Aspects of African Archaeology
Shum Laka rock shelter late Holocene deposits: from
stone to metal (North Western Cameroon)
This paper deals with the transition from the Final Late Stone Age (LSA) to the Iron Age at Shum
Laka rockshelter from a technological and typological point of view. Some time ago it was proposed
to call this transition the "Stone to Metal" Period (SMP), implying that it is still very poorly
understood in West and Central Africa (McIntosh and McIntosh 1988; Maret 1994, this volume).
The Holocene deposits at Shum Laka are by far the richest archaeological layers of the site.
Two members can be distinguished:
• the ochre ash layer, dated between 9000 and 6000 BP, which yielded a LSA assemblage.
• the grey ash layer, dated from 4000 BP to historical times, which yielded "Stone to Metal"
and Iron Age assemblages.
The ochre ash layer
The study of the archaeological material of the ochre ash layer is preliminary. The sample
analyzed, coming from two test squares, is small (2117 artifacts) and all results presented here
should be considered with caution.
The ochre ash layer yielded a lithic industry without pottery. To the same occupation phase are
ascribed three burials (Maret, this volume).
As in the underlying deposits (Cornelissen, this volume), four locally available raw materials
were used, mainly quartz (59%) and basalt/welded tuffs (36%). To a lesser extent various silicates
(calcedony, jasper, chert, de vitrified lava, breccia and obsidian) (3%) were also flaked. Sandstone is
present (2%) (Table 1).
Regardless of the raw material most of the industry is composed of unmodified waste (more
than 99%). Only four unspecialized quartz cores were identified. One can hardly speak of a toolkit:
it consists of one large retouched basalt flake and one scraper re-flaked on a polished basalt fragment.
The Holocene Final LSA of the ochre ash layer can at best be characterized as an un standardized
industry. It is quite similar to the Pleistocene LSA except for basalt and welded tuffs becoming
more common. Further analyses will tell whether it may indicate the onset of an evolution towards
266 Philippe Lavachery
Table 1 Lithic material from the Holocene deposits.
Lavers Ochre ash
Chips and chunks 699
1 platform cores
> = 2 platform cores
Modified pieces 1
Shaped tools 1
Bifacial core tools
Frag. bifacial core tools
Bifacial flake tools
Unifacial flake tools
Flakes scrapers 1
Unmodified waste 1.242
Chips and chunks 1.202
1 platform cores 1
> = 2 platforms cores
Casual cores 3
Unmodified waste 73
Chips and chunks 61
1 platform cores
> = 2 platforms cores
Unmodified waste 44
Chips and chunks 44
Lower srrev ash UDDer srrav ash
Shum Laka rock shelter late Holocene deposits: from stone to metal (North Western Cameroon) 267
The grey ash layer
The actual shift from microlithism to macrolithism occurred between 6000 and 4000 BP. Unfortunately
a chronological gap of some 2000 years between the ochre and grey ash layer occupations
prevents us from understanding exactly how it took place. At the base of the grey ash a macrolithic
industry with pottery appears.
Three occupation phases were identified:
• the "Stone to Metal" Period (SMP), located at the base of the layer, is dated from 4000 to 3000
BP. It yielded an abundant lithic industry and some pottery. Four burials are associated to that
occupation phase (Maret, this volume).
• the Early Iron Age (EIA), situated in the middle part of the grey ash, is dated between 2000
and 1300 B , P. The assemblage is composed of lithic material, some iron objects and pottery.
• the Late Iron Age (LIA) lies in the upper part of the grey ash and is dated from 900 BP to
recent times. It yielded lithic material and pottery.
These phases are clearly stratified on top of one another in certain areas of the site and radiocarbon
dates are in the right stratigraphical order (Moyersons, this volume). It is quite surprising,
however, that the stone industry should survive into the Late Iron Age. The distribution of the lithic
material is quite homogeneous throughout the whole layer up to the surface without any obvious
typological evolution. This phenomenon is understandable if we study in some detail the postdepositional
processes which left traces in the archaeological evidence. It is important to remember
that the ash, of which the ancient surface was higher than today at the back of the shelter, was
certainly truncated by erosion several times between 2000 BP and 1000 BP and that very little
sedimentation took place afterwards (Moeyersons, this volume). All deposits younger than 2000
BP, thus post-dating the erosion phase, may then be deeply reworked. Only the base of the grey ash
layer is certainly.in situ.
The SMP occupation phase
The sample studied here (33647 artifacts) comes out of fourteen squares where the SMP occupation
phase is well identified. Four raw materials were used: basalt and welded tuffs are now predominant
(6 1 %), followed by quartz (3 1 %) and silica (8 %). Regardless of the raw material most artifacts
(more than 97%) are unmodified waste (Table 1).
Cores represent between 0.2 and 1.8% of the debitage. Most of them are flake-cores and display
non-specialized flaking techniques but some basalt blade-cores (Fig. 2.5) were also identified.
Blade production is thus attested and 6% of basalt/tuff flakes are blades (LIW?2). Most of them
have parallel dorsal ridges and parallel or convergent sides but some basalt/tuff flakes and blades
display a triangular flaking pattern resulting in a triangular shape reminiscent of Levallois points.
Basalt blades and points are the product of a carefully prepared flaking process, contrary to the
rest of the flake population. Are those triangle flakes the result of a specialized manufacturing
process distinct from the blade technology? It is beyond the scope of this paper to discuss the
concept of the Levallois technique but it is probable that points may result from blade technology
rather than Levallois technique sensu stricto. Both flake types share many technological features
(such as proportions, shape, striking platform preparation) and there is an obvious morphological
continuity between blades and points (Fig.2: 1-4).
The SMP toolkit is largely composed of basalt and welded tuff heavy duty tools. Tools represent
0.4% of the basalt/tuff industry. Half of them are core tools which are mainly bifacially trimmed.
Some are typical waisted "axes" (Fig. 1 : 1 ,2) which are sometimes partially polished (Fig. 1 :5), some
268 Philippe Lavachery
Figure 1 Stone to Metal Period lithic material.
o 1 2cm
Shum !..aka rock shelter late Holocene deposits: from stone to metal (North Western Cameroon) 269
Figure 2 Stone to Metal Period lithic material and pottery.
o 1 2cm
270 Philippe Lavachery
other examples look like crude hand-axes, core-axes, foliates (Fig. I :3,4,6) and even chopping tools.
Flake tools are mostly scrapers and retouched blades or triangular points (Fig.2: 11,12). Quartz and
silica tools are much less common (0.04 and 0.4% of the industry). Most of them are small backed
silica flakes of which some are microlithic (Fig.2:.6-9). Microlithism seems to be a survival of a
LSA tradition but it now concerns only 10% of the toolkit. It is interesting to note that a good part of
the macrolithic component of the SMP toolkit is typical of what was usually attributed to supposedly
much older Middle Stone Age industries in West and Central Africa: i.e. rough bifacial tools,
core-axes and "Levallois" points.
A preliminary analysis has been carried out on SMP pottery. All sherds, which were found
clustered in a very small area, belong to the bottom of the same pot. Its very thick base is flattened
and the clay is rather coarse. Unfortunately nothing is known about its decoration (Fig.2: 10).
The early and late Iron Age occupation phases
In the middle part of the grey ash layer early Iron Age artifacts make their appearance.
One fragment of an iron bracelet and one iron finger ring were found in 1982 (Asombang
1988). In the same levels, pottery, now much more common and much finer, is decorated with
impressions of elaborate carved wooden roulettes (Fig.3: 1,2,5,6), incisions and grooves.
The upper part of the layer yielded late Iron Age pottery decorated with impressions of knotted
strip roulette, twisted string roulette, simpler carved wooden roulettes (Fig.3:.3,4), incisions and
The lithic industry associated with the early and late Iron Age assemblages (19579 artefacts)
shows both similarities and differences with the lower SMP assemblage:
• on the one hand the types of large tools, cores, blades and points remain similar aithough they
become extremely rare in the two Iron Age horizons.
• on the other hand a completely ground adze with a polished cutting edge (Fig.3.7), very
different from the SMP core tools, was found in a recent layer overlying the SMP levels.
• the proportion of broken and re-flaked stone artifacts is higher in the Iron Age levels than in
the SMP levels.
• artifacts become increasingly smaller from bottom to top of the grey ash layer.
Spatial patterning and interpretation of the stratigraphy
The refits of pottery sherds allowed me to understand the spatial relationship between the three
occupation phases in the grey ash layer and their dynamics. Refits revealed that a fair amount of
disturbance took place throughout the whole shelter in the middle and upper parts of the grey ash.
These disturbances were probably the result of both erosion and anthropic occupation. The lower
part of the layer, however, is not disturbed since the SMP pottery sherds were found clustered.
Moreover, no sherd refits link the SMP and Iron Age levels. EIA sherds, on the contrary, are found
in both the middle and upper parts of the grey ash while LIA sherds are systematically limited to the
upper part of the layer. Since we have seen that the ancient surface which was higher than today at
the back of the shelter was truncated by erosion between 2000 and 1000 BP, the presence of EIA
sherds at the actual surface is not a surprise. But can the same be said about the stone industry? Does
it belong to the iron age levels or is its association with the iron age also a result of a post-depositional
Shum Laka rock sh elter late H o I ocene d eposits' F..
. Jlom stone t o metal (lI.T
Figure 3 Early and L ate Iron A ge pottery and ground adze.
rrestern C ameroon)
272 Philippe Lavachery
A cluster of large SMP basalt artefacts and small rocks was found in the lower part of the grey
ash. The same cluster surfaces at the back of the shelter where it is found mixed with iron age
material. In order to explain this clustering of large pieces an analysis of the spatial patterning of the
stone artifacts according to their size was conducted. This revealed a regular increase of the propor
tion of small artifacts from the back to the entrance of the shelter. Most likely erosion evacuated not
only sediments but also a good part of the smallest artifacts from the back to the entrance. Thus the
small artifacts found in the sediments younger than 2000 BP, post-dating the beginning of the ero
sion phase and associated with iron age pottery, would therefore be older material coming from the
eroded top of the SMP levels. This explains why lithic artifacts of the iron age deposits are smaller
than those of the SMP deposits which are still in situ. The cluster of large artifacts in the lower part
of the grey ash results from the accumulation of large pieces on the erosion surface when the fines
and the small objects were washed away.
The people of the early Iron Age certainly still used stone tools occasionally. The few large
SMP type artefacts discovered in the Iron Age levels could have been intentionally picked up by
them from the SMP cluster surfacing at the back of the shelter. Their use as raw material and/or
expedient tools would explain the higher proportion of broken and re-flaked artifacts in the Iron
Age levels. Unfortunately, due to this combination of natural and human disturbances an Iron Age
stone industry cannot be singled out anymore.
Conclusion: cultural changes in West and Central Africa through Late Holocene
The study of the Holocene deposits of the site of Shum Laka is a very good reminder of the danger
of interpreting the significance of non-stratified assemblages in West and Central Africa. Firstly it
shows that it is only by identifying site formation processes that one is able to assertain the cultural
value of archaeological assemblages. This is possible only in stratified sites. Secondly it shows that
typology can be seriously misleading in the absence of stratigraphic context and radiocarbon dates.
The macrolithic component of the SMP industry of Shum Laka displays many characteristics of a
Middle Stone Age industry but it is clearly Holocene.
The appearance of pottery and polished macrolithic stone tools on the old LSA substrate be
tween 5500 and 2500 BP is widespread in West and Central Africa. The proportion of microliths
surviving in those new assemblages, however, seems to be very variable. The oldest sites, dated
around 5500 and 5000 BP, are all rockshelters situated between the Cameroonian Grassfields and
Ghana. Among them are Abeke (Maret et al. 1987) in north-western Cameroon, Iwo Eleru (Shaw
and Daniels 1984) and Afikpo (Hartle 1980) in Nigeria and Bosumpra (Shaw 1944; Smith 1975) in
Ghana. That area, corresponding to the region where indigenous African yarn was first domesti
cated (Harlan 1992), seems to be the sub-Saharan cradle of the phenomenon. Although we do not
know if early SMP populations actually cultivated yam, they already intensively exploited Elaeis
and were still hunters. Before 3500 BP comparable assemblages had reached all West Africa, such
as Shum Laka (Maret et al. 1987) and Mbi Crater (Asombang 1995) in north-western Cameroon,
Rim (Andah 1978) in Burkina Faso and Yengema (Coon 1968) in Sierra Leone.
From 3500 to 2500 BP the process enters a new phase. In West Africa Saharan influence may
be seen in pottery and stone arrow heads. The populations lived permanently in villages built on
mounds or in rock shelters as is the case for the Kintampo Complex sites in Ghana (Flight 1976;
Stahl 1985, 1993; Kense 1993) and the Borno mounds in the Lake Tchad region (Connah 1981;
Breunig et al. 1993). In Central Africa most of the first SMP assemblages are found in open-air sites
consisting of groups of large pits which are remnants of villages. Examples are Obobogo (Maret
1990) in southern Cameroon, Okala (Clist 1989,1995) in Gabon and Sakuzi (Maret 1990) in Lower
Zaire. Most of these sites, although indicating increased sedentism, semi-domestication of Elaeis
Shum Laka rock shelter late Holocene deposits: from stone to metal (North Western Cameroon) 273
and animal husbandry, hardly yield any lithic artifacts at all. Therefore it is highly probable that the
final SMP popUlations were already metal users. And indeed, around 2500 BP iron smelting tech
nology is attestedjn the Nok Culture of Nigeria (Fagg 1968) and in Gabon (Clist 1989, 1995).
It must be stressed that since LSA, SMP and even EIA sites are sometimes contemporaneous in
the area considered, these terms should refer to techno-complexes and not to actual chronological
phases. The transition from the aceramic LSA to the Iron Age, implying technological, economical
and social changes, was certainly a very progressive and complicated process.
In this regard Shum Laka rock shelter may contribute substantially to the understanding of how
and when the transition from the LSA to the Iron Age first took place. The cultural sequence shows
that macrolithism, a few surviving microliths and ceramic are diagnostic features of the early SMP
in the Grassfields area.
The research was made possible by grants from the Belgian National Fund for Scientific Research,
the L.S.B. Leakey Foundation, the Royal Museum of Central Africa and the University of Brussels.
We would like to thank the authorities of Cameroon for research clearances and the Fon of Bafochu
Mbu for letting us conduct excavations at Shum Laka. We are indebted to the numerous people who
assisted us in the field and provided logistical support. We would also like to thank Dr. W. Van Neer
for the bone identifications, Dr. 1. Maley for the pollen analysis, Mr. H. Doutrelepont for the char
coal identifications, Ms. 1. Ribot for the study of the human remains and Ms. Y. Pacquay for the
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