Shell beads at three corners of Africa07 Jun 2007
Bouzouggar et al. (2007) report on a series of perforated Nassarius shell beads found in a layer dating to ca. 82,000 years ago in Grotte des Pigeons, Morocco.
The shells are similar to the ones that Marian Vanhaeren found in a drawer of the British Museum last year, from Skhul. Those shells are believed to date to the time of the Skhul fossil series, over 100,000 years ago. At present, they're basically the only evidence of any behavioral difference between the early modern humans from Skhul and Qafzeh and either earlier or later Neanderthal-like people from Tabun, Amud, or Kebara. It's not much, but it's a little.
In last year's paper, Vanharen et al. (2006) also reported a single perforated Nassarius shell from Oued Djebbana, Algeria. The date was unknown, believed by radiocarbon to be older than 35,000 years. That followed after the discovery of 41 Nassarius shell beads from Blombos, South Africa (Henshilwood et al. 2004). Although there were doubts with those finds (expressed in news stories by Michael Balter and Constance Holden), the Blombos finds are quite compelling:
Small objects may easily be displaced through archaeological layers, and perforated tick shells were also recovered at Blombos Cave from the more recent LSA layers. OSL measurements on 1892 individual quartz grains from the aeolian sand layer that separates the LSA and MSA levels (6) indicates no contamination by grains of different ages, contraindicating downward percolation of younger objects. Also, MSA beads are significantly larger (P < 0.0001) than those from LSA levels; the most common MSA perforation type is present on <1% of the LSA shells; LSA beads do not have the wear facets found on MSA specimens; and only 5% of MSA beads have broken lips, compared to 52% of LSA beads, suggesting that the latter were strung in a different way. MSA beads are dark orange or black, whereas those from the LSA are white or pale beige (fig. S1). MSA shells were found in clusters of 2 to 17 beads, with each group clustering in the same or neighboring 50-by-50-cm quadrates. Within a group, shells display a similar size, shade, use-wear pattern, and perforation size. Each cluster may represent beads coming from the same beadwork item, lost or disposed during a single event (Henshilwood et al. 2004:404).
There is perhaps a question as to whether the holes might represent eating the gastropods inside the shells rather than stringing them, but the Blombos beads appear to have been colored by red ochre or put in contact with other objects that were.
The collection from Grotte des Pigeons is not quite as numerous as the Blombos sample (with only 13 shells recovered), but like Blombos, they are in situ and with fairly clear associations. Also, Bouzouggar et al. can give pretty good detail about why humans had to bring them and how they were made:
The N. gibbosulus shells certainly were brought to the site by humans. The local dolomitic bedrock is too old to be a source, predating the origin of the species (36). The distance from the site to the contemporary coast could not have been <40 km (37), too far for natural processes known to carry marine shells inland, such as animal predators or major stor ms (38). It also is clear that the N. gibbosulus were not intended for human consumption because all show features characteristic of dead shells accumulated on a shore. These features include encrustations produced by bryozoa, tiny shells, and sea-worn gravel embedded into the body whorl and perforations produced by a predator on the ventral side of the shell (SI Fig. 7). Comparison with the perforation pattern recorded on a modern thanatocoenosis of this species reveals that the Taforalt [i.e., Grotte des Pigeons] shells do not represent a random selection from a natural assemblage of dead shells (Fig. 5). None of the archaeological examples is undamaged, whereas almost half of those from the comparative sample are intact, and the perforation type most common on the archaeological specimens is rare in nature. This type, a single perforation on the dorsal side at the center of the last spiral whorl, is observed in only 3.5% of the comparative sample; the probability of randomly collecting a sample of shells like that from Taforalt is extremely low (P 0.0001), which suggests that the shells with a perforation on the dorsal side were either deliberately collected or perforated by humans. Although the latter seems more probable, the agent responsible for the perforations cannot be firmly identified. Microscopic features diagnostic of human intervention in the production of the perforation are absent (39). Hole edges on the dorsal aspect are rounded and smoothed on four shells. The remainder have irregular outlines with chipping of the inner layer, indicating the agent responsible for the perforation punched the shells from the outer dorsal side. Holes with irregular edges may be obtained by punching the dorsal side with a lithic point (2, 11). Smoothed hole edges have been replicated by wearing str ung modern shells (39). Both types of hole edges occur on shells used as beads in Upper Paleolithic sites (40)....
Possible evidence for the stringing of the perforated shells as beads comes from the identification on ten specimens of a wear pattern different from that observed on both the modern reference collection and unperforated specimens from Taforalt. The wear in the latter case homogeneously affects the whole surface of the shells and consists of a microscopic dull smoothing associated with micropits and rare short, randomly oriented striations. The wear on the presumed strung examples is found on the perforation edge and on spots of the ventral and lateral side, and it is characterized by an intense shine associated with numerous random or consistently oriented striations (Bouzouggar et al. 2007:9966-9967).
Like the Blombos shells, a number of those from Grottes des Pigeons preserve "residue" of pigment on their surfaces:
The most likely explanation for the presence of pigment on the shells is their rubbing against material embedded with ocher, such as hide, skin, thread, or other substance. We can rule out accidental causes because in two specimens colorant is stuck in microcracks that cross the worn area, indicating that wear and coloring werre intertwined processes. No other objects (e.g., artifacts or bones) from these deposits carry similar pigments, nor are there obvious particles of natural ochres/ores in the sediments (Bouzouggar et al. 2007:9968).
So here, the critical evidence is that (a) the shells were dead when collected; (b) they were transported by people over 40 km from the shore to the cave; (c) they were worn by stringing; and (d) they were colored with pigment, directly or by contact with something also worn and pigmented.
I don't know that you can do much better than this, unless you find them draped across the neck vertebrae of a skeleton.
What is notable about this? I would say, more important than the date (with now three sites clearly over 70,000 years) is the geographic extent of the perforated shells. Africa is a big continent, and now there are shell beads from the three furthest corners of it (Israel being just above the northeast corner). This suggests a very widespread diffusion or dispersal of shell bead-making; yet the Middle Stone Age was a time of increasing regional distinctiveness of technological industries within Africa. If North, South, and East Africa had different traditions, why did they share beads made from these particular shells -- and in two instances, at least, colored red?
Balter M. 2006. First Jewelry? Old shell beads suggest early use of symbols. Science 312:1731. doi:10.1126/science.312.5781.1731
Bouzouggar A and 14 others. 2007. 82,000-year-old shell beads from North Africa and implications for the origins of modern human behavior. Proc Nat Acad Sci USA 104:9964-9969. doi:10.1073/pnas.0703877104
Henshilwood C, d'Errico F, Vanhaeren M, van Niekirk K, Jacobs Z. 2004. Middle Stone Age shell beads from South Africa. Science 304:404. doi:10.1126/science.1095905
Holden C. 2004. Oldest beads suggest early symbolic behavior. Science 304:369. doi:10.1126/science.304.5669.369
Vanhaeren M, d'Errico F, Stringer C, James SL, Todd JA, Mienis HK. 2006. Middle Paleolithic shell beads in Israel and Algeria. Science 312:1785-1788. doi:10.1126/science.1128139