Plant types and seasonality of wild-plant foods, Tanzania to Southwestern Africa: Resources for models of the natural environment

Abstract

Pursuant to understanding the ecological adaptations of the African hominids, we have analysed some of the characteristics of 419 wild plant species exploited for food by humans in a broad portion of the African summer-rain climatic region running from Tanzania to southwestern Africa. With regard to general growth form: trees, arborescents (other woody forms that can mature as trees), and forbs provide the majority of edible species. Although the grasses are diverse and abundant, most appear not to provide food items for humans. Woody rosette forms (e.g. palms and cycads) and truc shrubs (as opposed to arborescents) are both species-poor. The woody vines and lianas appear to provide even fewer edible species. Stem succulents, parasites, and ferns provide almost no edible species. When scasonality and growth form are both taken into consideration, deciduous trees, perennial forbs, and mushrooms are the most species rich “edible” plant types. Deciduous trees primarily provide edible fruit/seed/pods, particularly during the rainy season, leaves in the rainy season and some underground parts on a more or less year-round basis. Perennial forbs provide flowers, fruit/seed/pods, or leaves in the rainy season, but most (78%) of the edible species also provide underground parts on a more or less year-round basis. The general pattern of species providing edible above-ground parts in the rainy season is reinforced by the mushrooms, evergreen/semi-evergreen trees, and arborescents, as well as the speciespoor plant types. The overall potential dictary pattern is that of a pronounced seasonal change in the quality of plant foods, from a variety of types of food items provided by several different types of plants during the rainy season to mainly fruit/seed/pods and/or underground parts in the dry season. This implies a predictable qualitative as well as quantitative scasonal shift in the wild-plant-food diet of prehistoric humans wherever the tropical summerrain climate imposed itself or remained in effect.