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VOLUME 38 2008
Proceedings
Of thE
SEMinar fOr
arabian StUdiES
Proceedings
of the
seminar for arabian studies
Volume 38
2008
Papers from the forty-irst meeting of the
Seminar for Arabian Studies
held in London, 19-21 July 2007
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Proceedings of the Seminar for Arabian Studies 38 (2008): 25–42
introduction
The pendulum of environmental change in Arabia has
oscillated between climatic extremes throughout the
Quaternary period. The landscape is riddled with evidence
for ancient pluvials, apparent in the lacustrine sediments,
alluvial fans and gravels, palaeosols, and speleothems
(e.g. McClure 1976; Schultz & Whitney 1986; Parker
et al. 2006; Lézine et al. 2007; Fleitmann et al. 2007).
Conversely, there are numerous signals that Arabia was
subjected to extremes in aridity, most obviously manifested
in the expansive sand seas comprising the Nafud, Rub’
al-Khali, and Wahiba deserts, as well as hyperalkaline
springs (Clark & Fontes 1990) and petrogypsic soil
horizons (Rose 2006).
The earliest western explorers to penetrate the Rub’
al-Khali often described a series of small buttes standing
out in stark white or grey against the seemingly endless
wasteland of monotonous rust-coloured sand. During
his pioneering journey across the desert in 1932, St John
Philby recognized these features as small eroded lake
basins comprised of marl terraces and hardened evaporitic
crusts, noting associated freshwater shells and lithic
implements scattered around the edges (Philby 1933).
The occurrence of ancient stone tools near relict lake beds
is ubiquitous throughout South Arabia and hints at a rich
prehistoric past, one of which archaeologists have only
yet encountered the tip of the iceberg.
The aim of this paper is to present the backdrop of
South Arabian prehistory by providing an overview of
the mosaic of shifting landscapes during the Quaternary.
These data provide a useful framework for understanding
the role of the climate in patterning the ebb and low of
hominin occupation across the Arabian corridor — a
critical geographic zone that has recently been established
as a conduit bridging early human populations in Europe,
Africa, and Asia.
geography, geology, and climate
The Arabian Peninsula is bounded on the west by the Gulf
of Aqaba and the Red Sea, on the south by the Gulf of
Aden and the Arabian Sea, and on the east by the Gulf of
Oman and the Arabian Gulf. The subcontinent measures
Climate change and human origins in southern Arabia
a.g. Parker &. J.i. rose
summary
Over the past few years, prehistorians have begun to consider South Arabia with increasingly greater interest. As the corpus of
genetic data grows, scholars now realize the prominent role the “Arabian Corridor” must have played in modern human origins.
Unfortunately, Palaeolithic investigations throughout the peninsula have lagged sadly behind; at the time of writing there are only
three dated, stratiied Palaeolithic sites that fall within the Upper Pleistocene time period (Shi’bat Dihya, al-Hatab, and Jebel Faya
1). While there are meagre data to discuss the human footprint upon the landscape, we possess abundant information to describe
the land itself.
This paper is intended to synthesize and present the palaeoenvironmental record throughout the late Quaternary in South
Arabia, thereby presenting the landscape across which the earliest humans traversed during the initial expansion from their ancestral
homeland. We present the HOPE ENV database, which is a composite sum probability curve that incorporates several hundred
proxy signals used to discern ancient climatic conditions. This paper considers shifts in the terrestrial landscape morphology, as
well as reconiguration of the shorelines due to eustatic and isostatic sea levels change. We discuss how this record of environmental
change might have affected human emergence, from the irst appearance of anatomically modern Homo sapiens to the development
of complex civilization in the middle Holocene.
keywords: human origins, climate change, Arabian Peninsula, palaeoenvironment, prehistoric archaeology
26 A.G. Parker &. J.I. Rose
2100 km from north to south along the Red Sea coast, and
nearly 2000 km across at its maximum width from the
westernmost region of Yemen to the easternmost point in
Oman. The littoral is characterized by tropical and subtropical
ecosystems, while the basin-shaped interior is
dominated by alternating steppe and desert landscapes.
Three major sand seas are found in Arabia: the Rub’ al-
Khali (600,000 km2), Nafud (72,000 km2), and Wahiba
Sands (12,500 km2) (Goudie 2003).
Arabia is skirted by mountainous terrain along the
western, southern, and eastern edges of the peninsula.
The ‘Asir Highlands run along the western lank of the
Kingdom of Saudi Arabia, called the Yemen Highlands
where they extend into the Republic of Yemen. This
mountain chain reaches nearly 4000 m above sea level
in the south — the highest point on the entire peninsula;
as a result, it receives up to 1000 mm of rainfall per
annum. The coastal plain of southern Arabia is bounded
by the ДaΡramawt (in Yemen) and Nejd (in Oman)
plateaus. Extending north from the Dhofar escarpment,
sedimentary beds rise sharply to an elevation of 1000 m
above sea level, gradually levelling off northwards onto
the Nejd. The entire region is comprised of uplifted
Tertiary limestone that gradually slopes into the Rub al-
‘Khali basin. The ridge of the Dhofar escarpment marks
the watershed divide; southwards-lowing drainages are
seasonally active under present conditions, incising the
limestone cliffs at a steep grade and creating springs and
lagoons as they pool onto the coastal plain. Presently, the
northwards-lowing drainages receive almost no storm
low but, during pluvial cycles, the magnitude of the
monsoon was suficient enough to produce high-energy
luvial systems.
The tectonic plate that constitutes the Arabian
Peninsula is derived from Africa. For most of geological
history, both landmasses formed part of a pan-Afro-
Arabian continent. Then, around 30 million years ago the
Arabian plate broke off from the African Shield and began
to slide to the north-east, rotating in a counter-clockwise
direction. This event triggered a chain reaction of seismic
transformations that have had an indelible effect on the
course of palaeoenvironmental and palaeoanthropological
history. One signiicant modiication was the formation of
the Red Sea trough. This narrow, elongate depression is
more than 2000 km long and varies in width from 180 to
300 km along the main channel. The rifting of these two
plates also triggered volcanic activity along the western
edge of Arabia, producing the jagged basalt peaks of the
‘Asir-Yemen Highlands.
The genesis of Arabia’s eastern mountain range is
linked to the same tectonic movement as well. As the
Arabian plate travels toward Asia, the Indian plate is
sliding beneath it and forcing the ancient bed of the Tethys
Sea to thrust upward. Consequently, the Hajar Mountains
form the spine of south-eastern Arabia, reaching 3000 m
above sea level in north-western Oman. This relatively
long chain of mountains stretches from Ras al-Hadd in
eastern Oman to the tip of the Musandam Peninsula at the
Strait of Hormuz, a distance of over 600 km. Large, low
angle alluvial fans coalesce at the mountain front, from
which an extensive network of widis low inland from
the Hajar Mountains into the Rub’ al-Khali, the Umm as-
Samim, and the Haushi-Huqf basins.
Perhaps the most profound outcome of the African-
Arabian tectonic rifting that has affected the course of
human history is compression of the Arabian plate as it
pushes against Eurasia. This process has led to geological
subsidence throughout the eastern portion of Arabia, most
notably a shallow depression that comprises the Arabo-
Persian Gulf basin. In addition, buckling sedimentary
strata created a series of north–south folds, thereby
creating the world’s largest oil reservoirs beneath the
Arabian Shelf. Under the present arid climatic regime,
the low-lying basins of eastern Arabia are dominated by
aeolian deposition, blanketed by massive sand seas.
The Wahiba Sands are located in eastern Oman,
north-east of the Haushi-Huqf Depression. This desert
is comprised of linear dunes oriented on a north–south
axis that run parallel to one another for several hundred
kilometres. The dunes reach up to 100 m in elevation and
are separated by swales 1–3 km wide (Glennie & Singhvi
2002; Preusser, Radies & Matter 2002). The most recent
aeolian deposits in Wahiba formed during the last glacial
maximum, at which time the emerged continental shelf
provided abundant unconsolidated carbonates available
for aeolian transport (Glennie 1988; Preusser, Radies &
Matter 2002).
Encompassing nearly 600,000 km2, most of the
interior of southern Arabia is blanketed by the Rub’
al-Khali sand sea. This massive basin slopes from an
elevation of approximately 1200 m above sea level in
the west to nearly sea level in the east. The dunes of the
Rub’ al-Khali include a variety of types, resulting from
the alternating wind patterns and diverse sources of sand.
The dunes are tallest in the south-western portion of the
basin, as much as 200 m in height. Like the Wahiba, the
extant features of the Rub’ al-Khali dunes formed during
the late Pleistocene, comprised primarily of reworked
Pleistocene sediments above a bed of Pliocene alluvial
gravels (McClure 1978).
Climate change and human origins in southern Arabia 27
The peninsula is subject to two different weather
regimes (Barth & Steinkohl 2004). From the north
come Atlantic late-winter north-westerlies, which move
eastwards over the Mediterranean Sea, down the Arabian
Gulf, and eventually dissipate over the Rub’ al-Khali
desert and Musandam Peninsula, bringing cool gentle
winds and light precipitation (Parker et al. 2004). The
second weather regime consists of summer storms brought
by the south-west Indian Ocean monsoon system. From
June to September, the highlands of Yemen and Oman
receive relatively heavy rainfall as the mountainous
terrain of southern Arabia traps moisture from the
monsoon (Lézine et al. 1998; Glennie & Singhvi 2002).
Consequently, the ‘Asir and Dhofar Mountains receive
between 200–1000 mm annually; while areas closer to
sea level seldom collect more than 100–200 mm per year
(Schyfsma 1978).
flora and fauna
The environmental gradients across Arabia, the loral
varieties in adjacent territories, and the legacy of
Quaternary climate change have all had a signiicant
effect upon the distribution of plant types throughout the
subcontinent (Parker et al. 2004). In southern Arabia, the
sparse vegetation cover is grouped within the following
biotopes: coastal habitat, interior basin, ‘Asir-Yemen
Highlands, Dhofar Mountains, and Hajar Mountains.
Flora such as Cressa cretica (cressa), Nitraria retusa (salt
tree) and Juncus maritimus (sea rush) are found growing
on the marine shores and salt lats. Wild rue, mangrove,
indigo, date palms, henna, tamarinds, mistletoe, and ilb
prosper around coastal wadi banks, particularly those
along the Tihama (Red Sea) and al-Batinah (Gulf of
Oman) coasts (Miller & Thomas 1996).
In the interior, plants such as tamarisks, poplars,
acacias, and several other species of reeds, grasses,
and small shrubs are found scattered near depressions
and seasonal drainage systems that receive a limited
degree of moisture (Hugh & Mason 1946). Due to heavy
precipitation deposited by the summer monsoon, there
is a wide variety of lora in the ‘Asir-Yemen Highlands.
Wild igs, leguminous trees, tamarisks, date palms,
indigo, qat, myrrh, and a variety of lowering bushes
and herbs are found along the wadi banks, while forests
of juniper cover the mountain slopes between 2500 and
3000 m elevations (1946). Pollen samples taken from
the wooded Yemeni highlands show a predominance of
acacia, Zygophyllum (Syrian bean caper), and several
species from the family Chenopodiaceae (goosefoot)
(Lézine et al. 1998). A similar distribution of lora has
been identiied in the Dhofar Mountains and described
as rolling grasslands and dense and verdant copses and
woodlands, reminiscent rather of upland regions in the
African savannah.
Indeed, the close resemblance of South Arabian loral
varieties to that of Africa is due to the fact that many of
these taxa spread eastwards from Africa. These woodland
and grassland ecosystems belong to the Saharo-Sindian
and Saharo-Arabian phytogeographic zones (Mandaville
1985; Ghazanfar & Fisher 1998; Ghazanfar 1999). The
composition of plant communities and the morphology
of endemic species suggest a close botanical relationship
between Africa and Arabia throughout the Quaternary.
Examples of East African-derived plant types include
Acacia sp. (Acacia), Ziziphus ziziphus (Jujube), and
Apocynoideae rhazya (dogbane).
Plant types in south-eastern Arabian (the modern
territories of northern Oman and the UAE) show strong
ties to the lora of Iran and south-western Pakistan
(Baluchistan), comprising the Omano-Makranian subzone
of the Nubo-Sindian centre of endemism (Mandaville
1985; Ghazanfar & Fisher 1998; Ghazanfar 1999). Floral
elements that are linked to Asian taxa include Euphorbia
larica (succulent spurge), Prunus amygdalus (almonds),
Ficus carica (igs), Lawsonia inermis (henna), and
Indigofera tinctoria (true indigo). These pronounced
afinities in plant distribution across the Omano-
Makranian sub-zone are attributed to the fact that during
much of the Quaternary the basin of the Arabian Gulf was
exposed, forming one continuous territory from Arabia
into South Asia (Williams & Walkden 2002).
Of the large mammals, animals belonging to the
family Bovidae are by far the most prominent on the
Peninsula. These include one species of oryx, three
species of Gazella, two species of Capra, one belonging
to the genus Hemitragus (wild goat), and one of the genus
Ovis (wild sheep). These animals typically occupy areas
that receive moderate to high amounts of rainfall such as
the Yemeni highlands, Dhofar, and the Hajar Mountains.
Gazelle have been noted from more arid settings such
as the high plateaus, while the desert-adapted oryx were
once ubiquitous throughout the interior, even within the
Rub’ al-Khali (Harrison 1980).
Small mammals include various species from the
family Soricidae (shrews), order Rodentia (rodents), and
order Chiroptera (bats). There are carnivores such as
mongooses, genets, dogs, wolves, and foxes (Harrison
1980). A variety of felines are present, including Felis
silvestris (wild cat), Felis margarita (sand cat), Caracal
28 A.G. Parker &. J.I. Rose
caracal (Caracal lynx), Panthera pardus (leopard), and
Acinonyx jubatus (cheetah) (Harrison & Bates 1991).
Like the Bovidae family, these animals are typically
found in and around the montane zones. There are some
examples of Lagomorpha (rabbits, hares, and pikas)
reported from the interior — on the desert plateaus and
along the margins of the Rub’ al-Khali (1991).
Much like the pattern of loral distributions, there
are strong inter-regional links between Arabian fauna
and adjacent areas. Terrestrial snails of northern Oman
are primarily Palaearctic taxa, while snails found west
of Dhofar have East African afinities (Mordan 1980).
Fernandes et al. (2006) report mtDNA evidence for a
recent genetic divergence between African and Arabian
genets. They note several other small and medium-sized
carnivores (e.g. mongooses, desert foxes, honey badger,
caracal, jungle cat, golden jackal) that occur on both
sides of the Red Sea that may also be genetically linked.
Harrison (1980) corroborates these African and Arabian
faunal connections, observing that Crocidura somalica
(shrew) and Genetta granti (genet) are closely related to
East African varieties.
Another indicator of faunal connections across the
Red Sea is the presence of the primate Papio hamadryas
— Sacred Baboon — in Yemen. Presently, these primates
are indigenous to the rocky hill country of Somalia,
Ethiopia, and Yemen. Papio hamadryas are arid-adapted
creatures that forage protein-rich insects, hares, and other
small mammals; they obtain water from shallow pools
and by digging small wells in desert regions with a high
water table (Nowak 1991). Analyses of Papio hamadryas
mtDNA lineages on both sides of the Red Sea suggest that
they originated in East Africa sometime between 150,000
and 50,000 years ago, and subsequently migrated into
figure 1. Laminated lacustrine strata at Wahalah Lake, Ras al-Khaimah, UAE.
Climate change and human origins in southern Arabia 29
Arabia (Wildman 2000; Wildman et al. 2004; Fernandes,
Rohling & Siddell 2006). That the East African baboon
lineage is older than the Arabian implies that there must
have been a demographic bottleneck release sometime
during the Upper Pleistocene.
Pleistocene and early holocene climate
change in arabia
Most of the precipitation that falls over Arabia is brought
by the afore-mentioned south-west Indian Ocean monsoon
system, considerably more so than from “north-westerly”
winter storms. Consequently, the environmental fate of
the region, amelioration or desiccation, rests upon the
intensity of the monsoon, which has been in lux for at
least the last quarter of a million years (Clemens et al.
1991; Muzuka 2000; Fleitmann et al. 2004).
indian ocean monsoon cycles: life and death of the
south arabian landscape
Marine cores from the Indian Ocean, Gulf of Oman, and
the Arabian Sea provide a detailed history of the south-west
Indian Ocean monsoon system throughout the Quaternary.
Analysis of dinolagellate cyst content from Arabian Sea
deep sea cores during the last glaciation reveals an abrupt
luctuation at 12,500 years ago (Zonneveld et al. 1997).
This spike is attributed to the disappearance of snow and
ice cover over central Asia, Tibet, and the Himalayas,
suggesting that one of the primary mechanisms driving
monsoon luctuations are climatic conditions at glacialinterglacial
boundaries. Biogeochemical and lithogenic
data from Arabian Sea cores spanning the last 350,000
years also support the notion that monsoon winds were
sensitive to changing glacial climates. The retreat of
ice sheets, the rise in continental albedo (solar radiation
relected off the earth’s surface), and the increase of
water surface temperatures in the western Indian Ocean
triggered spikes in magnitude (Clemens et al. 1991).
Computer simulations have been used to estimate the
average wind speed of the south-west monsoon during
such phases of intensiication. Speeds currently average
around 10 m/sec, while increased periods of activity the
saw wind speeds reaching 15 m/sec. Precipitation would
have been 50 % greater than its present value, growing
from 5 mm/day to 7.5 mm/day. Northwards-shifting
insulation patterns drove the monsoons further into the
Arabian Peninsula, with evidence for seasonal storms
reaching as far north as Bubiyan Island in the Arabian
Gulf (Sarnthein 1972; Kutzbach 1981).
Researchers have attempted to model the rate of
change during shifts in monsoon magnitude. Analysis of
15N isotopes was conducted on an interval of Arabian Sea
figure 2. Relict luvial terrace in Wadi Arah, southern Oman.
30 A.G. Parker &. J.I. Rose
core spanning the bracket of time between 43,000 and
42,000 years ago — a well-established climatic boundary.
Signiicant changes in mean strength occurred within a
span of 200 years, which is relatively instantaneous on
a Pleistocene time scale (Higginson 2004). While the
onset of the intensiied monsoon was rapid, evidence has
been presented suggesting that the shift back towards
aridiication was a more gradual process occurring on a
millennial scale, at least during the most recent wet/dry
shift (Lückge et al. 2001).
The stable oxygen isotope record of various planktonic
foraminiferal species (i.e. Globigerinoides ruber,
Globigerina bulloides, and Neogloboquadrina dutertrei)
attests to temporal variations in marine palaeoproductivity.
Analysis of species frequency distribution over the last
glacial cycle shows a direct correlation between palaeoproductivity
in the Arabian Sea, the strength of the
monsoon, and the global oxygen isotope curve. Scholars
note the onset of intensiied monsoon episodes can lag up
to 1000 years after shifts in glacial conditions, possibly
due to the threshold necessary for suficient amounts of
snow and ice to melt and affect Indian Ocean insulation
patterns (Reichart, Lourens & Zachariasse 1997; Petit-
Maire et al. 1999; Ivanova et al. 2003).
Fluctuations in monsoon intensity are evidenced by a
variety of signals upon and within the landscape. The most
complete records come from a series of dated speleothems
in the Hajar and Dhofar mountains. Pronounced pluvial
conditions are also signalled by remnants of ancient lake
deposits (Fig. 1), travertines, luvial terraces (Fig. 2), and
alluvial fans spreading along the piedmont regions. The
expansive sand seas found throughout Arabia’s desert are
a testament to the hyperarid phases that have occasionally
swept across the peninsula (Fig. 3).
We have compiled all of these palaeoenvironmental
signals together to build a comprehensive database of
figure 3. Late Pleistocene dune proile at ash-Shwaib, UAE.
Climate change and human origins in southern Arabia 31
climate change in Arabia, referred to as HOPE ENV.
These data are derived from published sources as well as
new evidence collected by the authors in the ield. Based
on a total of 396 absolute dates, we present a composite
sum probability curve (Fig. 4) to illustrate climatic
oscillations over the past 175,000 years, from MIS 6 to
present. Peaks in sum probability represent periods of
increased wetness, while troughs highlight drier phases.
All dates are reported in calendar years BP.
Climatic conditions during the late Middle and Upper
Pleistocene are of particular interest to our study, given
that this span of time formed the backdrop of early human
emergence from Africa. Was the climate arid enough
during the last few glacial maxima to preclude hominin
habitation and, conversely, were conditions humid
enough to facilitate human occupation during the Last
Interglacial?
Anton (1984) speculated that the environment was
hyperarid during MIS 6, given that monsoon intensity
roughly tracks with the global marine isotope curve. The
emerging picture in Arabia indicates the situation was
more varied than this initial assessment; a smattering of
chronometric dates suggests there were brief pulses in
precipitation. Compelling evidence for increased moisture
at the MIS 7-MIS 6 interface comes from speleothems in
Hoti Cave, northern Oman, where U/Th measurements
exhibit an increase in growth rate between 200–180 ka
(Burns et al. 2001). The prospect of stage 6 sub-pluvials
are corroborated by optical dates on luvial silts at Sabkha
Matti (147,000 ± 12,000 BP) (Goodall 1995), two U/
Th measurements from freshwater mollusca within
lacustrine sediments at Mudawwara (170,000 ± 14,000
BP and 152,000 ± 8,000 BP) (Petit-Maire et al. 1999),
optically dated luvial silts at Falaj al-Moalla in the Wadi
Dhaid, UAE (193,110 ± 30,750 BP), OSL measurements
on luvial silts recorded at the Camel Pit Site, Umm
al-Qawain, UAE (174,300 ± 24,110 BP), and optical
measurements on evaporitic lacustrine sediments sampled
from a relict interdunal sabkha in the Liwa region of the
Rub’ al-Khali, UAE (160,000 ± 8000 BP) (Wood, Rizk &
Alsharhan 2003).
The onset of the Last Interglacial period around
130,000 years ago was punctuated by an abrupt and
drastic increase in rainfall over South Arabia that lasted
figure 4. HOPE ENV sum probability curve depicting wet/dry signals throughout Arabia during the Upper
Pleistocene.
32 A.G. Parker &. J.I. Rose
until approximately 120 ka, followed by a second peak in
precipitation corresponding with MIS 5a (82–74 ka). U/
Th dates on palaeosols from the western piedmont of the
Hajar Mountains in Oman that are correlated with isotopic
stages 5e and 5a (Sanlaville 1992). Soils were also noted
in the ad-Dahna Desert of northern Arabia, where late
Pleistocene dunes overlie two separate pedogenic strata
that could only have formed on stabilized dunes with
a dense cover of vegetation (Anton 1984). There is a
network of Plio-Pleistocene bas-relief gravel channels
west of the Wahiba desert that is superimposed by thinner
luviatile gravels tentatively associated with particularly
humid episodes during MIS 5e and MIS 5a (Maizels
1987). Stokes and Bray (2005) obtained over ifty optical
dates from megabarchan dunes in the Liwa region, which
lies along the eastern margin of the Rub’ al-Khali. Their
indings suggest a prolonged period of dune accumulation
from 130 to 75 ka. This deposition was attributed to a
unique combination of factors such as reduced sea levels
in the Arabo-Persian Gulf that produced an abundance
of sedimentary material available for transport, a rise in
regional groundwater levels, and vegetation cover that
stabilized the dunes. Multiple MIS 5 pluvial episodes are
signalled by the aforementioned Hoti Cave speleothems,
which yield U/Th dates indicating rapid growth between
135–120 ka and 82–78 ka. Researchers noted that
speleothem growth was most pronounced during MIS 5e,
more so than all subsequent pluvials (Burns et al. 1998;
2001). Most recently, we have dated a series of buried
alluvial fans interstratiied with luvial sands along the
western edge of the Hajar Mountains in Ras al-Khaimah,
UAE. OSL ages obtained from these sediments indicate
they were deposited at 117,030 ± 15,080 BP and 107,970
± 9660 BP.
There are meagre climatic data from MIS 4 and early
MIS 3 in southern Arabia. Indirect evidence from the
HOPE ENV summed probability curve as well as the
index of Indian Ocean Monsoon activity (Fleitmann et
al. 2007) suggests this time frame was characterized by
increasingly hyperarid conditions culminating around 70
ka, followed by a return to a more humid regime by 50,000
years ago. The only physical evidence for aridiication
during MIS 4 can be inferred from stratigraphic proiles
in the Rub’ al-Khali, which attest to a stage of aeolian
accumulation sometime before 37,000 years ago. This
deposition, however, is relatively minor as compared to
the immense aeolian structures that accumulated during
the terminal Pleistocene (McClure 1978).
Geological investigations in the heart of the Rub’ al-
Khali sand sea have revealed a landscape during MIS
3 that featured a series of small lakes spread across the
interior (McClure 1984). Radiocarbon measurements
on mollusc shells and marls indicate the lakes reached
their highest levels around 37,000 BP (McClure 1976).
These playas ranged from ephemeral puddles to pools
up to 10 m deep, and numbered well over 1000. They
are primarily distributed along an east–west axis across
the centre of the Rub’ al-Khali basin, covering a distance
of some 1200 km (McClure 1984). Similar lake basins
have been reported from the Ramlat as-Sabatayn desert
in Yemen (Lézine et al. 1998; 2007), as well as the Nafud
in northern Arabia (Garrard & Harvey 1981; Schulz &
Whitney 1986).
Researchers speculate that lake-illing episodes were
short-lived; these poorly drained basins would have
been recharged by occasional torrential stormlow runoff
and disappeared within a few years. Due to the region’s
wide catchment area, the Mundafan depression was the
exception to this model. Arabia’s thickest lacustrine
deposits were recorded here, where single lake periods
are estimated to have lasted at least 800 years. Fossilized
faunal remains excavated within the Mundafan sediments
yielded a menagerie of large vertebrates including oryx,
gazelle, aurochs, wild ass, hartebeest, water buffalo, tahr,
goat, hippopotamus, wild camel, and ostrich (McClure
1984). Most of these species belong to the family Bovidae,
whose survival required expansive grasslands produced
by light to medium rainfall distributed evenly over the
Rub’ al-Khali.
Ostracoda and freshwater mollusca indicative of low
salinity were present at Mundafan, as well as species
of foraminifera that attest to highly brackish conditions
(McClure & Swain 1974). Evidence of grasses, shrubs,
and herbs are indicated by both phytoliths and dikaka —
thin, tubular fragments of fossilized material scattered
in the aeolian sediments around the basins. These loral
fossils were formed when dissolved calcium carbonate in
the water precipitated onto plants as the lake evaporated.
Evidence of ish remains are conspicuously absent
from the Rub’ al-Khali lakes, because lakes were rarely
reilled and became too alkaline too quickly to develop a
population (McClure 1984).
In addition to interior palaeolakes, other signals for
an MIS 3 wet phase include depositional terraces in
the Wadi Dhaid; although undated, their stratigraphic
position suggests an age between 35 and 22 ka BP
(Sanlaville 1992). Interdunal sibakh recorded in the
Liwa region of the UAE have produced thirty-one dates
(both uncalibrated 14C as well as OSL) that cluster
between 46,500 and 21,500 BP (Wood & Imes 1995;
Climate change and human origins in southern Arabia 33
Juyal, Singhvi & Glennie 1998; Glennie & Singhvi
2002). Palaeosols have been recorded in the ad-Dahna
desert, which are stratigraphically positioned between
MIS 4 and MIS 2 aeolian deposits (Anton 1984). Clark
and Fontes (1990) dated calcite formations from ancient
hyperalkaline springs in northern Oman, producing
radiocarbon ages between 33 and 19 ka. Two soil horizons
were discovered around the central plateau of the Yemeni
highlands, characterized as molissols — soils that form on
landscapes covered by savannah vegetation. Uncalibrated
radiocarbon measurements were 26,150 ± 350 BP for the
lower stratum, and 19,290 ± 350 BP for the upper horizon
(Brinkmann & Ghaleb 1997).
Researchers speculate that the Terminal Pleistocene dry
phase was more arid than the peninsula had experienced
since the Penultimate Glaciation, if not earlier (Anton
1984). Ages obtained from dune formations in the Rub’
al-Khali (McClure 1984; Goudie et al. 2000; Parker &
Goudie, 2007), an-Nafud (Anton 1984), and the Wahiba
Sands (Gardner 1988; Glennie & Singhvi 2002) all
signal a major phase of aeolian accumulation between
17,000 and 9000 BP. Calcite fractures in northern Oman
corroborate the evidence for increasing aridity, indicating
there was considerably less moisture in the environment
starting around 19,000 BP (Clark 1990). The Terminal
Pleistocene hyperarid phase ended with yet another
pronounced oscillation back to humid conditions. This
pluvial phase period lasted until c. 5000 BP, at which time
the present climatic regime was established (Overstreet
& Grolier 1988; Cleuziou, Inizan & Marcolongo 1992;
Sanlaville 1992; Brunner 1997; Wilkinson 1997; Stokes
& Bray 2005; Parker et al. 2004; 2006a; 2006b; 2006c).
shifting shorelines and human refugia
As profound as these climatic oscillations have been
over the course of the Quaternary, the rise and fall of sea
level has had an even greater effect on the coniguration
of the Arabian subcontinent. Taking into account the
shallow bathymetry of the Arabo-Persian Gulf and Red
Sea basins, nearly 1 million km2 of contiguous land
have been repeatedly exposed and submerged by glacioeustatic
cycles of marine regression and transgression
(Fig. 5). The emergence of the continental shelf around
Arabia had direct implications for prehistoric occupation,
since the exposed landmass provided abundant sources of
fresh water amidst a generally desiccated landscape. The
role of littoral zones in the dispersal of modern humans is
the crux of ongoing discussion; recent models of human
emergence from Africa envision rapid coastal migration
across the southern route of dispersal, facilitated by a
new adaptation to aquatic resources (e.g. Stringer 2000;
Mithen & Reed 2002; Mellars 2006). Evidence suggesting
the importance of low-lying coastal habitats during the
early and middle Holocene has been discovered by Bailey
et al. (2007a; 2007b) around the Farasan Islands in the
southern Red Sea, who report a nearly continuous line of
over 1000 shell mounds along the beachfront.
Faure, Walter and Grant (2002) have identiied a
process of littoral freshwater upwelling they refer to as
the “coastal oasis” hypothesis that may help explain the
importance of coastal habitats for early humans groups.
Depressed sea levels during glacial maxima caused an
increase of hydraulic pressure within submarine rivers;
consequently, more freshwater lowed through these
aquifers. Eventually, this process led to the creation of
springs in favourable loci on the emerged shelf with
lithology, faults, bathymetry, and/or topography conducive
to upwelling. Such a phenomenon can be observed today
in the abundant submerged seeps at the bottom of the
Arabo-Persian Gulf. The area around modern Qatar is the
terminus of several submarine rivers that low beneath
Arabia, creating a mass of upwelling plumes once used
by ancient seafarers for restocking their freshwater stores
(Church 1996).
Indeed, a god known as Enki, the “Lord of the Sweet
Waters”, was revered by the Gulf’s earliest inhabitants
— a group which originated in the basin prior to its inal
inundation in the fourth millennium BC. Enki was believed
to dwell within the “Abzu”, the freshwater of the deep;
in the “Myth of Enki and Ninhursag” he is credited with
building canals to bring freshwater to Dilmun (Jacobsen
1987). This example taken from Sumerian mythology
serves as a useful frame of reference to highlight both
the availability and importance of freshwater within the
Arabo-Persian Gulf basin throughout the Pleistocene
and Early Holocene. The Gulf is the shallowest inland
sea in the world, averaging just 40 m in depth and
covering some 225,000 km2 (Sarnthein 1972). Therefore,
between 115,000 and 6,000 years ago, when sea levels
were depressed below current levels, we speculate that
this region served as a large refugium for local biomass
(including hominins) constricted by arid conditions (for
further discussion of the role of the Gulf basin in protohistory
see Sayce et al. 1912; Barton 1929; Cooke 1987;
Teller et al. 2000; Kennett & Kennett 2006; Sanford
2006).
Throughout the Upper Pleistocene and Early/Middle
Holocene, nearly all excess runoff in south-west Asia
was funnelled into the Gulf basin via submarine aquifers
34 A.G. Parker &. J.I. Rose
lowing beneath Arabia, the Karun drainage originating in
the Zagros Mountains, and the Tigris and Euphrates Rivers
lowing from the Anatolian Plateau. All of these drainage
systems converged within the centre of the basin, forming
the Ur-Schatt River, which once traversed the entire length
of the basin through a deeply incised canyon that is still
evident in the extant bathymetry (Seibold & Vollbrecht
1969; Sarnthein 1972; Uchupi, Swift & Ross 1999).
The most recent phase of Ur-Schatt River downcutting
culminated during the Last Glacial Maximum, when
global sea levels were reduced by 120 m and the basin
was exposed in its entirety. Sometime around 14,000
BP, the Straits of Hormuz were breached by the Gulf
of Oman, and by 12,500 BP marine incursion reached
the central basin of the Gulf. This process of inilling
has been relatively gradual; the waters only reached the
present shoreline as recently as 6000 years ago, at which
time the sea exceeded its current levels by 2 m (Bernier et
al. 1995; Lambeck 1996; Williams & Walkden 2002).
There is freshly unearthed evidence hinting at the
importance of the Gulf basin refugium throughout
prehistory. One such example is the unexpectedly early
presence of Ubaid-related (late Neolithic) sites clustering
along the southern coastline and located on islands
within the Gulf itself (Haerinck 1991; 1994; Hermansen
1993; Jasim 1996; Beech & Elders 1999; Beech, Elders
& Shepherd 2000; Beech et al. 2005; Carter 2006). The
sudden appearance of a fully-sedentary, agrarian society
within this previously uninhabited niche is incongruous
with the pace of local Neolithic development. Therefore,
we suggest the pattern of Ubaid-related settlements
in south-eastern Arabia is reason to revive the age old,
figure 5. Map of Arabia showing drainage channels and signiicant Pleistocene geomorphic features.
Climate change and human origins in southern Arabia 35
unanswered debate: “from whence came the Sumerians?”
(Barton 1929). This question becomes even more
intriguing in light of new genetic evidence obtained from
modern populations around the Gulf, who carry signature
lineages from Africa, Asia, and Europe (Reguiero et al.
2006; Shepard & Herrera 2006). Based on these indings,
Reguiero et al. (2006) describe the area as a “tricontinental
nexus” for human dissemination.
discussion: modelling demographic
response
In considering the early human drama that unfolded
amidst the backdrop of the wildly metamorphosing
Arabian landscape, it is useful to consider a passage from
Abd al-Qadir al-Jilani’s ninth-century text Kitab Sirr al-
Asrar, later translated into English by Sir Isaac Newton:
“that which is below is like that which is above” (Dobbs,
1983). A more down-to-earth rendition of this statement
might imply that demographic history in Arabia mirrors
the evolution of the landscape.
This metaphor is rooted in deep geological time, when
the Arabian tectonic plate split from Africa, forming the
Red Sea trough. Genetic studies indicate that modern
human emergence occurred in a similar manner, when a
group derived from mtDNA superhaplogroup L3 branched
from the ancestral population sometime prior to 75,000 BP
(e.g. Metspalu et al. 2004), perhaps as early as 300,000
years ago (Yotova et al. 2007). Far from a geographic
barrier, the Red Sea was a conduit for both plants and
animals throughout the Quaternary. While there was no
land bridge at any point during this phase (Siddall et al.
2002: 203–206), reduced sea levels rendered the narrow
crossing at the southern extent of the Red Sea a negligible
barrier. Moreover, the body of water lanking the eastern
margin of the Arabian subcontinent did not exist for
the majority of the Upper Pleistocene (Lambeck 1996;
Uchupi, Swift & Ross 1999); the absence of this waterway
was undoubtedly an integral part of the prehistoric plot.
Distributions of lora and fauna across eastern Arabia —
predominantly Palearctic taxa — demonstrate the region’s
natural Eurasian afinities. It is not surprising that Upper
Pleistocene lithic industries follow the same geographic
patterning (Rose 2007).
We have seen that life and death within the interior
of South Arabia was dependant upon the intensity of the
Indian Ocean monsoon. When global insulation patterns
forced the monsoon northwards, the hinterland was
transformed into a sub-tropical savannah. Conversely,
when rainfall ceased during glacial maxima, the majority
of the peninsula became a barren wasteland. Given these
extreme luctuations, in conjunction with its position at
the intersection of Africa, Asia, and Europe, it is likely
that South Arabia served a unique role in the prehistoric
world: a bridge during pluvials and a barrier during arid
phases.
It is only appropriate to envision these processes in
the sense of long term, inter-regional genetic exchange;
we do not yet possess a suitable degree of resolution
within the palaeoclimatic and archaeological records to
assess actual demographic events. Any statement about
Upper Pleistocene human migrations out of Africa and
into Arabia would be premature and grossly presumptive.
There are data suggesting that certain parts of the
Arabian subcontinent served as stable refugia during
environmental downturns. Thus, to understand the role
of the peninsula in the story of human origins, it is more
productive to consider populations tethered to refugia,
expanding and contracting from such habitats during
cycles of amelioration and desiccation.
This paper has demonstrated that Quaternary climate
change in Arabia was a complex process that produced
diverse landscapes across the peninsula. For instance,
while glacial events resulted in an entirely inhospitable
environment within the interior, portions of the emerged
continental shelf were paradisiacal gardens. Rather than
a simplistic scenario of Homo sapiens marching across
Arabia at the onset of the “human revolution”, we must
expect that prehistoric occupation was as complex and
varied as the landscapes upon which they dwelt.

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