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Humans and oil palm (Elaeis guineensis Jacq.) exploitation in Orile-Owu, Southwest Nigeria, ca. 1450-1640 A.D: Archaeo-botanical evidence

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Abstract
Exploitation of the oil palm is one of the chief sources of livelihood for the people of Orile-Owu, southwest Nigeria,
and generally the forest zone of West Africa. Research has established that the exploitation of this important tree
crop in West Africa stretches back to more than 5,000 YBP (years before present). However, there is little data on
its antiquity at Orile-Owu. Therefore, this research aims to present the rst direct archaeo-botanical evidence
for the antiquity of the utilisation of the oil palm in Orile-Owu. Archaeological investigations and pollen analysis
were carried out in Orile-Owu. The excavation conducted in March 2013 on a mound in Orile-Owu produced an
abundance of potsherds, charred and uncharred palm kernels, lithic: non-tools (granite, quartzite and geothite),
charcoal, indeterminate broken tooth, animal bones, a sandstone bead and a rusted knife. An AMS radiocarbon
date of ca AD 1450-1640 (Beta-403755) was obtained from charred palm kernel endocarp at the lowest cultural
level (60-70 cm) where a high concentration of the oil palm pollen was encountered. The occurrence of palm kernel
endocarps in association with potsherds and charcoal fragments indicated human occupation at that level, whilst
evidence for the burning of vegetation probably preparatory for farming may indicate a possible exploitation
of the oil palm for at least the last 500 years. The interpretation given here is further strengthened by the high
percentages of oil palm pollen (≥ 25%) in most levels along with an increase in microcharcoal particles and a
corresponding general paucity of the pollen of lowland rain forest species.
Introduction
Archaeological and palaeoecological studies have revealed
that the exploitation of the oil palm in Nigeria and generally
in West Africa has had a long history of over 5,000 YBP
(Sowunmi 1999), although there is disagreement amongst
scholars on its origin. Whilst it has been contended that the oil
palm originated in South America from the upper Amazonian
region (e.g Barcelos et al. 2002) other authors argue for a West
African origin (e.g. Sowunmi 1999; Zeven 1964). Substantial
palynological evidence has indicated that the origin of the
oil palm can be narrowed down to West Africa because the
earliest occurrence of the pollen of the oil palm has been
recovered from Eocene deposits near Conakry, Guinea
(Zaklinskaya and Prokofyev 1971 cited in Maley and Brenac
1998) and in Miocene sediments in Elelenwa, Niger Delta of
Nigeria (Zeven 1964). The hypothesis on the South American
origin still remains unclear (Barcelos et al. 2002).
In July 2012 and March 2013, archaeological investigations
were conducted in Orile-Owu, one of the many Owu
communities situated in the southwestern part of Nigeria.
Primordial Owu is one of the earliest and most important
amongst the several city states in which the Yoruba speaking
people are found (Mabogunje and Omer-cooper 1971). The
Owu people are notable warriors who are hardy, brave and
courageous (Johnson 1921). They are said to be very powerful
and among the few peoples who fought against slave trading
(Mabogunje and Omer-cooper 1971). However, during the
internecine war in the early part of the nineteenth century,
this formidable Yoruba town was sacked by the allied forces of
Ife, Ijebu and Oyo (Akintoye 2010). The outbreak of war led
to the wide dispersal of the people of Owu into neighbouring
14
communities. The Owu in diaspora formed local Owu
communities wherever they went and this is why we have
small Owu communities scattered around dierent parts of
Nigeria of which Orile-Owu is one such communities.
The archaeological investigations in Orile-Owu entailed
reconnaissance and excavation. The research was prompted
by the need to determine the antiquity of oil palm
exploitation in Orile-Owu after noting the signicance
of the oil palm to the present-day inhabitants of Orile-
Owu in the course of reconnoitering the area. The aim of
the investigation was to provide insights into the cultural
histories of the people, their antiquity in the area and their
subsistence economy through time. This paper, motivated
by recent radiocarbon date from Orile-Owu, focuses on the
subsistence economy of the people. The paper sheds light
on the importance of the oil palm to the present-day settlers
of Orile-Owu and attempts from archaeo-botanical data to
reconstruct the time depth of the exploitation of the oil palm
in Orile-Owu.
Among the important indigenous food crops in the southern
part of West Africa, where Nigeria is situated, are yams
and the oil palm, which have been exploited simultaneously
(Sowunmi 1985, 1999). Nevertheless, the scope of this paper
covers only the oil palm. The oil palm is a very important
tree crop in Orile-Owu, largely due to exploitation of a range
of its products for commercial and domestic purposes. At
present, it gives the highest yield of oil of all the oil producing
trees (Corley and Tinker 2003). Apart from the palm fruit
which is the major source of oil, virtually every other part
of the tree can be used. Other products from the palm tree
include alcoholic drink (palm wine), edible nuts, medicine,
fuel, animal feed and the palm oil product is also used as
part of the concoction for rituals and divinations (Sowunmi
1999). Despite the immensity of oil palm usage in Orile-Owu,
we lack an understanding of the earliest period when the
inhabitants of Orile-Owu began to exploit this versatile tree
crop. This paper therefore, presents the rst direct archaeo-
botanical evidence thus far recorded for the possible antiquity
of the exploitation of the oil palm in this region. Since
archaeological research in the southwestern part of Nigeria
has revealed that the oil palm have been exploited for over
2,000 YBP (e.g Alabi 2000, 2002; Oyelaran 1991, 1998), this
research seeks to situate the exploitation of the oil palm in
Orile-Owu within the purview of this broader research in this
region. In this paper, the occurrence of charred palm kernel
seeds and high percentages of oil palm pollen in association
with potsherd materials, indicative of human occupation,
are interpreted to suggest the exploitation of the oil palm by
humans in Orile-Owu.
Environmental Setting
Orile-Owu is situated in the Ayedaade Local Government
Area of Osun state, southwestern Nigeria (Figure 1), West
Africa (Figure 2). It lies within the geographical coordinates
of latitude 7°14' and 7°16'N and longitude 4°18' and 4°22'
E. This region is bounded in the south by Ijebu-Igbo in
Figure 1. Map of West Africa showing Nigeria (adapted from Dada et al
2006).
Ogun state; in the east by Ife South Local Government Area;
in the north by Gbongan and in the west by Isokan Local
Government Area (Ogundele and Ebonine 2010). Orile-
Owu experiences typical tropical temperature, vegetation
and rainfall patterns. The mean annual temperature is about
26.6°C, while the average rainfall is 1,414 mm per annum
with double maxima in June and September (Climate Data
2015). The climatic conditions at Orile-Owu presents a
suitable environment for the growth of the oil palm because
it requires best mean temperature range of 24-28°C (Corley
and Tinker 2003) and annual rainfall not exceeding 4,000
mm per annum coupled with a dry season duration not
spanning more than ve months (Goh 2000 cited in Corley
and Tinker 2003).
The physiognomy of the present-day forest vegetation in
Orile-Owu is typical of secondary forest. This is clearly
reected in the composition of the vegetation of the area with
particular reference to: (i) agricultural activities characterised
by farmlands and fallow lands, (ii) abundance of oil palm
(Elaeis guineensis Jacq.) known to thrive in open forest, and (iii)
the occurrence of forest regrowth and plants characteristic
Figure 2. Map of the study area showing location of the excavated pit (adapted
from Federal Survey, Nigeria 1966 with modications by author).
15
Original Research Paper
Kingsley Chinedu, Humans and oil palm (Elaeis guineensis Jacq.) exploitation in Orile-Owu, southwest Nigeria | Dig It 3: 14-23, April 2016
of secondary forest (Sowunmi 1987). The oil palm does
not naturally grow in the primary forest or the southern
Guinea savanna but it blossoms in areas where the climate
is favourable and there was human farming activity (Corley
and Tinker 2003). The oil palm is abundant near inhabited
areas, in tilled lands and in river valleys (Hutchinson and
Dalziel 1968). Considering its heliophytic nature, the oil
palm is ‘shade intolerant’ Sowunmi (1985:127), making it
thrive in forests where the canopy has been disturbed by
human or natural factors. Openings in the canopy permit
easy penetration of sunlight to the ground level. At Orile-
Owu, increasing present-day human activities in the form of
lumbering and farming, that usually necessitate forest clearing
and bush burning, have led to the opening of the forest
thereby creating conditions favourable for the oil palm to
ourish, further dwindling of the secondary forest.
Field observations of the present-day vegetation cover of
Orile-Owu ranging from Apomu, located in the north of
Orile-Owu to areas in the south reveal patches of dense
rainforest vegetation separated by abrupt boundaries.
These boundaries are characterised by open spaces with
buildings and scanty vegetation, and a mixture of farmland
and woody plants typical of abandoned farmlands. The
main components of the secondary forest include plants
characteristic of forest regrowth such as African border tree
(Newbouldia laevis), alum plant (Cnetis ferruginea), West African
albizia (Albizia zygia); and plant species which are known
to be well established in secondary forest such as mango
(Mangifera indica), Christmas bush (Alchornea cordifolia) and the
oil palm (Elaeis guineensis). In addition, some trees and shrubs
similar to those described by Keay (1959) belonging to the
drier northern part of the lowland rainforest zone occur
in the study area. These trees and shrubs include: g (Ficus
exasperata), African teak (Milicia excelsa), obeche (Triplochiton
scleroxylon) and kola (Cola gigantea). Also noted in the area are
climbers such as ame creeper (Combretum) and ame thorn
(Acacia ataxacantha) which grow alongside the secondary
growth and which become intertwined in the crowns of the
trees (Keay 1959). Weeds common in the area include goat
weed (Ageratum conyzoides), waterleaf (Talinum triangulare) which
is a naturalised weed which is sometimes also cultivated,
amaranth (Amaranthus), haemorrhage plant (Aspilia africana),
siam weed (Chromolaena odorata), white mouth day ower
(Commelina erecta) and beggar’s-tick (Bidens pilosa) (Keay 1959).
Farmlands, which dot the landscape, consist of cultivated
plants such as plantain (Musa paradisiaca), banana (Musa
sapientum), African star apple (Chrysophyllum albidum), sweet
orange (Citrus sinensis), maize (Zea mays), yam (Dioscorea), chili
pepper (Capsicum frutescens), kola (Cola gigantea) and cocoyam
(Colocasia esculenta). Cultivated lands are characterised by
trees, some of which may have been intentionally planted or
protected by the farmers because of their economic value.
Such trees include oil palm (Elaeis guineensis), cocoa (Theobroma
cacao), kapok tree (Ceiba pentandra), mango (Mangifera indica),
African teak (Milicia excelsa) and kola (Cola gigantea).
Materials and methods
The archaeological investigations entailed reconnaissance and
excavation. In addition, pollen analysis was carried out on soil
samples from the stratigraphic column of the excavated pit.
Reconnaissance
The study area was surveyed in 2012 and revisited in 2013
and 2014. During the reconnaissance, local inhabitants of
Orile-Owu were interviewed to gain a better understanding
of their socio-economic life with emphasis on the various
patterns of exploitation of the oil palm, their cultural histories
and the cultural landscape of the study area. Results revealed
a suitable point for excavation situated in an abandoned
settlement area, An Isale, in Orile-Owu. Oil palm, kola
and cocoa are three major cash crops as identied with the
people of Orile-Owu. These crops constitute major sources
of livelihood to the farmers as well as consumers. Palm oil
production centres are usually dominated by women with few
Figure 3. Summarised schematic drawing showing oil palm processing.
Figure 4. Local palm oil production industry (photograph by author
March 2013).
16
Original Research Paper
Figure 5. Palm oil extraction pit (photograph by author May, 2014).
Figure 7. Drying of husked mesocarp on wall of mud building (photograph by
author May 2014).
Figure 6. Palm kernel seeds surrounded by husked mesocarp (Ògùso) (photograph
by author March, 2013).
or no men. This is because the males are mostly associated
with harvesting and processing of the cocoa (Ayo Adejobi
pers. comm. 2015). Figures 3 to 7 show the space and process
of palm oil production and some of the by-products after
palm oil extraction.
Archaeological Excavation
Excavation at Orile-Owu was carried out between the
3rd and 14th of March 2013 at An Isale, an abandoned
settlement site located south of the new palace of the Olowu
of Orile-Owu. This site was selected for excavation because
it is relatively well preserved compared to other areas in
Orile-Owu and it has a long history of human occupation
since the last millenium. As revealed by our respondent,
Prince Ayo Adejobi, An Isale was initially inhabited by some
of the people of Owu before the war. The outbreak of the
war in the second decade of the nineteenth century led to the
subsequent abandonment of the area. However, Orile-Owu
was later re-occupied in the early part of the second decade
of the twentieth century (Ololajulo 2012). An Isale has no
recent human occupation except for a cocoa plantation which
is situated on the site which otherwise causes little disturbance
to the mounds. The cultural landscape is dotted by collapsed
mud buildings which have consolidated over the years to form
mounds. Some of the mounds had rodent burrows indicating
disturbance, whilst the mound selected for excavation has no
signs of disturbance, and was the highest of all the mounds in
the area with a height of 95 cm above the ground level.
After gridding the site at ve metre intervals, the mound to
be excavated was situated within the grid 15S 25E, 15S 20E
and 10S 20E, 10S 20E. A two metre by one metre test pit was
marked out and excavation proceeded at 10 cm spit intervals.
The test pit was named ‘ORILE-OWU 2013 TP1’. All the
excavated earth was sieved in a six millimetre mesh sieve and
the archaeological materials recovered were recorded, bagged,
and labelled accordingly. At completion of the excavation,
eight spit levels were established to a depth of 80 cm.
Although level 60-70 cm marked the end of the occupation
layer, a further 10 cm was dug (70-80 cm) to conrm that
the sterile layer had been reached. Based on the soil colour,
which was determined with the aid of the Munsell soil colour
chart and soil texture, three natural stratigraphic layers of the
excavated test pit were delineated (Figure 8).
Layer 1 (0-20 cm): This layer is 20 cm below the datum point.
It is dark brown in colour (7YR 3/4), composed of a loose
soil with rootlets, lithic materials (non-tools) and potsherds.
This layer is also characterised by the presence of whole palm
kernel seeds; whole palm kernels were not recovered again
from levels below this layer of the excavated unit. This is a
pointer to the present-day exploitation of the oil palm.
Layer 2 (20-54 cm): This layer lies between 20 cm and 54 cm
below the datum. It is moderately compact with dark reddish
brown colour (2.5YR 3/4). This layer has lithic (non-tools),
charcoal and the wall is characterised by lots of protruding
17
Figure 8. Stratigraphy of Orile-Owu 2013 TP1 excavated unit.
rootlets. The greatest average thickness of approximately 34
cm was recorded for this layer; this layer produced the highest
quantity of archaeological materials comprising bones,
charcoal lumps, lithic materials (non-tools), a sandstone bead
and potsherds. The occurrence of these materials indicate
that this was an occupation layer (cf. Stahl 1985). This layer
showed intense burning activities as evidenced by the high
quantity of charcoal that was retrieved.
Layer 3 (54-80 cm): This layer is characterised by a
very compact reddish soil (10YR 4/8) with thickness of
approximately 26 cm lying between 54 cm and 80 cm below
the datum. There was a drastic reduction in quantity of
archaeological materials from this layer which comprised
mainly potsherds, burnt palm kernel shell, lithic materials,
charcoal lumps, indeterminate broken tooth and bones.
Pollen analysis
Pollen analysis and microscopic charcoal particles study
were carried out on seven soil samples: from levels 72-68 cm,
52-48 cm, 42-38 cm, 26-24 cm, 12-8 cm, 6-4 cm and 2-0 cm
of the stratigraphic column, exposed vertical section of the
excavated pit at An Isale in Orile-Owu. These samples were
collected from the three established layers. This pattern of
sample collection was chosen in order to have a representation
of the entire stratigraphy. The objective of the pollen analysis
was to provide insights into human-environment interactions
in the area. Five grams of each sample was subjected to
standard pollen analysis procedure (Faegri and Iversen 1989).
Ten microlitres of well agitated mixture of palynomorphs
residue in 100% glycerine was micropipetted onto each of
six microscope slides. Microscopic study of the slides was
done with a Fisher scientic microscope and palynomorphs
were studied at x100 and x400 magnications. Identication
of the palynomorphs was established by comparison with
over 3,600 reference pollen samples at the Palynology Unit,
Department of Archaeology and Anthropology, University
of Ibadan. Unpublished photomicrograph albums at this
laboratory and published literatures such as A.P.L.F (1974),
Salard-cheboldae (1980-1987), Salard-cheboldae and
Locquin (1980) and Van Geel (2011) were also consulted.
The phytoecology of the identied palynomorphs were
determined by reference to literatures (Hutchinson and
Dalziel 1954-1972). The total number of palynomorphs
counted per subsample ranged between 2 (52-48 cm) and 450
(2-0 cm), while charcoal particles ranged between 744 (72-68
cm) and 4568 (12-8 cm) particles per gram of sediment. All
palynomorphs encountered during counting were recorded
and constituted the pollen sum with the exception of the
unidentiable palynomorphs whose features could not be
clearly distinguished due to corrosion. Additionally, certain
palynomorphs were excluded from the pollen sum at levels
where they were over-represented. Fungal spores were
excluded from the pollen sum at levels 72-68 cm, 42-38 cm,
12-8 cm and 6-4 cm, while at 2-0 cm Elaeis guineensis and
fungal spores were excluded. All excluded palynomorphs were
calculated as a percentage of the pollen sum. Considering
the low amount of palynomorphs recovered from the levels
studied, it was expedient to present the palynomorph count in
a tabular form in place of the usual pollen diagram (Orijemie
et al. 2010).
Results
Archaeology
The materials excavated were classied into two major
categories (a) organic materials: palm kernel, animal bone,
charcoal and indeterminate broken tooth; and (b) inorganic
materials further sub-divided into four categories. These
categories include: (i) pottery: body and rim sherds; (ii) lithic
materials (non-tool): granite, quartzite and goethite; (iii)
18
Kingsley Chinedu, Humans and oil palm (Elaeis guineensis Jacq.) exploitation in Orile-Owu, southwest Nigeria | Dig It 3: 14-23, April 2016
ornamental material: sandstone bead; and (iv) metal ware:
rusted knife. As in most archaeological sites in southwestern
Nigeria, pottery constituted the most common material
that was recovered. After classication, the materials in
the dierent groups were counted and their percentage
representation were calculated (Table 1). The seeds of oil
palm occurred in the topmost 10 cm of the excavated unit
and was absent throughout the stratigraphic sequence until
layer 60-70 cm where charred palm kernel endocarps were
retrieved. The reason for the absence of the oil palm seeds at
levels 10-60 cm is unclear. This may be due to the sparseness
with which the kernels were deposited or perhaps quick
deposition of the layers considering the fact that the mound
is the product of a collapsed mud building. The presence
of other materials at those layers (10-60 cm), especially the
potsherds, may be a product of the inclusion of potsherds
in the brick used in the construction of the mud building.
At present, potsherds are noticed protruding from the walls
of standing mud buildings in the area. However, further
investigation is required to get a better explanation. The
charred kernels at the bottom layer reects burning activity.
Palynology
A total of 22 pollen and spore taxa were recognised (Table
2). Of this number, 17 were pollen grains while the other
ve were spores (fungal and fern). Twelve pollen types
were identied out of the 17 pollen grains: ve of them to
the species level, three to the genus level and four to the
family level. The remaining ve pollen types could not be
Level
(cm)
Pottery Palm
kernel
seed
Burnt
palm
kernel
shell
Charcoal Tooth Bone Lithic Bead Rusted
knife
Total
Bs Rs x yz
Surface 39 4 27 - - - - - - - - 1 71
0-10 197 23 7 - - - - - 37 8 - - 272
10-20 145 15 - - † - - 2 11 1 - - 174
20-30 183 25 - - † - - 1 24 3 - - 236
30-40 137 7 - - † - 17 - 24 5 - - 190
40-50 114 17 - - † - - - 27 4 1 - 163
50-60 261 23 - - † 1 8 - 24 4 - - 321
60-70 34 3 - 3 - - - 13 - - - 53
Total 1110 117 3 160 25
1227 34 3 1 25 188 1 1 1480
Table 1. Inventory of nds - Orile-Owu 2013 Test Pit 1.
(Key: Bs = Body sherd; Rs = Rim sherd; x = Granite; y = Quartzite; z = Goethite; † = Present)
classied and so were termed unidentied. Three of the
ve spore types were fungal spores identied to the species
(Psiammopomopiospora naviculoides and cf. Lasiodiplodia theobromae)
and genus level (Brachydesmiella sp.). The fern spores were of
the mono- and trilete (Pteris sp.) types.
Discussion and Conclusion
Archaeology
In Orile-Owu situated in Central Yorubaland, farming is a
major aspect of the people’s culture. Farming in this area is
usually complemented with hunting and it is noteworthy that
the Orile-Owu farmers are also hunters. The farmers engage
in intense farming during the wet season but hunt during the
dry season. This strategy can be attributed to the availability
of water for farming. Inadequate water supply during the dry
season discourages intensive farming, while the burning of the
vegetation associated with this period makes hunting fruitful.
The plants cultivated by the farmers are cocoyam, yam,
maize, cashew, pawpaw and African star apple. Others
include banana, plantain, vegetables such as pepper, and tree
crops such as cocoa, oil palm, mango and kolanut; and the
shrub, sweet orange. Amongst all the plants in the area, the
oil palm is the most abundant. A consequence of its economic
signicance is that it is often protected, particularly during
forest clearance, an action that encourages its proliferation.
In addition, farmers do not systematically cultivate the seeds
19
Original Research Paper
Palynomorphs /Depth 72-68 cm 52-48 cm 42-38 cm 26-24 cm 12-8 cm 6-4 cm 2-0 cm
Alchornea sp 0 0.0 0.0 0.0 0.0 0.0 16.7
Alstonia boonei 00.0 0.0 0.0 0.0 0.0 2.1
Amaranthaceae 15.6 50.0 0.0 0.0 0.0 0.0 2.1
Asteraceae 3.1 0.0 0.0 0.0 0.0 9.1 2.1
Azadiractha indica 0.0 0.0 0.0 0.0 0.0 0.0 2.1
Celtis sp. 0.0 0.0 0.0 0.0 0.0 0.0 2.1
Elaeis guineensis 68.8 0.0 25.0 37.7 27.3 50.0 [44.0]
Ixora brachypoda 6.3 0.0 0.0 0.0 0.0 0.0 0.0
Lophira sp 0.0 0.0 0.0 0.0 0.0 0.0 2.1
Mimosaceae 0.0 0.0 0.0 0.0 0.0 0.0 4.2
Poaceae 0.0 0.0 0.0 0.0 0.0 9.1 0.0
Terminalia superba 3.1 0.0 0.0 0.0 0.0 0.0 0.0
Monolete ferns 0.0 0.0 0.0 2.2 18.2 13.6 37.5
Trilete ferns 0.0 50.0 75.0 2.2 54.3 13.6 22.9
Unidentiable 12.5 0.0 0.0 2.2 0.0 31.8 29.1
Unidentied 3.1 0.0 0.0 0.0 0.0 4.5 6.3
Fungal spores [63.6] 0.0 [91.4] 57.7 [77.6] [70.3] [45.0]
Charcoal 744 1086 1080 1239 4568 2514 3644
Total pollen sum (in
60µl)
32[88]224 [47]245 11[49]² 22[74]² 48[436]³
Absolute pollen count
(per gram of subsample)
213[587]² 13 27[313]² 300 73[327]² 147[493]² 320[2907]³
Table 2. Representation of Orile-Owu palynomorphs as percentage of the pollen sum.
[ ]2 = inclusion of fungal spores to the pollen sum, [ ]3 = inclusion of fungal spores and Elaeis guineensis to the pollen sum.
of the oil palm but spread them randomly. This method
of cultivating the oil palm in Orile-Owu may be another
contributory factor to its abundance in the area.
The oil palm has been used for a variety of commercial
and domestic purposes in Orile-Owu as noted during the
reconnaissance study. The reddish orange palm oil from the
mesocarp serves as cooking oil and can also be a complement
to yam, one of the staple foods in the area. More so, it is used,
in addition to yams and kolanuts, for rituals and divination
during traditional worship of Ogun-Ija (god of war), a festival
which occurs on the rst day of October every year. Other
products from the oil palm fruit include palm wine (alcoholic
beverage), edible palm kernel nut and the husked mesocarp,
locally referred to as Ògùṣọ in Yoruba parlance, is dried on the
walls of mud buildings to be later removed and used as fuel
for cooking.
As noted by Sowunmi (1999), the occurrence of the oil palm
fruit in abundance in archaeological deposits in west and
west central Africa indicates its importance in the regional
subsistence economy. The palynological study of a core
from the Niger Delta Region of Nigeria revealed that the oil
palm was a negligible constituent of Nigeria’s vegetation and
possibly the whole of West Africa before 2,800 BP after which
it became abundant, evidenced by a sudden and notable
increase in its pollen (Sowunmi 1985). High percentage
occurrence of the oil palm pollen in recent sediments has
been explained by Zeven (1964) as reecting the cultivation
of the oil palm and adoption of methods of land use suitable
for its spread. This is corroborated by the large percentage
of Elaeis guineensis pollen at a depth of 1.5 m, which was
interpreted to denote human cultivation around Bosumtwi
in Ghana about 3500–3000 BP (Talbot et al. 1984). An
increase in the fragmented woody endocarp of the oil palm
was also noted in layer 3 at K 6 rock shelter in Ghana dating
to 3550± 127 YBP (Stahl 1985). The earliest evidence for the
exploitation of the oil palm was documented at Bosumpra
cave; it was associated with a single date of 5303±100 BP
(Stahl 1993).
At Orile-Owu, although the materials retrieved from the
excavation were sparse in variety, they are meaningful
in providing insights into human occupation and the
relationships of the people with their immediate environment.
The stratigraphy of the excavation was delineated into three
20
Kingsley Chinedu, Humans and oil palm (Elaeis guineensis Jacq.) exploitation in Orile-Owu, southwest Nigeria | Dig It 3: 14-23, April 2016
Palynomorphs /Depth 72-68 cm 52-48 cm 42-38 cm 26-24 cm 12-8 cm 6-4 cm 2-0 cm
Alchornea sp 0 0.0 0.0 0.0 0.0 0.0 16.7
Alstonia boonei 00.0 0.0 0.0 0.0 0.0 2.1
Amaranthaceae 15.6 50.0 0.0 0.0 0.0 0.0 2.1
Asteraceae 3.1 0.0 0.0 0.0 0.0 9.1 2.1
Azadiractha indica 0.0 0.0 0.0 0.0 0.0 0.0 2.1
Celtis sp. 0.0 0.0 0.0 0.0 0.0 0.0 2.1
Elaeis guineensis 68.8 0.0 25.0 37.7 27.3 50.0 [44.0]
Ixora brachypoda 6.3 0.0 0.0 0.0 0.0 0.0 0.0
Lophira sp 0.0 0.0 0.0 0.0 0.0 0.0 2.1
Mimosaceae 0.0 0.0 0.0 0.0 0.0 0.0 4.2
Poaceae 0.0 0.0 0.0 0.0 0.0 9.1 0.0
Terminalia superba 3.1 0.0 0.0 0.0 0.0 0.0 0.0
Monolete ferns 0.0 0.0 0.0 2.2 18.2 13.6 37.5
Trilete ferns 0.0 50.0 75.0 2.2 54.3 13.6 22.9
Unidentiable 12.5 0.0 0.0 2.2 0.0 31.8 29.1
Unidentied 3.1 0.0 0.0 0.0 0.0 4.5 6.3
Fungal spores [63.6] 0.0 [91.4] 57.7 [77.6] [70.3] [45.0]
Charcoal 744 1086 1080 1239 4568 2514 3644
Total pollen sum (in
60µl)
32[88]224 [47]245 11[49]² 22[74]² 48[436]³
Absolute pollen count
(per gram of subsample)
213[587]² 13 27[313]² 300 73[327]² 147[493]² 320[2907]³
layers. Layer 3 (54-80 cm) constituted the lowest number of
cultural materials, an indication perhaps of the beginning of
the site’s occupation. Sediment from this layer was compact
and showed signs of good drainage and aeration as reected
in its reddish colour (Hassan 1978). Layer 2 (20-54 cm) was
also well drained and aerated, and had the highest number of
nds, a probable reection of increased human activity in the
area and a more settled lifestyle. The loose topmost layer 1 (0-
20 cm) was dark brown in colour indicating a high content of
organic matter (Hassan 1978). A reduction in potsherds was
recorded at this layer.
Furthermore, the topmost 10 cm of the excavated unit at
Orile-Owu was composed of whole palm kernels which
were not encountered again in levels below this layer in the
stratigraphic column. The seeds are the result of recent
deposition by farmers who pass through this area en route
to their farms, a pointer to present-day exploitation of the
oil palm. However, at level 60-70 cm a meagre quantity of
charred palm kernel endocarps were retrieved and produced
a date of 350±30 BP (ca AD 1450-1640; Beta-403755). The
charred endocarps occurred in association with potsherds and
charcoal which are suggestive of the fact that the oil palm was
exploited by a people who also engaged in burning activities
probably related to the clearing of land for planting but not
necessarily the oil palm. A similar interpretation was given
by scholars (e.g Alabi 2000, 2002; Orijemie 2013; Oyelaran
1991, 1998) who conducted archaeological research in
southwestern and northcentral Nigeria.
At Badagry situated in the coastal region of southwestern
Nigeria, the presence of charred palm kernels, charcoal and a
groundstone axe in the cultural phase of the Apa site 1 (AP1)
was interpreted by Alabi (2000, 2002) to indicate the possible
exploitation of the oil palm, and the clearing and burning
of vegetation preparatory to farming at 2,670 ± 90 YBP.
Similarly, Orijemie (2013) recovered charred palm kernels in
association with charcoal particles from level 130-140 cm of
test pit 1 (TP1) at Ahanve also located in the Badagry area of
southwestern Nigeria which dated to 360 ± 40 YBP (ca AD
1440-1640). According to Orijemie (2013:273) ‘the nature in
which the palm fruits were recovered indicates that they were
exploited for food and oil’. Other nds collected from 130-
140 cm at Ahanve include pottery, animal bones, sh bones,
snail shell and iron slag. Moreover, at Itaakpa in northcentral
Nigeria, Oyelaran (1991, 1998) examined burnt kernels of the
oil palm, which occurred in the basal layer (110-120 cm) and
their close association with stone axes, human remains and
ceramics. He attributed the presence of these burnt kernels to
the exploitation of the oil palm as a food source by humans as
far back as 2210 BP ± 80 YBP. Common to Apa and Itaakpa
sites are levels containing pottery, and ground and polished
stone tools with or without microliths. As highlighted by
Andah (1993:250), the pattern of occurrence of the artefact
assemblage is a possible representation of ‘denitive techno-
economic tradition’. Although at Orile-Owu and Ahanve no
lithic tools were recovered from the deposit, the occurrence
of charred oil palm endocarps and charcoal is a hint on the
presence of adopted techniques suitable for the cultivation of
the oil palm.
Palynology
Generally, pollen preservation was poor in most of the
analysed layers. This could be as a result of the sparseness
with which the palynomorphs accumulated (Sowunmi 1991)
or post depositional destruction arising from oxidation. The
lowest layer studied (72-68 cm) displayed the lowest value
of microcharcoal particles (744). The low representation of
charcoal particles at this level suggests relatively low burning
activity. Elaeis guineensis which constituted 68.8% of the pollen
sum was the highest pollen type represented at the lowest
layer. The high occurrence of E. guineensis was accompanied
by a paucity of the pollen of the rain forest species, Terminalia
superba (3.1%). Weeds were represented by the pollen of
Asteraceae and Amaranthaceae. Asteraceae was poorly
represented at the lowest layer (3.1%) coupled with a higher
value of Amaranthaceae (15.6%), which dominates in areas
highly disturbed by human activities (Daraojimba et al. 2015).
The presence of the pollen of Ixora brachypoda (6.3%), a shrub
found in swamps and moist environments, is an indication
of humid conditions (Hutchinson and Dalziel 1963). Fungal
spores were well-represented (63.6%) with Psiammopomopiospora
naviculoides, whose ecological signicance at present is not
clearly dened, contributing 1.8% to the total number of
fungal spores counted. In the next level studied (52-48 cm),
pollen preservation was very poor. Human disturbance was
evident with the presence of the pollen of Amaranthaceae
(50%). Humid conditions were indicated for this level due
to the presence of trilete ferns which are considered here
to have originated mostly from the fresh-water swamp and
rain forests (Sowunmi 1981). There was an increase in
microcharcoal particles (1086) but fungal spores, forest species
and E. guineensis were totally absent at this level. Subsequently,
E. guineensis reappeared at level 42-38 cm with a lower value
constituting 25.0% of the pollen sum. There was a further
increase in the occurrence of trilete ferns (75.0%) indicating
humid conditions coupled with a peak in fungal spores
(91.4%) and a slight decrease in charcoal (1080).
At level 26-24 cm, there was a substantial upsurge of the
pollen of E. guineensis (37.7%) associated with a decrease in
trilete ferns (2.2%) and the rst appearance of the monolete
ferns (2.2%). Fungal spores at this level decreased (57.7%) and
a further increase was noted for charcoal particles (1,239),
a possible reection of increased burning activities. The
ascomycete fungal spore, cf. Lasiodiplodia theobromae, a fungal
pathogen of woody plants was identied at this level (Slippers
and Wingeld 2007). cf. Lasiodiplodia theobromae causes die-
back and wood discoloration in their host plants in various
parts of the tropics (Slippers and Wingeld 2007). Lasiodiplodia
theobromae contributed 3.8% to the total number of fungal
spores counted at level 26-24 cm. Furthermore, noted at level
12-8 cm was a decline in E. guineensis (27.3%) linked with a
further increase in mono- and trilete ferns, 18.2% and 54.3%,
21
Original Research Paper
respectively and an increase in fungal spores (77.6%). Also,
there was an increase in the composition of cf. Lasiodiplodia
theobromae (5.3%) amongst the total fungal spores counted,
a possible indication of fungus disease infestation of the
host plants. Charcoal reached its peak level of occurrence
(4,568) at this layer. Level 6-4 cm was characterised by the
reappearance of weeds represented by an increase in the
pollen of Asteraceae (9.1%) which last appeared at the lowest
level. Grass represented by the pollen of Poaceae (9.1%)
occurred at this level for the rst time and was associated with
a concomitant rise in the pollen of E. guineensis (50.0%). The
pattern of occurrence of Asteraceae, Poaceae and E. guineensis
at this level, suggests an open vegetation and dry conditions
supported by the decline in the occurrence of mono- and
trilete ferns (13.6% each). Fungal spores and charcoal show a
reduction in frequencies compared to the previous level with
values of 70.3% and 2514, respectively. However, there was
an increase in the composition of cf. Lasiodiplodia theobromae
(7.7%) amongst the fungal spores counted, a reection of
the occurrence of fungus disease infestation. The opened
vegetation suggested at level 6-4 cm was conrmed at the
topmost level (2-0 cm) by the low percentages of the pollen
of rain forest species such as Alstonia boonei (2.1%) and Celtis
sp (2.1%), pollen of weeds and herbs associated with human
disturbance such as Asteraceae (2.1%) and Amaranthaceae
(2.1%), respectively and the occurrence of the pollen of
secondary forest species characterised by Alchornea sp (16.7%)
and E. guineensis (44%). The open vegetation which enhances
the oil palm (E. guineensis) to thrive due to its heliophytic
nature, initiated the over representation of E. guineensis at the
topmost level.
The high occurrence of charcoal particles (3,644) at topmost
level attests to increased burning activities which may have
encouraged the proliferation of the oil palm. There was an
increase in the diversity of palynomorphs recorded at this
level unlike the previous levels studied. Trace amounts of the
pollen of exotic neem tree, Azadiractha indica (2.1%) occurred
with those of guinea savanna species such as Lophira sp (2.1%)
and Mimosaceae (4.2%). An increase in mono- and trilete
fern spores, 37.5% and 22.9%, respectively was observed at
this level. Fungal spores (45.0%) further declined although
there was an increase in the percentage of cf. Lasiodiplodia
theobromae (16.8%) of the total fungal spores counted. The
presence of cf. Lasiodiplodia theobromae suggests the occurrence
of plants with the fungus disease caused by cf. Lasiodiplodia
theobromae. Other fungal spore types identied at this level
include Brachydesmiella sp. and Psiammopomopiospora naviculoides
constituting only 1.0% and 0.5%, respectively of the total
number of fungal spores. The appearance of Brachydesmiella
at this level indicate the presence of decaying wood (Sivichai
et al. 1998).
It is of interest to note that there is a contrast in the pattern
of occurrence of the pollen of E. guineensis in the pre-late
Holocene and late Holocene sediments (Sowunmi 1999). As
highlighted by Zeven (1964), the occurrence of the pollen
grains of E. guineensis in Miocene sediments was in low
frequency of about 0.1% of the pollen sum; whereas in recent
sediments, the frequency occasionally reaches 10% of the
pollen sum and can be as high as 30% of the total. This is
exemplied in the surface sample from the Niger delta where
E. guineensis reached 38.7% of the pollen sum (Sowunmi
1999). This high percentage representation of the pollen of
E. guineensis in recent sediments, in line with Zeven’s (1964)
interpretation, is a reection of the creation of conditions
favourable for the oil palm to blossom. Correspondingly,
samples from Orile-Owu exhibited the same pattern of high
occurrence of E. guineensis. However, it cannot be concretely
concluded that the oil palm was cultivated based on the
botanical data presented here but we can be certain that
conditions were created which caused the oil palm to blossom,
hence the proliferation of its pollen.
In conclusion, radiocarbon date obtained for Orile-Owu
places human occupation of it within the mid-fteenth to
the early seventeenth century. Available archaeo-botanical
evidence (although sparse) from Orile-Owu has shown that
the oil palm has been exploited by the people of the area
in the last 500 years. In all the layers studied, E. guineensis
occurred in percentages ≥ 25% of the pollen sum except
for level 52-48 cm where it was absent. E. guineensis had its
peak occurrences at the bottom (72-68 cm) and topmost (2-0
cm) levels, occurring at 68.8% and 44%, respectively of the
pollen sum. These high occurrences of the oil palm pollen
are pointers to the possible exploitation of the oil palm.
Analogously, charcoal counts from Orile-Owu sediments
provide additional stimulating results, rising remarkably from
744 at the bottom layer (72-68 cm) through 1080 (42-30
cm) and peaking at 4568 (12-8 cm) and 3644 (2-0 cm). The
upsurge in charcoal is suspected to have resulted to a greater
extent from human-made res perhaps connected with slash-
and-burn agriculture (Orijemie and Sowunmi 2014).
Considering the fact that in the interim, this paper presents
the rst single radiocarbon date from the area, more
ethnographic and palynological investigations would be vital
for meaningful studies of early farming and farming societies
in the area (Andah 1993) and help to support the argument
presented in this paper. Such studies can also generate
hypotheses about the beginning and development of dierent
agricultural traditions known to have existed from the distant
past (Andah 1993).
22
Kingsley Chinedu, Humans and oil palm (Elaeis guineensis Jacq.) exploitation in Orile-Owu, southwest Nigeria | Dig It 3: 14-23, April 2016
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23
Original Research Paper
105
106
107
... Improved seasonality in rainfall that took place during the Late Holocene (Maley et al. 2018, Bayon et al. 2019. However, human actions may have also contributed to increasing sedimentation rates (Daraojimba 2016). In addition, lithostratigraphic observations suggest that the sediment was formed under reducing and poor drainage conditions based on the greyish and brownish colours identified for most of the units (Hassan 1978). ...
... Cissus, Lophira and Triumfetta pollen types occurred for the first time in the sediment profile, an indication of increasing colonization by forest pioneer species. The increasing activity of pioneer forest taxa in this zone is corroborated by the identification of Lophira (2.1%) and Elaeis guineensis (44%) pollen grains at the topmost (0-2cm) layer of the excavated unit (Daraojimba 2016). ...
... Also, charred palm kernels (Elaeis guineensis) from layer 70-60 cm, below surface of an excavated trench, were radiocarbon dated. Archaeological and palynological investigations on the trench, 500 m southwest from the coring site, were published inDaraojimba (2016). The samples were analysed by ...
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Vegetation history of southwestern Nigerian forest during the past ~1,416 cal yr BP (534 – 644 AD) is reconstructed based on palynological data from a core from Awerele, wetland in Orile-Owu. Six palynological zones were stablished. Zone I (195-175 cm; ~1,416 cal yr BP) was a period marked by low value of charcoal particles associated with low frequency of Elaeis guineensis pollen. In Zone II (175-135 cm), the environment experienced wet conditions depicted by high percentage mainly of Cyperaceae and fern spores. Further, the arable weeds and E. guineensis increased values, showing the higher frequency of Margaritaria discoidea pollen grains, coupled with a low charcoal amount. Zone III (135-105 cm) to Zone VI (50-0 cm) were characterised by the increase of E. guineensis and raising of charcoal particles, followed by the presence of plants exploited for food and medicinal purposes, which may indicate enlarged local landscape disturbance, probably associated with humans’ activities. Archaeological evidence suggest that humans occupied the Orile-Owu area from ~ 412 cal yr BP (AD 1,538 - 1,635). The pollen data displayed the persistence of a forest-savanna mosaic, associated with ecological perturbations, which were also noticed in other parts of sub-saharan Africa on the same period.
... Improved seasonality in rainfall that took place during the Late Holocene (Maley et al. 2018, Bayon et al. 2019. However, human actions may have also contributed to increasing sedimentation rates (Daraojimba 2016). In addition, lithostratigraphic observations suggest that the sediment was formed under reducing and poor drainage conditions based on the greyish and brownish colours identified for most of the units (Hassan 1978). ...
... Cissus, Lophira and Triumfetta pollen types occurred for the first time in the sediment profile, an indication of increasing colonization by forest pioneer species. The increasing activity of pioneer forest taxa in this zone is corroborated by the identification of Lophira (2.1%) and Elaeis guineensis (44%) pollen grains at the topmost (0-2cm) layer of the excavated unit (Daraojimba 2016). ...
... Also, charred palm kernels (Elaeis guineensis) from layer 70-60 cm, below surface of an excavated trench, were radiocarbon dated. Archaeological and palynological investigations on the trench, 500 m southwest from the coring site, were published inDaraojimba (2016). The samples were analysed by ...
Article
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Vegetation history of southwestern Nigerian forest during the past ~1,416 cal yr BP (534 - 644 AD) is reconstructed based on palynological data from a core from Awerele, wetland in Orile-Owu. Six palynological zones were stablished. Zone I (195-175 cm; ~1,416 cal yr BP) was a period marked by low value of charcoal particles associated with low frequency of Elaeis guineensis pollen. In Zone II (175-135 cm), the environment experienced wet conditions depicted by high percentage mainly of Cyperaceae and fern spores. Further, the arable weeds and E. guineensis increased values, showing the higher frequency of Margaritaria discoidea pollen grains, coupled with a low charcoal amount. Zone III (135-105 cm) to Zone VI (50-0 cm) were characterised by the increase of E. guineensis and raising of charcoal particles, followed by the presence of plants exploited for food and medicinal purposes, which may indicate enlarged local landscape disturbance, probably associated with humans’ activities. Archaeological evidence suggest that humans occupied the Orile-Owu area from ~ 412 cal yr BP (AD 1,538 - 1,635). The pollen data displayed the persistence of a forest-savanna mosaic, associated with ecological perturbations, which were also noticed in other parts of sub-saharan Africa on the same period.
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Botanical and archaeological evidence of human interaction with the environment in Motako (Nigeria) is presented. Twelve soil samples retrieved from the stratified northern wall of an excavated refuse mound were subjected to pollen analysis. 12 out of 28 pollen types identified belong to plants that may have been used for medicinal, food and ritualistic purposes. The high percentage of charcoal in the earliest level dating to the last 60 years and the subsequent increase of Elaeis guineensis indicates the occurrence of rudimentary burning techniques related to clearing land for farming, hence causing opening of the vegetation (Amaranthaceae). This forest clearance created conditions favourable for the oil palm to blossom.
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Pollen analysis of a 36 m deep core from the Niger delta was carried out with a view to obtaining direct, botanical evidence of the Late Quaternary vegetation of West Africa, particularly Nigeria and Cameroon. Radiocarbon dates were obtained for five layers in the core. Practically all the pollen was river-borne, there being no evidence of long-distance wind transport. Pollen representation seemed to decrease with increasing distance of pollen source from site. Rhizophora, the dominant component of the creek vegetation in the vicinity of the site, was over-represented all through, except for the lowest portions of the core in which the pollen spectra were dominated by fresh-water swamp forest. Variations in the pollen of Rain forest plants and fern spores and that of Northern Guinea and Sudanna savanna, respectively, were regarded as reflecting climatic changes inland. Human impact on the natural vegetation was noted, beginning from c. 2800 years BP.