二足歩行の起源した場所の植生
巻島美幸(滋賀県立総合保健専門学校)



The aim of this presentation is, following the two preceding two studies in this symposium, to discuss the modern vegetation and its capacity as a proxy for the human ancestors. The first study of sedimentology and the second paleontology both showed of some degree a mixed vegetation of closed, wooded landscape and relatively open, grassy one. Nachola area, the area of this study, northern Kenya is reported the average annual rainfall just over 500mm. It has a mixed vegetation of "savanna" like open land, plains dominated by dwarf shrub, with some seasonal rivers fringed by riparian forests composed partly of a species of fig genus, Ficus sycomorus. The majority of the fruit produced here is of this species. For frugivorous mammals, this species production is worth depending on, and carring capacity of this riverine forest is estimated roughly from the fig amount. The production is assumed by counting the number of fig trees and the numbers of figs on some trees. Field counting was just once in a year, then underestimation for annual product could be involved. To the contrary, interspecific competition and other constraints could bring overestimation when considered. From the energy requirement, the fig as the amount of production can sustain a small group of medium sized mammals such as early hominid, in an arid riverine forest. This infer that larger riparian forest, which might have existed around the period, is a highly probable vegetation of harbouring the population of human ancestor.





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