Swartkrans Cave

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Swartkrans is a fossil hominin-bearinig cave situated approximately 1km to the west-northwest of the well known fossil site of Sterkfontein in the Cradle of Humankind World Heritage Site.

History of Investigations

The earliest palaeontological work at Swartkrans dates to 1948 when Robert Broom began collecting fossils at the request of the University of California African Expedition.[1] Broom worked at the site until his death in 1951, and he, and later John Robinson, recovered a large amount of hominin material. This material included the first recorded occurrence of more than one hominin species in a single deposit: Paranthropus robustus alongside a type of early Homo [1]. Robinson continued his work at Swartkrans until 1953, when the site was abandoned [2]. In 1965, C.K. Brain of the Transvaal Museum resumed work at the site, work that continued for the next 21 years[2]. Brain’s excavations involved sampling mining displaced breccia blocks, as well as the first in situ excavations at the site[3]. . The meticulous nature of the provenience data that he recorded (a level far beyond what was generally accepted as the norm at the time) allowed a workable Geographical Information System (GIS) based 3-D map of in situ deposits to be reconstructed [4]. The faunal assemblage that Brain was able to extract from this site was instrumental in his re-interpretation of the way bones accumulate in the fossil caves, detailed in his (1981) book, titled The Hunters or the Hunted? [3]. Other notable discoveries at Swartkrans included evidence of the earliest controlled use of fire [5], as well as a number of bone tools that are thought to be termite mound digging implements [6].

Geology of the site

Brain (1958) provided the first comprehensive geological study and developed the first model for the stratigraphy of the site[7]. Work continued at Swartkrans for the following two decades and in the mid 1970s Butzer advanced on Brain’s earlier work and formally defined the Swartkrans Formation, with two component members[3]. It was not, however, until 1979, when Brain began in situ excavations of the sedimentary strata of Members 1, 2 and 3, that meaningful geological data was generated[4]. His efforts provided a number of insights into the complexity and nature of the fill, and led to the development of a five-member stratigraphy for the site, with each member separated from its older counterpart by an erosional discontinuity (an period of time between the deposition events) [8].

Geological Members

There have been five geological “Members” identified at Swartkrans. Member 1 represents the early stage of fill. Member 2 is believed to be separated from Member 1 by a period of erosion. It is believed to have been deposited down a shaft near the center of the cave which then led to the infilling by reddish brown sand and clasts of dolomite and speleothems. The Member 2 sediments are highly fossiliferous, and yield a diverse mammalian fauna including hominins. This unit has also yielded artifacts of a Developed Oldowan or Early Acheulean industry, as well as bone tools.[3] [7] [8] Member 3 was excavated between 1982 and 1986. This infill was formed in a deep gully eroded into Member 1 and 2 deposits. It is mostly noted for the fact that it contains burnt bone, the spatial and temporal distribution of which is suggestive of the controlled use of fire in the cave entrance[8]. This discovery therefore marks the earliest evidence of the controlled use of fire yet identified [2] Member 4 is a largely un-calcified deposit that occupies the northeast corner of the cave, and was deposited under an overhanging roof remnant [9]. It contains abundant Middle Stone Age artifacts but has not yet been excavated[9]. Member 5 is much younger than Member 4, from which it is separated by an erosional disconformity. It forms a 4m thick, lightly calcified deposit on the northwest side of the cave, and has yielded abundant remains of the extinct springbok Antidorcas bondi, from which a radiocarbon age of 11 thousand years (Kya) has been obtained [8].

Age of the deposits

It is difficult to absolutely date the age of South African cave sites nevertheless numerous studies have suggested an age range of between approximately 1 million and 1.5 million years for Members 1 through 3 [2].

Fossil hominin species from Swartkrans

  • Paranthropus robustus
  • Homo ergaster

Important fossil specimens discovered at Swartkrans

  • Sk 48 - P. robustus skull
  • Sk 847 – H. ergaster face

References

  1. 1.0 1.1 R. Broom and J.T. Robinson. (1952). Swartkrans ape-man Paranthropus crassidens. Transvaal Museum Memoir No. 6.. 
  2. 2.0 2.1 2.2 2.3 Hilton Barber, B. and Berger, L.R. (2001). Field Guide to the Cradle of Humankind. Struik. 
  3. 3.0 3.1 3.2 3.3 C.K. Brain (1981). The Hunters or the Hunted?. University of Chicago Press. 
  4. 4.0 4.1 Nigro et al. (2003). Developing a Geographic Information System (GIS) for Mapping and Analyzing Fossil Deposits at Swartkrans, Gauteng Province, South Africa. J Arch Sci. 
  5. L.R. Berger (2005). Working and Guiding in the Cradle of Humankind. Prime Origins. 
  6. L. Backwell and F. D’Errico (2001). Evidence of termite foraging by Swartkrans early hominids.. Proc Nat Acad Sci (USA). 
  7. 7.0 7.1 C.K. Brain (1958). The Transvaal Ape-man – bearing cave deposits. Transvaal Museum Memoir No. 11.. 
  8. 8.0 8.1 8.2 8.3 C.K. Brain (1993). . Structure and stratigraphy of the Swartkrans cave in the light of new excavations. In Brain CK editor. Swartkrans: a cave’s chronicle of early man. Transvaal Museum Monograph No. 8.. 
  9. 9.0 9.1 T. Partridge (2000). . Hominid-bearing cave and tufa deposits. In: Partridge TC, Maud RR editors. The Cenozoic of southern Africa.. Oxford Monographs on Geology and Geophysics.