Australia: The Land Where Time Began |
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Human Occupation of Northern India Spans the Toba Super-eruption
about 74.000 Years Ago
For understanding the dispersal of
Homo sapiens out of
Africa and into Asia and Oceania, India is located at a crucial
geographic crossroads. In this paper Clarkson et
al. report evidence for
long-term occupation by humans at the site of Dhaba in the Middle Son
River Valley of Central India that spans the last about 80,000 years. A
stone tool industry that has been unchanging was found at Dhaba that
spanned the Toba eruption of about 74 thousand years ago (ka) (i.e., the
youngest Toba Tuff (YTT) that bracketed between 79.6 ± 3.2 and 65.2 ±
3.1 ka, with the introduction of microlithic technology about 48 Ka.
There is a strong resemblance between the stone tool assemblages from
the African Middle Stone Age (MSA) and Arabia, and the earliest
artefacts from Australia, which suggests that is the likely to be the
Product of
Homo sapiens as they
dispersed to the east out of Africa.
According Clarkson et al.
India is a focus of intense debate about the timing of arrival of
Homo sapiens, the
material culture signature of occupation by modern humans, the nature of
the replacement of archaic populations, and the impact on populations of
hominins of the YTT volcanic eruption about 74 ka. For this key period
of time there is no known fossil record of hominins, analysis of DNA of
contemporary populations of India indicates that the region was an
important geographic stepping stone in the colonisation of Australasia
by
Homo sapiens (Atkinson,
Gray & Drummond, 2007). The issue of whether
H. sapiens arrived in
India before the YTT event (dated by 40Ar/36Ar to
73.88 ± 0.32 ka1 and 75 ± 0.9 ka2) (Storey,
Roberts & Saidin, 2012; Mark et
al., 2014; Rose & Chesner, 1987; Acharyya & Basu, 1993; Shane, 1995;
Westgate et al., 1998; Pearce
et al., 2014; Pearce,
Westgate et al., 2019;
Petraglia et al., 2007) with
a non-microlithic African MSA technology that was comprised of Levallois
and point technology (Petraglia et
al., 2007; Clarkson, 2014;
Groucutt, 2014), or entered the subcontinent about 50-60 Ka with
Howiesons Poort microlithic technology (Mellars et
al., 2015), is at the heart
of this debate. The reality is that though this debate is pivotal to
understanding the archaeological signature of modern humans throughout
the region, very few sites in India are dated to the crucial time period
between 80 and 50 ka, therefore reliable evidence which could be used to
test competing hypotheses is scarce. The debate over the South Asian
record is focused to a large extent on stone tools and the DNA of modern
populations, as well as rare finds such as the engraved ostrich eggshell
and worked osseous tools from a few sites (Mellars et
al., 2015), as a result of
the sparse human skeletal record from the Pleistocene between Africa and
South Asia (Dennell & Petraglia, 2012; Rabett, 2018).
In this article Clarkson et al.
report detailed descriptions of a rich collection of lithic artefacts
that have been recovered from the Dhaba locality, which is situated on
the banks of the Middle Son River in Madhya Pradesh, in northern India,
which is comprised of 3 nearby localities (Dhaba 1, 2, and 3) (Haslam et
al., 2012) as well as the
associated luminescence age estimates. A detailed archaeological
sequence is provided by the Dhaba locality for the Middle Son Valley in
a crucial time range of about 80–40 ka, and is positioned
chronologically between the early Middle Palaeolithic/Late Acheulian
sites of Patpara, Nakjhar, Khurd, Sihawal and Bamburi 1, dated to about
140 to less than 104 ka (Haslam, 2011; Shipton et
al., 2013) and the
blade-based technologies of the ‘Upper Palaeolithic’ that were recovered
from the deposits at Baghor Formation, that had previously been dated to
about 39 ka, though the latter age is problematic
(Jones & Pal, 2009; Petraglia et
al., 2012) (see Supplementary
Discussion for more detailed discussion and Supplementary Fig. 8 for
site locations). Clarkson et al.
report in this study infrared stimulated luminescence (IRSL) ages for
feldspar rich in potassium (K-feldspar) grains, which were collected
from cultural sequences, were excavated at Dhaba. In order to frame
chronological changes in lithic technology at this site and to place the
evidence within the context of the South Asian Palaeolithic and, more
broadly, the dispersal of modern humans (Field, Petraglia & Lahr, 2007),
they used the IRSL ages.
There are 3 archaeological excavations that comprise the Dhaba locality
(Dhaba 1, 2 and 3) on the northern banks of the Son River and west of
its confluence with the Rehi River. The 3 archaeological excavations are
each consisted of a step trench placed into hill slope sediments. Dhaba
1 (N 24o29’57.6”, E 82o00’35.0”) was selected as
the location that had the densest surface artefact concentration that
dated to the Middle Palaeolithic, with artefacts that were visibly
eroding from the sediment at several points up the slope. Dhaba 2 (N 24o29’55.4”,
E 82o00’24.5”) and Dhaba 3 (N 24o29’56.1”, E 82ooo’22.5”)
were selected for excavation because of the eroding accumulations of
artefacts from the Middle Palaeolithic, and a dense concentration of
cryptocrystalline microblade and small flake artefacts higher up the
slope at Dhaba 3. At Dhaba 1 and Dhaba 2 excavations are about 600 m and
about 900 m west of the Rehi-Son River confluence, respectively. The
trenches were excavated into colluvial and alluvial sediments that
overlie the Proterozoic sandstone and shale bedrock of the Vindhyan
Supergroup (Ray, Veizer & Davis, 2003; Korisettar, 2007). Substantial
deposits of YTT, that are chemically identified, are exposed about 700 m
to the east of Dhaba: at Ghogara on the northern bank of the Son River
(Jones, 2010; Gatti et al.,
2011), and on the east bank of the Rehi River (Lewis et
al., 2012; Neudorf, Roberts &
Jacobs, 2014a; Neudorf, Roberts & Jacobs, 2014b), in cliff sections.
Pedogenically altered alluvial sands, silts and clays were exposed in
the step trenches. At Dhaba 1 and Dhaba 2, the top step trenches are
about 16 m above the river level. At Dhaba 1 the trench revealed a
sequence of floodplain silts, clays and sands with angular sandstone and
shale pebbles, carbonate nodules and rhizoliths that coarsened-upwards.
Angular limestone, sandstone and shale boulders that were derived from
the underlying bedrock are overlain by these floodplain sediments. At
Dhaba 2 the trench exposes floodplain clays, silts and sands that
contain carbonate nodules and a few angular pebbles that overlie shale
bedrock. At Dhaba 3, that is about 1 km west of the Rehi-Son River
confluence, a trench that is about 3 m deep and about 21 m above the
level of the river that was dug into the southeastern facing slope of a
hill that is composed of colluvial silts, sands and gravels that overlie
sandstone and shale bedrock that is decomposing. At the top of the
hillock the estimated thickness of the colluvial sediments is about 5 m.
Silty sands and pebble gravel, with angular sandstone and shale clasts,
is exposed in the trench. South and southeast draining gullies that feed
into a channel, in turn, drains into the Son River, separate the hillock
from the neighbouring sandstone and shale bedrock ridge which rises to
the west to more than 40 m above the river level. A terrace that dates
to the Holocene that is about 10
high, that is composed of sands and silts abuts the north bank of
the Son River (Haslam et al.,
2012; Neudorf, Roberts & Jacobs, 2014b). Large, angular quartzite
boulders, that are exposed intermittently for more than 100 m along the
riverfront, is underlain by this terrace. The removal of large flakes by
the use of hard hammer percussion is visible of some of these boulders,
which is suggested by Clarkson et
al. to possibly be for the manufacture of quartzite Acheulean
cleavers that have been recovered from of the sites in the region.
Evidence of long-term occupation by humans that spanned about the last
80 ka has been provided by excavation sites at Dhaba. Occupation spans
the Toba eruption and it is shown by the sandstone tool industry that
there was no change in technology until microlithic technology was
introduced about 48 ka. The lithic industry from Dhaba resembles
strongly Middle Stone Age tool assemblages from Africa, Arabia and
Australia, that is interpreted here as a product of
H. sapiens as they
dispersed to the east out of Africa.
Stone artefacts
At the 3 Dhaba excavations the sequence of stone artefacts spans 55 kyr,
from about 80 to 25 ka, during which there are several distinct pulses
in artefact discard. There are 3 major technological phases that
characterise the sequence.
Dhaba 1 assemblage accumulated between about 80 and 65 ka, and is
comprised of a predominantly recurrent Levallois core assemblage that
includes centripetal, bidirectional, and unidirectional Levallois
flakes, Levallois points, Levallois blades, notches and scrapers; these
tools are made almost exclusively of chert, mudstone and silicified
limestone. Also present are multiplatform and bidirectional cores, as
well as redirecting flakes. Flakes show predominantly radial and weakly
radial scar patterning that is consistent with centripetal reduction.
There is also red ochre present in the Dhaba 1 assemblage.
Between about 55 and 47 ka Levallois technology continues to dominate
the Dhaba 2 and 3 assemblages (strata k and J at Dhaba 3, and strata I
to E at Dhaba 2) when the deposition of artefacts peaks. There is no
Levallois technology above stratum E which was dated to 47.5 ± 2 ka. At
about 48 ka microlithic technology appears in stratum D in Dhaba 2 and
stratum J in Dhaba 3, with microblades, backed artefacts and
unidirectional and bidirectional microblade cores that all appear in
these strata.
Throughout this microlithic phase quartz is the dominant material,
followed by agate. Predominantly centripetal flake scar patterning
continues to be shown until the microlithic change (strata 2D and 3G and
3H), when the dominant dorsal morphology becomes proximal and
bidirectional scar patterning. Artefact discard drops dramatically at
Dhaba 2 and 3, and very few microlithic artefacts are recovered after
this time (above strata 3C and 2D). Throughout the final period of
occupation of the site agate and chalcedony are the most common
materials, and mainly bidirectional and proximal flaking orientations
are shown by flakes. The broad changes in the proportion of key types
through time are statistically significant (Pearson chi-square = 2109;
N = 864;
p = 0.0005 one-sided).
Discussion
A key missing component in the chronological sequence is contributed by
the luminescence ages of the Dhaba locality, as well as a glimpse into
the nature of technological change that took place in India between 80
and 24 ka. The sequence closely mirrors that at Jwalapuram in southern
India (Clarkson, Jones & Harris, 2012; Clarkson et
al., 2018; Petraglia et
al., 2009), displaying a
change from recurrent Levallois technology to an increasing use of
single and multiplatform technology, and, then the manufacture of
microlithic assemblages. In both the Middle Son and the Jerreru River
valleys the technology changes appear to be stepwise, involving broad
and statistically significant changes in selection of raw materials,
changing strategies of retouching (from scrapers and points to backed
artefacts), systematic shifts in the core reduction technology, and the
introduction of new forms of retouched artefacts such as backed
microliths as Levallois technology disappears (Clarkson, Jones & Harris,
2012; Clarkson et al., 2018).
At Dhaba there is also some overlap between Levallois and microlithic
technology that occur together in stratum J in Dhaba 3 (48.6 ± 2.7 ka)
and stratum E in Dhaba 2 (47.5 ± 2.0 ka). Stratified assemblages that
span the YTT event and the transition from Levallois to microlithic
traditions are presented by the Dhaba sequence. In India, other key
sites also represent gradual changes from the Middle Palaeolithic to the
microlithic, such as Bhimbetka (Misra, 1970) and Patne (Sali, 1989),
though neither of these sites has been well dated by the use of modern
geochronological techniques and are not known to contain any traces of
YTT.
Clarkson et al. found that
the sequence offered by Dhaba is further support for the idea that
MSA-like technologies were present in India prior to and following the
YTT eruption (Petraglia et al.,
2007; Clarkson, Jones & Harris, 2012; Blinkhorn & Petraglia, 2017).
Lithic technology evolved away from Levallois towards lamella core
reduction systems, and the introduction of microlithic (in the form of
backed microblades) that most likely occurred long after the first
appearance in the region of
H. sapiens (Clarkson,
Jones & Harris, 2012; Clarkson et
al., 2018).
An exit of modern humans from Africa about 70 – 52 ka (Pagani et
al., 2016; Kuhlwilm et
al., 2016) is pointed to by
recent analyses in which all non-African people branched off from the
same ancestral population that left Africa, possibly with minor genetic
contributions from an earlier non-human migration wave (Pagani et
al., 2016; Nielsen, 2017).
Earlier dispersals of modern humans is supported by fossil evidence,
with modern humans present in Greece and the Levant by 200-185 ka (Harvati
et al., 2019; Hershkovitz,
2018), Arabia by about 85 ka (Groucutt et
al., 2018), China prior to
about 80 ka (Liu et al.,
2015), and Southeast Asia by 73-63 ka (Westaway et
al., 2017), in association
with MSA/Middle Palaeolithic technology (where stone artefacts are
present). A modern presence at the eastern end of the ‘southern arc’
dispersal route by 65 ± 6 ka, which is also indicated that groups of
modern humans are likely to have colonised South Asia prior to this
time, is documented by recent finds from Madjedbebe in northern
Australia. The strong connections between Aboriginal and South Asian
modern human genomes is consistent with dispersal through South Asia
(Atkinson, Gray & Drummond, 2007; Mondal et
al., 2016; Rasmussen et
al., 2011; Reich et
al., 2011) and admixture with
Denisovans somewhere along the route (Vernot & Pääbo, 2018; Jacobs et
al., 2019). In northern
Australia about 65 ka, the presence of centripetal and retouched point
technology, make connections with Southeast Asia, India and East Africa
much stronger that had been proposed previously (Clarkson, 2014;
Groucutt et al., 2018). These
technologies co-occur in sites east of Africa that have been dated to
between 100 and 47 ka, which suggests they were likely stepping stones
along the southern arc dispersal route (Clarkson, 2014). Quantitative
comparisons of core technologies from along the route that point to
technological continuity between Africa and Australia further support
this hypothesis. According to Clarkson et
al. the dispersal of modern
humans out of Africa, and more importantly east of Arabia, must
therefore have taken place earlier than about 65 ka, so cultural and
fossil evidence from sites that date to this period will be important
for future tests of this hypothesis, notwithstanding that population
contractions and turnovers may have also occurred. The Dhaba locality
serves as an important bridge that links regions with similar
archaeology to the east and west.
Clarkson, C., et al. (2020). "Human occupation of northern India spans
the Toba super-eruption ~74,000 years ago." Nature Communications
11(1): 961.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |