Original Research

Africa and Precambrian biological evolution

A. H. Knoll
Bothalia | Vol 14, No 3/4 | a1177 | DOI: https://doi.org/10.4102/abc.v14i3/4.1177 | © 1983 A. H. Knoll | This work is licensed under CC Attribution 4.0
Submitted: 31 October 1983 | Published: 06 November 1983

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Abstract

African sedimentary rocks and their contained fossils have played a fundamental role in the unravelling of Precambrian biological history. Various lines of evidence including stromatolites, filamentous and coccoidal microfossils, stable isotope ratios, organic carbon distribution, and oxide facies iron formation suggest that a complex prokaryotic ecosystem fueled by photosynthesis, and perhaps including aerobic photoautotrophs, existed as early as 3 500 m.y. ago. The primary sources of data on early Archean life are rock sequences in southern Africa and Australia. The diversity of later Archean (ca. 2 700 m.y.) communities is attested to by abundant and varied stromatolites found in Zimbabwe.

The extensive growth and consolidation of continents that heralded the Proterozoic Eon had profound effects on the earth’s biota. Primary productivity must have increased substantially, resulting in the establishment of an 02-rich atmosphere, and, subsequently, the radiation of aerobic respirers. Southern African sequences provide critical evidence bearing on this crust/atmosphere/biota interaction; however, the best known microfossils of this age come from North America.

Upper Proterozoic sedimentary rocks abound in Africa. Stromatolites from northwestern Africa have been well studied; however, microfossil occurrences remain but sketchily described. Contemporaneous sequences from Scandinavia and Australia document the initial radiation of eukaryotes in the planktonic realm, as well as a terminal Precambrian episode of extinction among plankters. Early heterotrophic protists are known from several continents. The Nama Group of South West Africa/Namibia contains important evidence of early invertebrates.

In general, Precambrian evolution can be viewed as a series of increasingly elevated biological plateaus connected by steps marking relatively short periods of evolutionary innovation and radiation. With each step, communities have increased in complexity, but prokaryote mediated element cycles established early in biological history remain at the core of functioning ecosystems.


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Crossref Citations

1. Phanerozoic evolution of plants on the African plate
P.M. Burgoyne, A.E. van Wyk, J.M. Anderson, B.D. Schrire
Journal of African Earth Sciences  vol: 43  issue: 1-3  first page: 13  year: 2005  
doi: 10.1016/j.jafrearsci.2005.07.015