Veget Hist Archaeobot (1999) 8:199-210
Vegetation History
and Archaeobotany
© Springer-Verlag 1999
The significance of the oil palm (Elaeis guineensis Jacq.) in the late
Holocene environments of west and west central Africa: a further
consideration
M. Adebisi Sowunmi
Department of Archaeology and Anthropology, University of Ibadan, Ibadan, Nigeria
Received June 22, 1998 / Accepted November 5, 1998
Abstract. Abundant archaeological evidence of the occurrence of the endocarp of the oil palm, Elaeis
guineensis, in the rain forest and woodland savanna
zones o f west and central Africa from about 5000 B.P.
has shown the tree to be an important element in the subsistence economy of the region; its pollen also has been
recorded in most o f the regional terrestrial sediments
studied so far. The distinct and consistently sudden and
more marked increases in this pollen during the late
Holocene when compared with the late Tertiary and late
Pleistocene frequencies strongly indicate that the late
Holocene upsurges were due to both natural and human
factors favourable for the expansion of this heliophytic
tree. Reasons are given for suggesting that upsurges in
oil palm pollen during tile late Holocene period in this
region can be used as indices of plant cultivation. While
the oil palm is known from early Tertiary deposits in
west Africa, its earliest palynological record from terrestrial sediments in the west central part dates back only to
the early Holocene. More palynological studies of Tertiary and Quaternary terrestrial cores are required to establish with more certainty the antiquity of E. guineensis
in west central Africa.
Key words: West and west central Africa - Late
Holocene environments - Elaeis guineensis pollen occurrences - Plant cultivation index
Introduction
The word environment is used in the context of this paper to refer to both the human and non-human components as one integral entity, in contrast to the concept of
the environment in which humans are regarded as being
outside of and separate from the physical and other biological components of the environment, for example (cf.
Ingold 1996). The period considered here marks the time
interval between the end of the Holocene climatic optimum (ca. 9000 - 4500 B.P.) and the more notable ob-
scuring, by human activities, of natural environmental
trends. Archaeological and palaeoecological studies in
west Africa have revealed that the late Holocene period
was characterized by significant series of environmental
changes. These changes were brought about by complex
and multiple factors which are as yet incompletely deciphered, though some progress has been made in the last
five years.
Stahl (1993) in a brief review of the Late Stone Age
in west Africa, emphasised how frustratingly meagre the
data were. The scanty evidence available indicate that
human responses to environmental changes were local
and the timing varied from area to area (cf Stahl 1993, p
273). While there were overall "patterns of decreasing
residential mobility; (and) increasing reliance on ceramics", (Stahl 1993, p 272), the inferred changes in subsistence economy differed; thus, in the more southern areas
the subsistence economy was "characterized by continuous reliance on hunting and gathering, perhaps supplemented by arboriculture (for example exploitation of
oleaginous species), horticulture and probably limited
reliance on domestic animals (sheep/goat); . . . . (in contrast) the subsistence base of sites in the Sahara/Sahel
margins ..... " was one "where investment in food production during the last two millennia BC appears to have
been greater...." ( Stahl 1993, p 272). One strikingly recurrent constituent of the subsistence economy in the
southern, forest zone, is the oil palm nut, the charred
endocarps of which have been recovered from several
Late Stone Age rock shelters, in west and west central
Africa, notably: Kokasu and Sopie - Liberia (Gabel
i976), Bosumpra and Kintampo - Ghana, (Smith 1975;
Stahl 1985, 1986), Itaakpa - Nigeria (Oyelaran 1998),
Obobogo - Cameroon (de Maret 1982, 1985), Tchissanga
and Mayumbe, near Les Saras - Congo-Brazzaville
(Denbow 1990; Schwartz 1992; Schwartz et al. 1990),
and Sazuki and Ngovo - Zaire (de Maret 1986). Oil palm
endocarps were found along with the remains of
Canarium schweinJizrthii fruits in some of these cases.
The earliest known record for the exploitation of both E.
guineensis and C. schweinfurthii seeds and fruits seems
to be that from Bosumpra cave, Ghana, with an inferred
date of ca. 5303 ± 100 B.P. (Smith 1975; cf Stahl 1993).
200
Oil palm pollen was found in archaeological layers of a
Late Stone Age rock shelter at Kariya Wuro, north-central Nigeria (Sowunmi and Awosina 1991), while numerous palm kernels, usually cracked open, occurred frequently in gravels o f the Nok valley, associated with indented stones and dimpled hammer stones (Fagg 1959, p
289). It is o f interest to note that the oil palm is today
scarce or hitherto unrecorded as present in the Nok valley or Kariya, respectively.
Palaeoecologieal data on the milieu in which sociocultural changes occurred are even more sparse. One of
the most applicable and direct proxy sets of data come
from the pollen analyses o f terrestrial sites, though inferences can and have been made about developments on
the continent from deep-sea cores taken at varying distances from the coast. But, as recently reiterated by
Jahns (1996, p 207), even though these deep-sea cores
give very long pollen sequences, their time resolution is
much coarser and the provenance of their palynomorph
content more diverse than in terrestrial sediments. The
paucity of palynological data from long and/or continuous sequences o f well-stratified, continental deposits
with fine time resolution is now well-known. For the period and area under consideration, there are 13 such pollen sequences published (Table 1; Fig. 1).These pollen
sequences are from within the present day GuineoCongolian region (White 1983), and indicate that by the
end o f the Holocene climatic optimum the vegetation
still comprised dense rain forest (evergreen/semi-deciduous) and its edaphic or topographic variants. The
present day natural vegetation, disregarding degradation
and other changes caused by various human activities in
the last few centuries, are indicated in Table 1.
a
I(7 . .
•
......-.4
+
-
,
:
i
•.
o.
Just as the oil palm features regularly in the archaeological record o f the period and region under consideration here, so are the pattern of occurrence and prevalence of its pollen significant. E. guineensis pollen has
been recovered from about 85% of the 13 terrestrial pollen sequences mentioned above. The probable palaeoecological and/or anthropological significance of an aspect o f its occurrence was considered by Sowunmi
(1981a, b, c, 1985, 1987), (Talbot et al. 1984), Richards
(1986), Elenga et al. (1992), Elenga et al. (1996), Maley
(1996), and, more extensively, by Maley and Brenac
(1998, in press) and Maley and Giresse (in press). This
important and rather intriguing topic is considered further in this paper, particularly in the context of the light
it might shed on the complex and enigmatic issue o f
plant cultivation and the impact of humans on the rest of
the environment.
The non-human environment
The major features o f late Holocene changes in the
non-human environments are as follows: After the
Holocene climatic optimum, a new phase of dry conditions prevailed in west Africa from ca. 4200-3200 B.P.
This dry phase did not extend to the west central part
until ca. 3000-2000 B.P., by which time wetter conditions had been restored in the former area. The establishment of conditions similar to today's started in west Africa from ca. 3200 B.P., but not until after ca. 2000 B.P.
in west central Africa.
I
i
0°
10"
S
', • t~enln;
i o i
•
i_
1
o°'•
20°
Nigeria
•"
CentralAfrica
03
Rainforest/ grassland mosaic
°~
Rainforest
Gulf of Guinea
Swamp forest
I
6° ~
~
Mangove
1[
Montane forest
Undifferentiatedmontane communities
I
I
I
I
Fig. 1. Map of west and west central Africa showing the vegetation zones of the Guineo-Congolian region (modified after White
1983) and pollen core sites: 1 Lake Bosumtwi, Ghana; 2 Niger delta, Nigeria; 3 Deep-sea core off Niger delta; 4 Mboandong,
Cameroon; 5 Lake Barombi, Cameroon; 6 Bafounda swamp, Bamileke plateau, Cameroon; 7 Shum Laka swamp, Cameroon; 8
Lake Njupi, Cameroon; 9 Lake Ossa, Cameroon; 10 Littoral Congo-Brazzaville; 11 Bilanko depression, Batek6 plateau,
Congo-Brazzaville; 12 Ngamalaka pond, Batek6 plateau, Congo-Brazzaville; 13 Lake Sinnda, Congo-Brazzaville; 14 Lake Kitina,
Congo-Brazzaville
201
Table 1. Late Quaternary terrestrial pollen sequences from west and west central Africa
Location
Altitude
(m asl)
Time interval
(Y.B.P.)
Presentday vegetation
References
Lake Bosumtwi, S central
Ghana
100
ca. 27500-present
semi-deciduous forest
Maley and Livingstone
(1983); Talbot et al. (1984);
Maley (1991); Maley (1996)
Niger delta, SE Nigeria
0.0
>35000-present
coastal strand, mangrove and fresh
water swamp, dense rain forest
Sowunmi (1981a,b,c)
Mboandong, SW Cameroon
120
ca. 6000-present
dense rain forest
Richards (1986)
Bafounda swamp, Bamil6k6
plateau, Cameroon
1310
?-present
submontane evergreen forest
Tamura (1986,1990)
Lake Barombi, SW Cameroon
300
ca. 28000-present
lowland evergreen with patches
of semi-deciduous forests
Maley (1991, 1996); Maley
and Brenac (1998), Maley
and Brenac in press
Shum Laka swamp, Bamenda
highlands, Cameroon
1355
ca. 28700-present
freshwater swamp gallery and
semi-deciduous submontane forests
Kadomura and Kiyonaga
(1994)
Lake Njupi, SW Cameroon
ca. 10001020
ca. 2700-1530
Guineo-Sudan savanna
Zogning et al. (1997)
Littoral Congo-Brazzaville
0.0
ca. 3100-present
littoral savanna
Elenga et al. (1992)
Bilanko, Bat6k6 plateau,
Congo-Brazzaville
ca. 700
>10850-present
woodland savanna with relicts
of rain forest
Elenga and Vincens (1990)
Ngamalaka pond, Bat6k6
plateau, Congo-Brazzaville
ca. 400
ca. 24000-3600;
ca.3300-900
woodland savanna with
relicts of rain forest
Elenga et al. (1994)
Lake Simada, Niari valley,
Congo-Brazzaville
ca. 128
ca. 5240-3990;
ca. 1230-present
wooded grassland, rain forest
Vincens et al. (1994);
Vincens et al. (in press)
Lake Kitina, Mayombe forest,
Congo-Brazzaville
< 700
ca. 5460-present
mixed semi-evergreen forest
Elenga et al. (1996)
Lake Ossa, coastal rain forest,
SW Cameroon
ca. 8.0
ca. 4770-present
dense rain forest
Reynaud-Farrera et al. (1996)
Economic importance, origin, natural distribution,
biology and ecology of the oil palm
Economic importance
The oil palm, Elaeis guineensis, is today a very important tree crop in tropical west and west central African
economies for its numerous products that are o f immense
commercial and domestic value, as sources o f oils and
fats (for domestic consumption, national industries and
export), alcoholic drink (palm wine), fuel, edible nuts,
medicine, animal feed, 'various household and building
materials, as well as their usage for rituals and divination in traditional religion, inter alia. The reddish orange
oil from the pericarp, and, to a less extent, the m u c h
lighter kernel oil, constitute a basic item in the diet o f
peoples in the forest region o f the yam zone (Fig. 2),
where it is almost invariably an essential complement to
yam, one o f the staple foods in the region. The occurrence o f the remains o f the oil palm fruit, sometimes in
great abundance, in several Late Stone Age rock shelters
in west and west central Africa strongly indicates that
the oil-rich fruits and seeds were important in the regional subsistence e c o n o m y . It is o f course difficult to
ascertain what other products o f the tree were also used
in the past, particularly since its charred endocarps appear to have been the only parts preserved in archaeological sites. Evidence from B o s u m p r a cave, Ghana,
suggests that oil pahn nuts were preferred to the other
oleaginous fruits and seeds o f Canarium (Smith 1975). It
is o f interest to note that even today, although Canarium
occurs throughout the forest region o f west Africa, the
only records o f the inclusion o f its fruits and seeds in
peoples' diet, according to Dalziel and Burkill, who have
carried out extensive studies on the uses o f plants in west
tropical Africa (Burkill 1985), are from south eastern
202
and northern Nigeria. In the former area it is significant
that the oil from the outer pulp is not of general acceptance, though in the latter area the seed kernel is eaten
and its oil used as a substitute for shea butter (Burkill
1985, p 303). This suggests that preference for E.
guineensis over Canarium as a food item has had a very
long history.
Origin, natural d&tribution, biology and ecology
There is hardly any doubt now that the oil palm originated in west Africa, as its pollen grains have been recovered from Eocene sediments near Conakry, Guinea
(Zaklinkaya and Prokofyev 1971, cited in Maley and
Brenac 1998), and in Miocene and later Tertiary deposits
in the Niger delta of Nigeria (Zeven 1964).
Although there are isolated occurrences near St.
Louis, Senegal, at 16°N., and in upper Niger, near
Bamako at 13°N, the real palm belt runs from the Fouta
Djallon district of Guinea, through the southern latitudes
of Sierra Leone (right across the southern countries of
west Africa) through to the equatorial regions of CongoBrazzaville and the Democratic Republic of Congo (formerly Zaire); however there are patches in drier areas as
far south as 15°S wherever moisture conditions are favourable. It is normally a palm of lowlands (from 0 to
300 m asl.), but it can also survive, under favourable
moisture conditions, when introduced into highlands and
mountainous areas, as in the Cameroon mountains at
over 1300 m and at 1000 m in the Fouta-Djallon mountains in Guinea (Hartley 1977, pp 5-7; (Fig. 2). As will
be shown later, further palynological studies are required to ascertain when the oil palm became established
in west central Africa.
2o2
10
2O
[
•
I
0
10
/
/-0
~ 1 0
Only relevant aspects of the biology of the oil palm
will be considered here. The oil palm is said to be the
highest yielding oil-bearing plant (Hartley 1977, p i),
and this no doubt accounts for its popularity both in the
past and now. The reproductive cycle is a short one after
the seed has germinated (within two to eight months),
which also makes the tree a very valuable crop. Fruiting
is comparatively early, occurring by the fourth or fifth
year from seed, while the fruits ripen in five to six
months (Corner 1966, p 306). Two other important characteristics of this tree contribute to its being particularly
favoured in forests subjected to fires. First, the seeds
show enhanced germination following a heat treatment
(Purseglove 1972, in Swaine and Hall 1986, pp 65-66).
Secondly, the oil palm is resistant to fire, as the stem
tissues are protected by the persistent, densely-arranged,
woody leaf bases (cf. Swaine 1992, p 372).
The oil palm today occurs naturally in a variety o f
habitats such as forest regrowth (secondary forest)
(Swaine and Hall 1986), river valleys in the forest zone,
(cf. Hartley 1977; Hutchinson and Dalziel 1968), open /
dry forests and gallery forests in savanna (cf. Hartley
1977; Zeven 1967 cited in Swaine and Hall 1986; cf.
Sowunmi 1981a), fresh water swamp forests, (Zeven
1967, cited in Maley and Giresse in press; Hartley 1977),
and margin o f rain forest near transition to savanna
(Letouzey 1978, 1985 cited in Maley and Giresse in
press; Maley and Brenac in press). Since the major characteristic features of oil palm habitats are insolation at
ground level -- unimpeded by forest canopy -- and plentiful but not excessive amounts of moisture, it is not surprising that it is not native to the primeval rain forest (cf.
Hartley 1977, p 4). However, oil palm grows in such a
forest where there are openings, either natural or anthropogenic; hence in modern times, due to the agency of
humans, it flourishes in inhabited areas of an otherwise
dense rain forest, being "particularly abundant in land
which has been tilled" (cf. Hutchinson and Dalziel 1968,
p 161), on farmland, and in derived savannas where it is
also abundant (cf. Sanford and Isichei 1986). The most
continuous and extensive groves are said to be in eastern
Nigeria, in the drier fringes of the pahn belt, (a grove
being an almost pure stand of oil palm, of varying densities, with small shrubs or food crops growing in between
the trees) (cf. Hartley 1977, pp 7, 81).
Palynological record of the p a l a e o g e o g r a p h y
palaeoecology of the oil palm
and
20
oil palm belt
~---2] yam zone
isolated areas of
colonisation
Fig. 2. Presentday natural distribution of the oil palm in Africa. The "palm belt" is shaded; dots represent isolated areas
of colonization (after Hartley 1977: Fig 1.1) The yam zone is
demarcated with broken lines (after Coursey 1976, p 394,
map 1)
A consideration of the palaeogeography and palaeoecology of the oil palm in the region is very relevant to a
discussion on its environmental significance. A very
useful index of these two parameters is the oil palm pollen which has distinctive morphological characteristics.
Reference has already been made here to the occurrence
of these pollen grains in Eocene, Miocene and later Tertiary deposits. One relevant and noteworthy record in the
late Pleistocene to middle Holocene (ca. 150000-6000
B.P.) is from a deep-sea core off the west of the Niger
delta (Dupont and Weinelt 1996). A list of late Holocene
occurrences from terrestrial sediments is given in Table
2, while the geographical distribution from the earliest
203
Table 2. Pattern of occurrence of Elaeis guineensis pollen in the late Holocene period in west and west central Africa
Date (B.P.), inferred climate
Level of occurrence : increase /
decrease (% of pollen sum*)
Locality and country (altitude m asl)
3800 - 3700 dry phase
3200 - 2800 early part of wet phase
2850 - 2700 very dry phase
great increase (0.5 - 23)
great increase (0.0 - 8.3 to 19.1)
first noted occurrence (< 1.0)
2800 - 2400 dry phase
ca. 2500 - 2000 dry phase
first marked increase (0.0 - 1.0 to 8.0 - 10)
ftrst marked increase (< 1.0 to ca. 3.0 - 5.0)
ca. 2500 - 2200 dry (?) phase
first marked increase (0.0 to ca 1.0 - ca. 5.0)
ca. 2300 - 2200 dry phase
ca. 2050 - 1900 end of dry phase/
start of wet phase
ca. 2200 - 1900 end of dry phase/
start of wet phase
ca. 2000 wet phase
ca. 1900 - 1700 early part of wet phase
ca. 2200 - 1600 still dry ? phase
ca. 1900 - 700 (wet phase)
1600 ff. wet phase
1500 - 700 wet phase
first occurrence and increase (0.0 to 2.5 - 3.0)
second, lower increase (0.0 - ca. 1.0)
Lake Bosumtwi, S Ghana (100)
Niger delta, SE Nigeria (0.0)
Ngamalaka pond, Bat6k~ plateau, SE
Congo-Brazzaville (ca. 400)
Lake Barombi, SW Cameroon (300)
Lake Kitina, Mayombe forest, SW CongoBrazzaville (< 700)
Lake Ossa, coastal rain forest, SW
Cameroon (ca. 8.0)
Lake Njupi, SW Cameroon (1000-1020)
Lake Njupi, SW Cameroon (1000-1020)
increase (ca. 2.0 - ca. 5.0)
Mboandong, SW Cameroon (120)
Lake Bosumtwi, S Ghana
Mboandong, SW Cameroon (120)
Lake Ossa (SW Cameroon (8.0)
Niger delta, SE Nigeria (0.0)
coastal Congo-Brazzaville (0.0)
Lake Barombi, SW Cameroon (300)
ca. 800 - 1100 wet phase
low increase (0.5 - 3.0)
great increase (ca. 5.0 - ca. 20)
continued increase (ca. 5.0 - 13.0)
great increase (ca. 6.3 - 24.1)
first occurrence and increase (0.0 - <5.0)
second, more marked increase
(0.0
- ca. 2.0 to 10 - 13)
first occurrence (< 1.0)
ca.
ca.
ca.
ca.
ca.
ca.
major decrease (23 - 0.5)
decrease (ca. 19.1 - 12.0)
major decrease (ca. 10.0 - < 1.0)
decrease (ca. 3.0 - 0.0 to ca. 1.0)
decrease and disappearance (ca. 1.0 - 0.0)
sharp decrease (ca. 3.0 to <1.0)
3000 wet phase
<2800 - 1900 wet phase
2300 - 2100 dry phase
<2200-2050 dry phase
<1900 - 1500 wet phase
<1900 - ca. 1340 wet phase
ca. 1600 - 1000 wet phase
sharp decrease (ca. 13.0 - ca. 5.0).
Lake Sinnda, SW Congo-Brazzaville
(ca.128)
Lake Bosumtwi, S Ghana
Niger delta, SE Nigeria (0.0)
Lake Barombi, SW Cameroon (300)
Lake Njupi, SW Cameroon (1000-1020)
Lake Njupi, SW Cameroon (1000-1020)
Lake Kitina, Mayombe forest, SW CongoBrazzaville (< 700)
Lake Ossa, SW Cameroon (ca. 8.0)
* Pollen sum for Niger delta core different from that in Sowunmi (1981a, b, c) as spores and local pollen are excluded here;
figures for Lake Bosumtwi from Maley J (personal communication 1998)
times to the late H o l o c e n e , as r e v e a l e d b y p o l l e n analysis, is o u t l i n e d in T a b l e 3. A d m i t t e d l y , the data on which
T a b l e s 2 and 3 are b a s e d are v e r y scanty, but these are
the o n l y ones a v a i l a b l e so far.
It is s t r i k i n g l y strange that at the m o m e n t there are no
records from terrestrial s e d i m e n t s o f the o c c u r r e n c e o f E.
guineensis p o l l e n from the m o r e eastern parts o f the region (such as C a m e r o o n and C o n g o - B r a z z a v i l l e ) , p r i o r
to ca. 8000 B.P. when this p o l l e n first a p p e a r e d in d e p o s its at L a k e B a r o m b i - M b o , s o u t h w e s t C a m e r o o n (see Table 3). It s e e m s h i g h l y i m p r o b a b l e that if the oil p a l m
was a l r e a d y p r e s e n t in the natural v e g e t a t i o n o f southern
C a m e r o o n , it w o u l d not have b e c o m e e s t a b l i s h e d along
with o t h e r p i o n e e r t a x a in the d r y p h a s e , ca. 2000014000 B.P., w h e n the f o r e s t b e c a m e m o r e open (cf.
M a l e y 1996). T h r e e other p h e n o m e n a s t r o n g l y indicate
further that the oil p a l m was m o s t p r o b a b l y not a c o m p o nent o f the natural v e g e t a t i o n o f this s u b r e g i o n until the
early to the late H o l o c e n e . First, two o f the w e l l - k n o w n
p i o n e e r s p e c i e s o f forest r e g r o w t h , Musanga-Myrianthus, not o n l y h a d been r e p r e s e n t e d in the lowest l a y e r o f
the Lake B a r o m b i - M b o core, dated ca. 27500 B.P., along
with f o u r others s h o w n in the p o l l e n d i a g r a m , ( M a l e y
and Brenac 1998, Fig. 6) but e x h i b i t e d two large peaks
(16% and 13%) b e t w e e n 27500 and 24000 B.P., and two
s m a l l e r ones (ca.4% and 6%) b e t w e e n 20,000 and 15000
B.P. Second, wetter conditions were restored, b e g i n n i n g
from ca. 10000 until 3000 B.P. D u r i n g that H o l o c e n e interval, g r a s s e s and sedges u n d e r w e n t drastic reductions
while five p i o n e e r taxa s h o w e d several i m p o r t a n t peaks,
a t y p i c a l l y natural r e s p o n s e o f forest r e g r o w t h species.
In contrast, E. guineensis, was the o n l y p i o n e e r species
( o f the seven s h o w n in that p o l l e n d i a g r a m ) which app e a r e d for the first time at ca. 8000 B.P., about 2000
years after the o n s e t o f f o r e s t r e - e x p a n s i o n , b y w h i c h
time conditions w o u l d no l o n g e r be v e r y f a v o u r a b l e for
the natural e s t a b l i s h m e n t o f this h e l i o p h y t i c tree. Third,
if indeed the oil p a h n was present prior to the Holocene,
the a b s e n c e o f its e a s i l y r e c o g n i s e d p o l l e n from the pollen spectra o f o l d e r deposits at b o t h L a k e B a r o m b i - M b o
(cf. M a l e y a n d B r e n a c 1998), a n d N g a m a l a k a p o n d
( C o n g o - B r a z z a v i l l e ) (Elenga et al. 1994), where the ana-
204
Table
3. Occurrence of Elaeis guineensis pollen in west and west central African sediment cores from the Miocene to the Recent
Time period/
Y.B.P.
Locality §
pollen frequency (percentage of pollen sum*)
Eocene
(Guinea) near Conakry
not available
Miocene-Pliocene
Niger delta (Nigeria)
ca.
ca.150000-12000
Deep-sea core, W of Niger delta (Nigeria);
Lake Bosumtwi (Ghana); eastern Niger delta (Nigeria)
ca. <1.0 - 4.0; 0.1 - 1.0; ca. 2.2 - 8.3
ca.12000-8000
Off-shore mangrove peat (CSte d'Ivolre); **
ca.
ca. 8000-5000
Deep-sea core, W of Niger delta; Lake Bosumtwi; Lake
Barombi, Mboandong, (SW. Cameroon); Lake Kitina,
<1.0
Mayombe
forest,
(SW
0.1 - (10)
0.5-1.0; 0.1-0.5;**
- c a . 2 . 0 ; 0.1 - 0 . 5 ; c a . 3 . 0 - 4 . 0 , < 1 . 0
-
ca. 5.0
Congo-Brazzavllle)
ca. 5000-2000
Lake Bosumtwi; E Niger delta; Lake Barombi; Mboandong; ca. 23.0 -3.0; ca. 19.1 - 12.0; 1.0 - 10.0; ca. 2.0 Ngamalaka pond, Bateke plateau, (SE Congo-Brazzaville); 5.0; <1.0 -ca. 5.0; 0.0 -<1.0; 0.0 - ca. 5.0; 0.0 - 0-3.0
Lake Kitina; Lake Ossa (SW Cameroon);
Lake Njupi (SW Cameroon)
ca. 2000-700
Lake Bosumtwi; E Niger delta; Lake Barombi; Mboandong;
Ngamalaka pond; coastal Congo -Brazzaville; Lake
Kitina; Lake Ossa; Lake Njupi; Lake Sirmda (SW CongoBrazzaville)
modem sediments
Deep-sea core, W of Niger delta; Lake Bosumtwi;
E Niger delta; Lake Barombi; Mboandong; coastal
Congo-Brazzaville; Lake Kitina; Lake Ossa; Lake Sinnda
2.0 - 3.0; 12.0 - 24.1; 2.0 - 13.0; 5.0 - 20.0; <1.0; 0.0
< 1 . 0 - 5 . 0 ; 5 . 0 - 13.0; ca. 1.0 -3.0; 0.0 - < 1 . 0
- <5.0;
ca. 13.0; 0.1 - 0.5; 38.7; 5.0; ca. 10.0; 0.0; <1.0; 7.0;
ca. 5.0
§ earliest recorded occurrence so far known in respective countries/locality indicated in bold print;
*pollen sum for Niger delta core different from that in Sowunmi (1981a,b,c) as spores and local pollen are excluded here;
figures for Lake Bosumtwi from Maley (1998, personal communication).
** hiatus in deposit in analyzed Niger delta core
lysed cores extend to the late Pleistocene period, seems
inexplicable. Furthermore, in none o f the other three
Congo-Brazzaville cores which extend to ca. 3100-5460
B.P. did the oil palm pollen occur before ca. 2500 B.P.
(cf. Elenga et al. 1996; Vincens et al. 1994, Vincens et
al. in press; Elenga et al. 1992). A deep-sea core from
near the mouth o f the C o n g o river yielded E. guineensis
pollen in very small quantities (<l.0-ca.2. 0%), discontinuously, from ca. 135000 B.P. to the present (Jahns
1996), but since most o f the p a l y n o m o r p h s were believed to have been wind-borne, the provenance o f the
oil palm pollen cannot be detected with certainty. Indeed
the C o n g o river seemed to have played no part in palynomorph transport as indicated by the absence o f fresh water algae in the core sediments (Jahns 1996, p 208).
Two questions, at least, arise from the evidently late
occurrence o f Elaeis guineensis: first, when was the earliest occurrence o f the oil palm in west central Africa,
second, a s u b - f o r m a t i o n occurs near the northernmost
edge o f the rain forest in southwest Cameroon, at
500-800 m asl, extending for more than 150 km and with
a width o f 10 to 20 km. It is dominated by tall and numerous E. guineensis ( L e t o u z e y 1978, 1985 cited in
Maley and Brenac 1998, p 180). This sub-formation is
regarded as a natural one, primarily because o f the absence o f trees classically linked to man and found in
plantations ( L e t o u z e y 1978, 1985 cited in Maley and
Brenac 1998, p 180; see also R e y n a u d - F a r r e r a et al.
1996; Maley and Brenac in press). W h e n did this subformation develop, and is there sufficient basis for regarding it as natural, particularly in view o f the fact that
human intervention contributed to the development o f
the most extensive groves in the whole o f the region under consideration (Hartley 1977) ?
At the present stage o f study one cannot avoid two
tentative conclusions: first, that the occurrence o f the oil
palm is much more recent in west central than in west
Africa. Second, E. guineensis most probably became established in west central Africa from the early Holocene
onwards, and humans probably played a role in its introduction and expansion there. H o w e v e r , patynological
studies o f terrestrial cores older than 30,000 B.P. and
more extensive archaeological work are required to confirm or refute these conclusions. If confirmed, the conclusions w o u l d have significant palaeophytogeographical and archaeological implications.
205
Pattern o f oil palm pollen o c c u r r e n c e - an index o f
h u m a n activities
Food production in the forest zone of west Africa
One significant threshold in the continuum of interaction
between humans and the rest of the environment has
been the intensified utilization and the augmentation of
plant food resources through cultivation, starting with
the so-called hunter/gatherer-horticulturists (Spriggs
1996). The vast subject of plant cultivation/food production/plant and animal domestication/agriculture is one
which is still a matter of active debate, and about which
much has been written in the last 50 years, not only with
regard to when and how but also what terminologies are
to be adopted for the processes and stages involved (for
recent reviews/contributions on the subject see for example Harris and Hillman 1989; Cowan and Watson
1992; Harris 1996; Leach 1997). With respect to west
Africa, particularly the forest zone, questions relating to
the beginning of plant cultivation remain largely unanswered in the absence of unequivocal botanical evidence, even though there is indirect and rather scanty
evidence, derived mainly from archaeological, linguistic, ethnographic, genetical, and modern phytogeographical data (see, for example, Harlan 1971; Coursey
1976; Flight 1976; Harris 1976; Shaw 1976; Andah
1987, 1993; Harlan 1992; Anquandah 1993; Stahl 1984,
1986, 1993). Over ten years since Stahl (1984, p 20) concluded that evidence in support of either the diffusion or
independent invention hypotheses is equally scanty,
though "... it can no longer be assumed that diffusion is
more likely than independent invention", the situation
has hardly improved. One of the leading archaeologists
in the field of origins and development of food production recently poignantly reflected that we are still far
from understanding how agriculture originated and developed in the continent (of Africa) as a whole (Harris
1997, p 205). However, there seems to be a rather strong,
albeit indirect, indication in support of an indigenous
development of the cultivation of Dioscorea (yams),
perhaps Vigna unguiculata (cowpea), as well as some
form of protection/management of trees with edible
fruits such as E. guineensis, and Canarium sckweinfizrthii.
Two factors which have further compounded the
resolution of the question regarding the early intensification of utilization, cultivation, or domestication of plants
in the forest zone of west Africa, characterized, as
Andah (1993, p 253) reiterated, by root, tuber and
tree-cropping complexes are, first, the paucity of plant
food remains, particularly those of domesticated tubers
in excavated archaeological sites, and, secondly, the oil
palm, an important food crop whose large-scale cultivation began only around A.D. 1860 (Corner 1966, p 304;
cf. Eggert 1993, p 324), is still mostly semi-domesticated, although the reports of human augmentation of
the very limited natural selection in partially domesticated situations were noted in certain localities in C6te
d'Ivoire, Togo and the B6nin Republic (Hartley 1977, p
77).
Preliminary :results from archaeological field experiments at the University of Ibadan, initiated and designed
by Thurstan Shaw and S.G.H. Daniels in 1972, indicate
that it might be possible to find charred remains of yam
tubers in an archaeological context (see Bassey-Duke
1981). The uncovering of such remains would provide
one type of the much-awaited, direct, botanical evidence
of yam cultivation. Indeed, in the humid, tropical
Indo-Pacific region - the subsistence complex of which
is similar,to that of the forest region in west Africa some archaeological remains of charred and uncharred
root and tuber foods have been identified (see Hather
1994).
With regard to the oil palm, it must be admitted that
it is virtually impossible to determine, not to say with
certainty, whether fossil pollen or charred endocarps
from archaeological or nearby sites were derived from
wild or cultivated trees. Hartley (1977, p 5) succinctly
underlined this fact when he said "It is largely speculative and unrewarding (therefore) to consider the presence and spread of the oil palm in Africa in terms of wild
or semi-wild." That being so, how can the pattern of occurrence of its pollen be an index of plant cultivation? It
should be emphasized that what is meant here is not the
cultivation of the oil palm itself, but the practice of cultivation that entails forest clearance. The proposal here
is that part of the answer to this question can be provided
by a careful analysis of the regional pattern of the occurrence of the oil palm pollen from the Tertiary through to
the late Holocene period, as given below.
Pattern of o c c u r r e n c e of oil palm pollen
The suggestion that the pattern of occurrence of oil palm
pollen from the Tertiary through to the late Holocene
period might be used as an index of "palaeo-cultivation"
in west and west central Africa is based on three major
aspects of this pattern: first, the distinct differences between the level of abundance of this pollen in, on the one
hand, pre-late Holocene and, on the other, late Holocene
sediments. Second, a high occurrence synchronously
with independent, archaeological evidence of increased
sedentism and probable practice of cultivation at Lake
Bosumtwi and Kintampo rock shelter respectively (cf.
Talbot et al. 1984, p 184; Flight 1976; Stahl 1985, 1993).
Third, high percentages in modern sediments from the
Niger delta and off the Nigerian coast, eastern Nigeria
being today the region that has the most continuous and
extensive palm groves (cf. Hartley 1977).
The above-listed palynological features are supported by studies which have shown the close association today between oil palm groves and farming
populations or human habitation, as will be elaborated
upon shortly.
O c c u r r e n c e in pre-late H o l o c e n e (before ca 4500
B.P.) and late H o l o c e n e samples
The difference between the pattern of occurrence in
pre-late Holocene and that in late Holocene samples is
indeed striking. Zeven (1964, p 123) provided some
valuable details about the relative abundance of oil palm
pollen in Tertiary sediments of the Niger delta. During
the Miocene, the pollen occurred in very low quantities,
206
I
O_
II
III
IV
V
VI
VII
.~
12_
1000_
VIII
1
2
29_
2000 _
3
3000 _
59_
4
4000 _
74_
5000_
95_ 5b
85_ )a
05_ 5c
6000 _
15_ 5d
7000_
30_
8000BP
ka
5e
6
0
I
I
20 40 20 40
I
I
20 40 20
I
40 20
|
40 20 40
2!
0 40
2
1 I0
%
</.0%
Fig. 3. Collated oil palm pollen diagrams: I Niger delta (based
on data from Sowunmi 1981a ,b, c); II Lake Barombi (from
Maley and Brenac 1998); III Mboandong (from Richards
1986); 1V Lake Kitina (from Elenga et al. 1996); V Lake Ossa
(from Reynaud-Farrera et al. 1996); VI Lake Sinnda (from
Vincens et al. in press); VII coastal Congo-Brazzaville (from
Elenga et al. 1992); VIII deep-sea core west of the Niger delta
(from Dupont and Weinelt 1996) - scales of II - VII modified
for harmonization
about 0.1% of the pollen sum, but showed a tendency to
increase in later Tertiary sediments in which the "frequency occasionally reaches as much as 10% of the total
number of spores and grains" (emphasis by present author). In the late Pleistocene to the early/middle Holocene, the pollen occurred in frequencies of low amplitude, ranging from 0.5 to less than 10% of the pollen sum
and increases were gentle even during the transitions
from arid to wet phases as well as in the wet phases (see
Table 3 and Fig. 3). These low values and gradual increases are in sharp contrast to the higher figures and
abrupt upsurges obtained for the late Holocene during
similar climatic phases; values up to 24.1% were recorded in the Niger delta, for example (see Table 3 and
Fig. 3). How have various authors interpreted the sharp
increases in oil palm pollen during the late Holocene, a
period which coincided in part with the second phase of
the late Stone Age in west and west central Africa, characterized by the use o f pottery, and later, iron technology which was in use from at least ca. 2500 B.P.( Shaw
1990; cf. Fagg 1959; Schwartz 1992) ?
At present, there are three main submissions. The
first (Sowunmi 1981a, b, c, 1985, 1987), suggests that
the marked increases o f E. guineensis in the Niger delta
by about 2800 B.P. were due to forest clearance by humans for the purpose of cultivation, near stream valleys
and in the drier fringes of the forest. This submission
was based on three palaeoecologicat premises: first, a
relative decrease in rain forest trees; secondly, increased
abundance o f fresh water swamp and riverine forests,
which indicates that the rain forest decrease was not
likely to have been due to climatic deterioration; and
thirdly, the concomitant occurrence o f the pollen o f
weeds of. cultivated land or waste places, such as
Borreria verticillata, Aspilia sp., and Cleome ciliata.
Furthermore, on the basis of contemporary archaeological evidence of human occupation, the first occurrence
of oil palm pollen in the pollen records from CongoBrazzaville was attributed to human influence or cultivation. These first occurrences of E. guineensis were
around 2850-2700 B.P. at the Bat6k6 plateau, (Elenga et
al. 1994), ca. 2500-2200 B.P. around Lake Kitina in the
Mayombe forest (Elenga et al. 1996), ca. 1600 B.P., in
the littoral area (Elenga et al. 1992) and ca. 800-1100
B.P. around Lake Sinnda in the Niari valley (Vincens et
al. 1994; Vincens et al. in press). Lastly, ReynaudFarrera et al. (1996, p 754), did concede that after the
natural and important increase in oil palm, which began
ca. 2500 B.P. around Lake Ossa in southwestern Cameroon, its further expansion might have been more and
more aided by human action from about 2000 B.P.
The second submission attributed the increases to
cultivation of plants, including the oil palm. Thus Talbot
et al. (1984, p 185) suggest that the large percentage of
Elaeis guineensis may be due to human cultivation
around Bosumtwi 3500-3000 years ago, on the basis of
two main lines of archaeological evidence: first, the indication from Bosumpra cave, 75 km east of Bosumtwi,
provided by Smith (1975) that the oil palm became an
important food plant in southern Ghana sometime after
5375 :k 100 B.P. and secondly, the deduction by Flight
(1976) that cultivation was practised around 3300-3000
BP. in central Ghana, based on his finds at Kintampo
rock shelter of charred seeds which he believed to be
those of the cowpea.
Richards (1986) reasoned that the cultivation of the
oil palm probably began about 2000 B.P. in southern
Cameroon. His conclusion was based first on the evidence of forest clearance obtained from Mboandong
core, with a dramatic increase of grass pollen, ca. 2380 ~:
70 B.P., which, he implied, was related to the use of iron
implements. Secondly, Richards (1986) opined that the
infrequency of Canarium pollen in contrast to that of
Elaeis in the uppermost levels of the core was consistent
with the cultivation of the oil palm which he presumed
was preferred, as the dwellers of Bosumpra cave in
Ghana seemed to have done (cf. Smith 1975).
The third submission which is a contrast to the other
two, is based on the studies of cores from three lakes in
southwestern Cameroon. According to this view, the occurrence of oil palm pollen, commencing from ca. 8000
B.P. and the two subsequent upsurges ca. 2800-2400
B.P. and ca. 1500-700 B.P. at Barombi, (Maley and
Brenac 1998; Maley and Brenac in press), as well as increases between ca. 2500 and 1900 B.P. at Ossa
(Reynaud-Farrera et al. 1996) and Njupi (Zogning et al.
1997), were due to expansions caused by natural environmental changes and not to the cultivation or domestication of E. guineensis. These natural phenomena were
207
the dry climatic conditions in the late Pleistocene (ca.
20000-10000 B.P.) and late Holocene (ca. 3000-2000/
1600 B.P.), which caused a marked decrease of dense
forests, thus creating spaces favourable for the growth
and multiplication o f this tree and other heliophytes.
According to Maley and Brenac (in press), the two late
Holocene expansions of E. guineensis in Cameroon were
"un comportment tout gtfait naturel". The arguments for
this third viewpoint have been based on four main
grounds: First, 20th century reports o f the natural and
extensive occurrences o f E. guineensis in various parts
of west and west central Africa, particularly the "palm
belt" in the northern fringe of the rain forest in southwest
Cameroon; secondly, the similarity in the pattern of occurrence of oil palm pollen with those of other pioneer
species of forest regrowth or expansion during the early
and late Holocene; thirdly, the current semi-domesticated status of most oil palms, and lastly, the observation by Eggert (1993, p 324) that while the oil palm is
utilized everywhere in the equatorial rainforest of Zaire,
it is never cultivated in a traditional setting (Maley and
Brenac 1998, Maley and Brenac in press).
As already mentioned, it is virtually impossible to
say whether or not the oil palm was cultivated or domesticated in the past. What the pattern of occurrence of its
pollen might indicate is whether or not human influence
contributed to the expansion o f this tree in the late
Holocene. Therefore the question to be considered is as
follows: did the slash-and-burn and swidden cultivation,
adopted in the forest zone, create conditions which prevented the regrowth o f forest trees in openings/clearings,
thus bringing about an anthropogenically enhanced expansion of natural oil palm stands ?
As can be seen from Table 2, there is a consistent
pattern regarding increases in oil palm populations, usually occurring either during a dry phase or at the beginning o f the subsequent wet phase, when forests would
have become more open, creating conditions favourable
for species such as E. guineensis, which colonize forest
openings. There is no doubt therefore that, initially, the
increases in the oil palm would have been a natural phenomenon. But, as indicated earlier, the increases in the
late Holocene, in sharp contrast to those of older deposits, are characterized by being abrupt and large (Table
2). In view of these remarkable differences, it is most
unlikely that the late Holocene increases were due entirely to natural factors. The hypothesis is hereby advanced that an additional factor, the traditional system
of plant cultivation by forest dwellers, with short fallow
periods, contributed in a significant manner to late
Holocene increases in E. guineensis. Consequently, such
characteristic Holocene increases are indicative of plant
cultivation. This indication would be further strengthened by a synchronous occurrence or increase in the pollen of weeds o f farmland or fallow land.
It is of interest to note a somewhat similar phenomenon in the grassfields region of southwestern Cameroon. A pollen analytical study of a core from Shum
Laka swamp showed that even on the return of wetter
conditions after 3000 B.P., grassland still expanded
while the forest declined. The grassland expansion
reached its maximum at about 1600 B.P. (Kadomura and
Kiyonaga, 1994). On the basis of archaeological evidence of human occupation at Shum Laka rock shelter
dating back to about 8000 B.P. (de Maret et al. 1987),
Kadomura and Kiyonaga (1994, p 67) made the tentative
deduction that in the studied area, the process of savanna
creation probably started in the drier period, ca.
3300-3000 B.P., when the vegetation still comprised
woodland or wooded savanna, but that the development
of the present grassland landscape might have started
soon after 3000 B.P. due to human activity, possibly
slash-and-burn agriculture, exacerbated by the use o f
iron implements. The cored site is situated down the
slope from the rock shelter.
The hypothesis made above by the present author is
supported by studies carried out in Zaire, which showed
that in areas where the oil palm occurs naturally, the factor of greatest importance in the development of a grove
was the existence of a dense human population, whilst
groves of varying density grew up where there had been
villages or land cultivated in the past (Hartley 1977, p
78). This is because the practice of forest clearance for
farming created conditions suitable for the rapid establishment of the oil palm, and through constant farming
the development of secondary forest was effectively curtailed. Furthermore, apart from a few exceptions, in the
oil palm region o f west Africa extending from Sierra
Leone to Cameroon, the oil palm is known to have multiplied wherever human population has increased (Hartley
1977, p 78). It should be noted that animals, such as primates and birds, which feed on the palm nut, also contribute to the spread of the oil palm.
Synchroneity of archaeological evidence of cultivation and phenomenal increase in oil palm pollen
The synchroneity between the large increase in oil palm
pollen at Lake Bosumtwi and the archaeological evidence of cultivation from Kintampo rock shelter as first
pointed out by Talbot et al. (1984) has already been
mentioned. Stahl (1985) on a re-excavation of the
Kintampo rock shelter, obtained convincing evidence of
more permanent settlements and of the exploitation of
domestic ovicaprids (sheep/goat) at Kintampo sites as
well as some indirect indication of plant cultivation.
Furthermore, from ca. 3600 B.P., when drier climatic
conditions prevailed, there was a significant shift in the
peoples' diet from arboreal animals to ones characteristic
of open woodland savanna and/or clearings in the forest
(Stahl 1985). Therefore if even the oil palm itself was
not cultivated as Talbot et al. (1984) had inferred, the
natural degradation of the forest coupled with the cultivation of other crops and the building of houses would
have created favourable conditions for the expansion of
E. guineensis whose fruits and seeds the people utilized.
Occurrence in modern sediments
Finally, the hypothesis proposed here, that the characteristic increases in E. guineensis pollen during the late
Holocene can serve as an index of plant cultivation,
though not necessarily of the oil palm itself, is supported
by the high percentages of this pollen in modern
208
sediments. Z e v e n (1964, p 123) noted that in these
sediments the occurrence o f oil palm pollen, which can
be up to 30% o f the total, reflects the cultivation o f the
oil palm as well as methods of land use favourable to its
spread (emphasis by present author). Indeed in the surface sample from the Niger delta the oil palm pollen was
38.7% o f the pollen sum (see Table 3 and Fig. 3). In an
offshore Niger delta core, the value in the surface sample
"which represents the last one or two centuries" was
about 13%, in sharp contrast to the range o f < l . 0 to 4.0%
for the period ca. 150000-6000 B.P. (Dupont and
Weinelt 1996, p 286, Fig. 9) As D u p o n t and Weinelt
(1996, p 286) rightly concluded, this extremely high percentage o f E. guineensis, and the synchronous strong decreases in rain forest and w o o d l a n d vegetations reflect
the impact o f modern agriculture on the vegetation. This
is in accordance with the interpretation given by several
authors, already referred to here, to the marked increases
in oil palm pollen from ca. 3500/3000 B.P. onwards.
Conclusion
Archaeological evidence suggests that the oil palm was
an important and c o m m o n element in the subsistence
e c o n o m y o f peoples in west and west central Africa during the late H o l o c e n e period. The available palynological record has led to the tentative conclusions that the
occurrence o f E. guineensis is much more recent in west
central than in west Africa and that humans most probably played a role in the introduction and / or expansion
of this tree in west central Africa during the late Holocene period. The pattern o f occurrence o f the oil palm
pollen, from the Eocene through the late Holocene to the
present, strongly suggests that the characteristically
marked increases during the late Holocene can be used
as an index o f plant cultivation and, consequently, o f the
contribution o f humans to the expansion o f the oil palm
in both west and west central Africa.
Acknowledgements. This paper was written while the author
was on sabbatical from the University of Ibadan, Nigeria.
Thanks are due to the University of Ibadan for granting this
study leave. The enabling financial and academic support
given by the University of Uppsala, Sweden, University College London, England and Johann Wolfgang Goethe-Universitfit, Frankfurt am Main, Germany, through the initiative of
Professor Paul Sinclair, Professor Peter Ucko and Dr.
Katharina Neumann respectively, is most deeply appreciated.
The conducive environments provided by these and other colleagues at the three institutions contributed immensely to the
production of this paper. I thank Katharina for her constructive critique of the draft of this paper and for valuable discussions. I have also benefitted from discussions with Herr Ulrich
Salzmann. l acknowledge with much gratitude the insights
provided by Dr. Jean Maley and Dr. Annie Vincens both of
whom also made available to me some of their unpublished
papers. I deeply appreciate the time and efforts expended by
Dr. Jean Maley through numerous detailed and very helpful
discussions we had, by correspondence, both before and after
his reading of the draft of the paper. My sincere thanks go to
Frau Barbara Voss for producing the figures.
References
Andah BW (1987) Agricultural beginnings and early farming
communities in West and Central Africa. West African J
Archaeol 17:171-204
Andah BW (1993) Identifying early fanning traditions of West
Africa. In : Shaw T, Sinclair P, Andah B, Okpoko A (eds) The
archaeology of Africa : food, metals and towns. Routledge,
London, pp 240-254
Anquandah J (1993) The Kintampo complex: a case study of early
sedentism and food production in sub-Sahelian west Africa.
In: Shaw T, Sinclair P, Andah B, Okpoko A (eds) The archaeology of Africa: food, metals and towns. Routledge, London, pp
255-260
Bassey-Duk e BE (1981) The experimental archaeological reserve: an experiment in decay at Adesina Oja, Ibadan, Nigeria.
West African J Archaeol 11:53-73
Burkill HM (1985) The useful plants of west tropical Africa, (2nd
edn, vol. 1) ( A revised edition of Dalziel's The useful plants
of west tropical Africa). Royal Botanic Gardens Kew, London
Comer EJH (1966) The natural history of pahns. The University of
California Press, Los Angeles
Coursey DG (1976) The origins and domestication of yams in
Africa. In: Harlan JR, Wet JMJ de, Stemler ABL (eds) Origins
of African Plant Domestication. Mouton, The Hague, pp
383-408
Cowan CW, Watson PJ (eds) (1992) Origins of agriculture: an
intemational perspective. Smithsonian Institution Press, Washington DC
Denbow J (1990) Congo to Kalahari: data and hypotheses about the
political economy of the western stream of the early iron age.
African Archaeol Rev 8 : 139-175
Dupont LM, Weinelt M (1996) Vegetation history of the savanna
corridor between the Guinean and the Congolian rain forest
during the last 150,000 years. Veget Hist Archaeobot 5:
273-292
Eggert MKH (1993) Central Africa and the archaeology of the
equatorial rainforest: reflections on some major topics. In:
Shaw T, Sinclair P, Andah B, Okpoko A (eds) The archaeology
of Africa: food, metals and towns. Routledge, London, pp
289-329
Elenga H, Schwartz D, Vincens A (1992) Changement climatiques
et action anthropique sur le littoral congolais au cours de 1'
Holoc6ne. Bull Soc G6ol France 163 (1): 83-90
Elenga H, Schwartz D, Vincens A (1994) Pollen evidence of late
Quaternary vegetation and inferred climate changes in Congo.
Palaeogeogr Palaeoclimatol Palaeoecol 109 : 345-356
Elenga H, Schwartz D, Vincens A, Bertaux J, Namur C de, Martin
L, Wirrmann D, Servant, M (1996) Diagramme pollinique
holoc6ne du lac Kitina (Congo): mise en 6vidence de
changements pal6obotaniques et pal6oclimatiques dans le
massif forestier
Elenga H, Vincens A (1990) Pal6oenvironnements quatemaires
r~cents des plateaux Bateke (Congo): ~tude palynologique des
d@ots de la d6pression du bois de Bilanko. In Lafranchi R,
Schwartz D (eds) Paysages quaternaires de PAfrique centrale
atlantique. ORSTOM, Paris, pp 271-282
Fagg B (1959) The Nok culture in prehistory. J Hist Soc Nigeria 1
(4): 288-293
Flight C (1976) The Kintampo culture and its place in the economic
prehistory of west Africa. In: Harlan JR, Wet JMJ de, Stemler
ABL (eds) Origins of African plant domestication. Mouton,
The Hague, pp 211-221
Gabel C (1976) Microlithic occurrences in the Republic of Liberia.
West African J Archaeol 6:21-35
Harlan JR (1971) Agricultural origins: centres and noncenters.
Science 174:468-474
209
Harlan JR (1992) Indigenous African agriculture. In: Cowan CW,
Watson PJ (eds) Origins of agriculture: an international
perspective. Smithsonian Institution Press, Washington DC,
pp 59-70
Harris DR (1976) Traditional systems of plant food production and
the origins of agriculture in west Africa. In: Harlan JR, Wet
JMJ de, Stemler ABL (eds) Origins of African plant
domestication, Mouton, The Hague, pp 311-356
Harris DR (1996) Introduction: themes and concepts in the study
of early agriculture. In: Harris DR (ed) The origins and spread
of agriculture and pastoralism in Eurasia. University College
London Press, London, pp 1-9
Harris DR (1997) Book review of Sutton, JEG (ed) The growth of
farming communities in Africa from the equator southwards
(Azania Special Volume 29-30). African Archaeol Rev 14 (3):
201-206
Harris DR, Hillman GC (1989) (eds) Foraging and farming: the
evolution of plant exploitation. Unwin Hyman, London
Hartley CWS (1977) The oil palm. Tropical agriculture series (2nd
edn) Longman, London
Hather JG (ed) (1994) Tropical archaeobotany: applications and
new developments. Routledge, London
Hutchinson J, Dalziel JM (1968) Flora of west tropical Africa (vol
3 part 1) (2nd edn revised by Hepper, FN). Crown Agents,
London
Ingold T (1996) Hunting and gathering as ways of perceiving the
environment. In: Ellen R, Fukui K (eds) Redefining nature:
ecology, culture and domestication. Berg, Oxford, pp 117-155
Jahns S (1996) Vegetation history and climate changes in west
equatorial Africa during the Late Pleistocene and Holocene,
based on a marine pollen diagram from the Congo fan. Veget
Hist Archaeobot 5:207-213
Kadomura H, Kiyonaga J (1994) Origin ofgrassfields landscape in
the west Cameroon highlands. In: Kadomura H (ed) Savannization process in tropical Africa (vol 2), Department of Geography, University of Tokyo, Tokyo, pp 47-85
Leach HM (1997) The terminology of agricultural origins and food
production systems - a horticultural perspective. Antiquity 71:
135-148
Maley J (1991) The African rain forest vegetation and palaeoenvironments during late Quaternary. Climatic Change 19:
79-98
Maley J (1996) The African rain forest - main characteristics of
changes in vegetation and climate from the Upper Cretaceous
to the Quaternary. Proc R Soc Edinburgh 104 B: 31-73
Maley J, Brenac P (1998) Vegetation dynamics, palaeoenvironments and climatic changes in the forests of western Cameroon
during the last 28,000 years BP. Rev Palaeobot Palynol 99:
157-187
Maley J, Brenac P (in press) Les variations de la v6g6tation et des
pal6oenvironnements du sud Cameroun au cours des derniers
millenaires. Etude de l'expansion du palmier h huile. In:
Bilong P, Vicat JP (eds) G6osciences au Cameroun. Publication
Occa-sionelle GEOCAM 1: 1-15
Maley J, Giresse P (in press) Etude d'un niveau argilleux organique
du Mayombe (Congo occidental) riche en pollens d'Elaeis
guineensis et dat6 d'environ 2800 ans BP. Implications pour les
pal4oenvirormements de l'Afrique Centrale. In: Bilong P,
Vicat JP (eds) G4osciences au Cameroun. Publication occasiolmelle GEOCAM 1:1-6
Maley J, Livingstone DA (1983) Extension d'un 616ment montagnard dans le sud du Ghana (Afrique de l'Ouest) au P16istocrne
sup6rieur et ~i l'Holocene inf6rieur: premirres donn6es
polliniques. C R Acad Sci Paris S~r 2 296:1287-1292
Maret P de (1982) New survey of archaeological research and
dates for west central and north central Africa. J African Hist
23:1-15
Maret P de (1985) Recent archaeological research and dates from
central Africa. J African Hist 26:129-148
Maret P de (1986) The Ngovo group: an industry with polished
stone tools and pottery in lower Zaire. African Archaeol Rev
4:103-133
Maret P de, Clist B, Neer W van (1987) R~sultats des premirres
fouilles dans les abris de Shum Laka et d'Abeke au Nord-Ouest
du Cameroun. L'Anthropologie 91:559-584
Oyelaran PA (1998) Early settlement archaeological sequence of
the northeast Yorubaland. African Archaeol Rev 15(1): 65-79
Reynaud-Farrera I, Maley J, Wirrmann D (1996) V6g6tation et
climat darts les frrets du sud-ouest Cameroun depuis 4770 ans
BP: analyse pollinique des s4diments du lac Ossa. C R Acad
Sci Paris S6r 2 322:749-755
Richards K (1986) Preliminary results of pollen analysis of a 6,000
year core from Mboandong, a crater lake in Cameroun. Hull
Univ Geogr Dept Misc Ser 32:14-28
Sanford WW, Isichei AO (1986) Savanna. In: Lawson GW (ed)
Plant ecology in West Africa: systems and processes. Wiley,
New York, pp 95-149
Schwartz D (1992) Assrchement climatique vers 3000 B.P. et
expansion Bantu en Afrique centrale atlantique: quelques
reflexions. Bull Soc G6ol France 163 (3): 353-361
Schwartz D, Foresta H de, Dechamps R, Lafranchi R (1990)
D6couverte d'un premier site de l'fige du fer ancien (2110 B.P.)
dans le Mayombe congolais. Implications palrobotaniques et
p4dologiques. C R Acad Sci Paris Srries 2 310:1293-1298
Shaw T (1976) Early crops in Africa: a review of the evidence. In:
Harlan JR, Wet JMJ de, Stemler ABL (eds) Origins of African
plant domestication. Mouton, The Hague, pp 107-153
Shaw T (1990) The prehistory of west Africa. In: Ki-Zerbo J (ed)
General history o f Africa: methodology and African prehistory.
(vol. 1, abridged edn) Heinemann/UNESCO, London, pp
611-630
Smith AB (1975) Radiocarbon dates from Bosumpra cave, Abetifi,
Ghana. Proc Prehistoric Soc 41:179-182
Sowunmi MA (1981a) Nigerian vegetational history from the late
Quaternary to the present day. Palaeoecol Africa 13:217-234
Sowunmi MA (1981b) Aspects of late Quaternary vegetational
changes in West Africa. J Biogeogr 8:457-474
Sowunmi M A (1981 c) The late Quaternary environmental changes
in Nigeria. Pollen Spores 23 (1): 125-148
Sowunmi MA (1985) The beginnings of agriculture in West
Africa: botanical evidence. Curr Anthropol 26 (1): 127-129
Sowunmi MA (1987) Palynological studies in the Niger delta. In:
Alagoa E J, Anozie FN, Nzewunwa N (eds) The early history of
the Niger delta. Buske, Hamburg, pp 29-64
Sowmmai MA, Awosina EO (1991) Pollen analysis of Kariya
Wuro rock shelter, Bauchi State. Nigerian Field 56 (3-4):
163-170
Spriggs M (1996) Early agriculture and what went before in Island
Melanesia: continuity or intrusion? In: Harris D (ed) The
origins and spread of agriculture and pastoralism in Eurasia.
University College London Press, London, pp 524-537
Stahl AB (1984) A history and critique of investigations into early
African agriculture. In: Clark JD, Brandt SA (eds) Hunters to
farmers: the causes and consequences of food production in
Africa, University of California Press, Berkeley, pp 9-21
Stahl B (1985) Reinvestigation of Kintampo 6 rock shelter, Ghana:
implications for the nature of culture change. African Archaeol
Rev 3:117-150
Stahl AB (1986) Early food production in west Africa: rethinking
the role of the Kintampo culture. Curt Anthropol 27:532-336
Stahl AB (1993) Intensification in the west African Late Stone
Age. In: Shaw T, Sinclair P, Andah B, Okpoko A (eds) The
archaeology of Africa: food, metals and towns. Routledge,
London, pp 261-273
210
Swaine MD (1992) Characteristics of dry forest in West Africa and
the influence of lute. J Veget Sci 3:365-374
Swaine MD, Hall JB (1986) Forest structure and dynamics. In:
Lawson GW (ed) Plant ecology in West Africa: systems and
processes. Wiley, New York, pp 47-93
Talbot MR, Livingstone DA, Palmer PG, Maley J, Melack JM,
Delibrias G, Gulliksen S (1984) Preliminary results from
sediment cores from Lake Bosumtwi, Ghana. Palaeoecol Africa
16:173-192
Tamura T (1986) Regolith-stratigraphic study of late-Quaternary
environmental history in the West Cameroon Highlands and
the Adamoua Plateau. In: Kadomura H (ed) Geomorphology
and environmental changes in tropical Africa: case studies in
Cameroon and Kenya. Hokkaido University, Sapporo, pp
63-93
Tamura T (1990) Late Quaternary landscape evolution in the West
Cameroon Highlands and the Adamoua Plateau. In: Lafranchi
R, Schwartz D (eds) Paysages quaternaires de l'Afrique centrale
atlantique. ORSTOM, Paris pp 298-318
Vincens A, Guillaume B, Elenga H, Fournier M, Martin L, Narnur
C de, Schwartz D, Servant M, Wirrmann D (1994) Changement
majeur de la vSg~tation du lac Sinnda (vall~e du Niari, SudCongo) cons6cutif ~ l'assSchement climatique holocbne
sup6rieur: apport de la palynologie. C R Acad Sci Paris S&ies
2 318:1521-1526
Vincens A, Schwartz D, Bertaux J, Elenga H, Namur C de (in
press) Late Holocene climatic changes in western equatorial
Africa inferred from pollen from Lake Silmda, south Congo.
White F (1983) The vegetation map of Africa. UNESCO, Paris
Zeven AC (1964) On the origin of the oil palm (Elaeis guineensis
Jacq.). Grana Palynol 5:121-123
Zogning A, Giresse P, Maley J, Gadel F (1997) Late Holocene
paleoenvironment in the Lake Njupi area, west Cameroon,
implications regarding the history of Lake Nyos. J African
Earth Sci 24:285-300