Climate change, genetics or human choice: why were the shells of mankind’s earliest ornament larger in the Pleistocene than in the Holocene?

Teske, P.R. and Papadopoulos, I. and McQuaid, C.D. and Newman, B.K. and Barker, N.P. (2007) Climate change, genetics or human choice: why were the shells of mankind’s earliest ornament larger in the Pleistocene than in the Holocene? PLoS ONE, 2 (7). ISSN 1932-6203



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The southern African tick shell, Nassarius kraussianus (Dunker, 1846), has been identified as being the earliest known ornamental object used by human beings. Shell beads dated from ~75,000 years ago (Pleistocene era) were found in a cave located on South Africa's south coast. Beads made from N. kraussianus shells have also been found in deposits in this region dating from the beginning of the Holocene era (<10,000 years ago). These younger shells were significantly smaller, a phenomenon that has been attributed to a change in human preference. We investigated two alternative hypotheses explaining the difference in shell size: a) N. kraussianus comprises at least two genetic lineages that differ in size; b) the difference in shell size is due to phenotypic plasticity and is a function of environmental conditions. To test these hypotheses, we first reconstructed the species' phylogeographic history, and second, we measured the shell sizes of extant individuals throughout South Africa. Although two genetic lineages were identified, the sharing of haplotypes between these suggests that there is no genetic basis for the size differences. Extant individuals from the cool temperate west coast had significantly larger shells than populations in the remainder of the country, suggesting that N. kraussianus grows to a larger size in colder water. The decrease in fossil shell size from Pleistocene to Holocene was likely due to increased temperatures as a result of climate change at the beginning of the present interglacial period. We hypothesise that the sizes of N. kraussianus fossil shells can therefore serve as indicators of the climatic conditions that were prevalent in a particular region at the time when they were deposited. Moreover, N. kraussianus could serve as a biomonitor to study the impacts of future climate change on coastal biota in southern Africa.

Item Type:Article
Additional Information:Copyright Teske et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Citation: Teske PR, Papadopoulos I, McQuaid CD, Newman BK, Barker NP (2007) Climate Change, Genetics or Human Choice: Why Were the Shells of Mankind’s Earliest Ornament Larger in the Pleistocene Than in the Holocene? PLoS ONE 2(7): e614. doi:10.1371/journal.pone.0000614
Uncontrolled Keywords:Nassarius kraussianus; southern African tick shell; shell size; climate change; environment; phylogeographic history; genetic lineages; haplotypes; fossil shells;
Subjects:Y Unknown > Subjects to be assigned
Divisions:Faculty > Faculty of Science > Botany
Faculty > Faculty of Science > Zoology & Entomology
ID Code:806
Deposited By: Mrs Eileen Shepherd
Deposited On:31 Aug 2007
Last Modified:06 Jan 2012 16:19
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