in the coastal environment and approximates historical dates when the different stages occurred. And with botanical and biological studies of mangrove vegetation, the study distinguishes between the softer, spongy roots of white mangroves and hard, twisted roots of red mangroves. The interdisciplinary evidence reveals that knowledge of white mangroves was an early formative stage in cultivators' fabrication of coastal land-use systems. Lastly, from an examination of loanwords, the study discusses the important contributions made by Mande groups, who speak the Susu language in the Rio Nunez region, in intensifying mangrove rice-farming systems indigenous to the coast and extending them from zones of white to those of red mangroves. The interdisciplinary methods and sources enable the study to capture localized experimentation and innovation as continuous processes, thereby breaking with the current literature's emphasis on diffusion from the interior to the coast.