Australia: The Land Where Time Began |
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The Genetic Diversity and Phylogenetic Affinities of the Soliga, an
Isolated Tribe in Southern India
This study was carried out to investigate the role of tribal people, the
earliest inhabitants of India, in order to determine their role, if any,
in the dispersal of anatomically modern humans. The Soliga people are a
tribal group living in the Biligiri Rangana Hills, southern India, who
are believed to possibly be among India’s first settlers. This group of
forest-bound people speak Dravidian, practicing a subsistence level
agriculture under primitive conditions in an isolated location. This
study examined the phylogenetic relationships of the Soligas in relation
to 29 worldwide, reference populations that were geographically
targeted. Morlote et al.
employed a battery of 15 hypervariable autosomal short tandem repeat
loci as markers. It was found that the Soliga tribe were remarkably
different from other populations of India including other tribes of
southern India who speak Dravidian. Contrasting with this, the Soliga
people exhibited a genetic affinity to 2 populations of Australian
Aboriginal people. Morlote et al.
suggest that this genetic similarity could be attributed to the ´Out of
Africa´ migratory wave(s) along the southern coast of India that
eventually reached Australia. An alternative possibility is that the
genetic affinity that has been observed may be explained by more recent
migrations from the Indian subcontinent to Australia.
A number of studies have supported the pivotal role of India in the
dispersal of anatomically modern humans (Quintana-Murci et
al., 1999; Redd & Stoneking,
1999; Ingman et al., 2000;
Redd et al., 2002; Basu et
al., 2003; Cordaux et
al., 2004; Macaulay et
al., 2005; Thangaraj et
al., 2005; Sun et
al., 2006; Majumder, 2010).
It is suggested by archaeological and genetic data that the extensive
coastal area of India may have served as a route followed by human
populations as they migrated out of Africa about 70 ka (70 thousand
years ago) and settled in Southeast Asia and Australia (Quintana-Murci
et al., 1999; Macaulay et
al., 2005; Sun et
al., 2006; Kennedy et
al., 1987; Cavalli-Sforza,
1994; Lahr & Foley, 1994; Stringer, 2000; Cann, 2001; Maca-Meyer, 2001;
Lewin & Foley, 2004; Palanichamy et
al., 2004; Tanaka, 2004; Kong
et al., 2006). More than a
century ago Huxley (Huxley, 1870) noticed the similarities between some
Indian tribes and Australian Aboriginal people, leading him to suggest
an India-Australian connection. The physical similarities were
attributed by Birdsell (Birdsell, 1993) to a possible migration of
people with affinities to tribal Indians into Australia about 15,000 BP.
Birdsell hypothesised that various migratory waves shaped the peopling
of Australia. Birdsell (Birdsell, 1993) proposed that the Carpentarians,
people with physical characteristics that were similar to the Vedda
Tribe of South India and Sri Lanka, arrived through the Gulf of
Carpentaria about 15,000 BP and colonised northern and central
Australia.
A mtDNA study that argued for a recent link between Aboriginal Australia
and populations from the Indian subcontinent, supported Birdsell’s
‘multiple migrations’ hypothesis. A study by Redd et
al. later reported the
presence of a paragroup C-M216* Y-chromosome in both India and
Australia, proposing a mid-Holocene common ancestry for these
chromosomes. It is suggested by this genetic data that multiple
migrations were also supported by changes in the anthropological record
of Australia between 5,000 and 3,000 BP. Included in these changes was
the arrival of the dingo (Australia’s wild dog), that possibly arrived
from India (Gollan, 1985), the dispersal of the Australian Small Tool
tradition (Glover & Presland, 1985), the appearance of technology that
allowed plants to be processed (Beaton, 1977) and the expansion of the
Pama-Nyungan language over most of Australia (Evans & Jones, 1997),
Also, congruencies between the Pama-Nyungan and Dravidian languages were
reported by Dixon (Dix, 1980). A study published by Hudjashov et
al, (Hudjashov et
al., 2007) used the improved
resolution of the Y-chromosomal phylogeny to distinguish the Indian
C-sub-haplogroup (C5) from the Australian C sub-haplogroups (C4a and
C4b), which strongly suggested that no migrants from India reached
Australia later than the original ‘Out of Africa’ migration. The authors
did, in fact, argue that there has been no extensive genetic contact
between the first settlers of Australia and other populations, and that
it appears that Australia was largely isolated since the initial
migration (Cavalli-Sforza, Menozzi & Piazza, 1994; Kirk & Thome, 1976;
Nei & Roychoudhury, 1993). A recent study using short tandem repeats
(STRs) has, however, observed significant affinity between the Arrernte
people of Australia and populations from the Indian subcontinent
(Alfonso-Sanchez, Perez-Miranda & Herrera, 2008). It is evident,
therefore, that a clear picture is not provided by the available data of
when and how many times anatomically modern humans arrived in Australia
from India.
There have been several genetic studies (Basu et al., 2003; Cordaux et
al., 2004; Bamshad et al., 2001; Sahoo et al., 2006; Sengupta et al.,
2006) published that involved Indian populations but they failed to
reach a consensus on the origins of the casts and tribes in India. It
has been revealed by a recent genome-wide study (Beaton, 1977) that
employed more than 500,000 SNPs, that modern Indian populations are a
mixture of 2 source populations, the ancestral South Indians (ASI) and
the ancestral North Indians (ANI). Tribal people are ideal candidates
for genetic studies that seek to understand evolution of modern humans
and their migrations, including the peopling of Australia, given that
tribal people represent the original inhabitants of India (Basu et al.,
2003; Thapar, 1996; Ray, 1973; Majumder, 2008). The Soliga are a tribal
community in the Biligiri Rangana (BR) Hills, district of
Chamarajanagar, southern state of Kamataka, India. The general physical
description of the Soliga is consistent with that of the Australoid
ethnic group: dark complexion, curly hair, short stature,
dolichocephalic head, a sunken nasal root and a depressed nasal bridge
(Chopra, 1965; Morab, 1977; Majumder, 1998). Their language is
Soliganudi (Zaraska, 1997), a
dialect that has 65% lexical similarity with Kannada, a Dravidian
language that is spoken in Kamataka, Andhra Pradesh, Tamil Nadu and
Maharashtra (Gordon, 2005). The Soliga tribe is the only scheduled tribe
(ethnic minority group identified by the Indian Constitution for special
consideration (Sujatha, 2002) in the BR Hills (Morab, 1977). They are
considered among the ancient populations of India of the ‘Veddid’ type
(Dravidian speaking, forest dwelling, tribes of South India), believed
to be true autochthones (original inhabitants of a country) of India
(Sarkar, 1954). The cultural, as well as geographic isolation of the
Soligas from other populations (Morab, 1977) may be the result of their
forest-bound way of life, together with the relative inaccessibility of
the BR Hills.
Autosomal STRs are hypervariable markers that have proven to be of use
in the elucidation of recent human evolution (Rowold & Herrera, 2003).
The high resolution necessary for assessing phylogenetic relationships
among human populations that are closely related is provided by the
selective neutrality, widespread distributions throughout the genome,
abundance, large numbers of alleles and high heterozygosity of autosomal
STRs (Sarkar, 2003; Rowold & Herrera, 2003; Shepard et al., 2005;
Shepard & Herrera, 2006a; Shepard & Herrera, 2006b). Unlike the
uniparental mtDNA and Y-chromosome haplotypes, STRs and biparentally
derived, which allows for a genetic profile of the population that is
under scrutiny that is more representative.
There are 15 autosomal STR loci that were typed in the present study to
characterise the genetic diversity of the Soliga people. The researchers
then compared the allelic frequencies that were generated with other
geographically targeted populations that had previously been published
from India and other locations worldwide. Phylogenetic affinities
between the Soliga and 2 Australian Aboriginal populations the Northern
Territory were indicated by the data.
Interpopulation diversity
A CA, a NJ, dendrogram and the Carmody program’s G-test were used to
ascertain phylogenetic relationships among all populations. Admixture
analysis was used to examine genetic affinities and possible
contributions to hybrid populations.
According to Morlote et al.
there are 5 main aggregates that can be discerned within the CA plot:
1st of which consisted of all the populations of sub-Saharan Africa,
with the exception of Madagascar, a 2nd including Northeast
and Southeast Asia, a 3rd grouping all South Central Asians,
with the exception of the Soligas. A rather tight cluster, with the
exception of Rajbanshi, is formed by South Central Asia, which plots
fairly close to the Northeast/Southeast Asia, and the Soliga tribe,
which strays from the South Central Asian cluster to join the 2
Australian Aboriginal collections. The 2 southern Dravidian-speaking
tribes, Kappu Naidu and Kamma Chaudhary, as expected, show more affinity
to the Soligas than the other South Central Asian populations.
The CA graph corroborates the NJ phylogram in that 4 of the clusters in
the CA are clearly represented. Well delineated clades in the tree are
formed by the sub-Saharan African, Southwest Asian, Northeast and
Southeast Asian populations. Confirming their association in the CA, the
Soliga tribe again joins the 2 Australian populations. The populations
from South Central Asia segregate between the clades from Northeast Asia
and Southeast Asia that are in the lower half of the dendrogram whereas
the Southwest Asia and the sub-Saharan Africa clusters partition in the
upper half of the phylogram.
The group formed by the 2 Aboriginal Australian populations show the
lowest Interpopulation variance value (Gst=0.00339); however, as only 2
Australian populations, that are both from the Northern Territory, were
used in the study, it is not likely that the value reported in the study
is representative of the actual Interpopulation variance of all
Aboriginal Australian populations in the continent. The highest Gst
(0.01474) is displayed by South Central Asia, with the exception of the
all-populations group (Gst=0.02645). When the Soliga tribe is excluded
from the South Central Asia group of populations the result is a 29.25
decrease in the Gst (0.01043). Upon the removal of the Soligas this
considerable reduction in Gst argues for the genetic uniqueness of the
tribe. According to Morlote it is noteworthy that when the Soligas were
excluded, South Central Asia still has the highest Gst value for all the
remaining geographic groupings, which indicates a high Interpopulation
diversity is inherent to the region. Among the sub-Saharan African group
(Ht= 0.80274) the total variance is at its highest, closely followed by
the South Central Asian group, excluding the Soliga people (Ht=0.80059),
and next is South Central Asia, with the Soliga people included
(Ht=0.79910),
Genetic differences that are statistically significant were observed
before the Bonferroni correction was applied (α=0.05) in the following
pairwise comparisons: Kenya/Equatorial Guinea, Kenya/Angola, Qatar/Yemen
and Iraq/Yemen. When the Bonferroni correction is applied for potential
type I errors (α=0.0001149), several other pairwise comparisons were
also proven to be statistically insignificant. It was found that the
Soliga tribe differed significantly from all 29 populations it had been
compared with. Prior to the Bonferroni correction statistically
P-values are shown in bold
italic whereas P-values that
became insignificant after the Bonferroni correction was applied are
shown in bold.
Proportions of admixture were calculated for Soligas by the use of 6
parental groups, which had been established based on geographic
divisions and phylogenetic affiliations as was assessed in the CA and NJ
analyses: sub-Shahan Africa, Southwest Asia, South Central Asia,
Northeast Asia, Southwest Asia and Australia. The South Central Asian
group exhibited a contribution of 70.5% to the Soligas. According to
Morlote et al. it is
significance that the only other group that show affinity for the Soliga
genome is the from the Australian Aboriginal parental group, which
shares 29.5% of its genetic material. When the 2 Australian groups were
used as hybrids, south Central Asia was shown to be the major
contributor to both Australian Aboriginals and the declared Australian
Aboriginals (58.4 and 69.1%, respectively). Southwest Asia and
sub-Saharan Africa are, interestingly, the second (23.9%) and 3rd
(13.4%) major contributors, respectively, whereas there is no
contribution from Northeast Asia, sharing only 4.5% of its genetic
material with the Aboriginal Australians and doesn’t contribute anything
to the declared Aboriginal Australians.
Discussion
The tribal populations of India are considered to be the original
inhabitants of the subcontinent. Morlote et
al. suggest, therefore, that
it is likely that many of the questions that have been unanswered about
the evolution and migration of modern humans can be addressed by
studying the indigenous people of India. Also, the coastal route out of
Africa that was taken by modern humans that culminated in the initial
settlement of Australia is believed to include migrational distance
around the subcontinent of India, which would have provided ample
opportunity for genetic signatures to be left behind. In this study
Morlote et al. assessed the
genetic profile of the Soligas, a tribe from southern India, based on 15
autosomal STR loci. They also explored the phylogenetic relationships of
the tribe to other worldwide targeted populations.
The Soligas represent a genetic isolate in the BR Hills (Morab, 1977)
that is part of the southern state of Karnataka, India. It is
traditional for the Soliga to not interbreed with neighbouring
populations like the Kappu Naidu and Kamma Chaudhary. Morlote et
al. say there is no
information as to why the Soligas reside in this mountainous region
under conditions that are rather primitive. Yet, it is possible that as
there is no gene flow, it is possible the Soligas have maintained a
distinct gene pool. A number of population genetic parameters are a
reflection of the genetic uniqueness of the Soliga people. One is their
possession of the lowest number of alleles (115) of all the reference
worldwide populations examined. They also display the lowest average
heterozygosity that has been observed. The high degree of genetic
homogeneity that was observed could also have been the result, in part,
by the low status in the social hierarchy.
Conclusions
Both Australian Aboriginal populations from the Northern Territory and
the Soligas share their 6 most abundant alleles, though not with any of
the reference populations that were examined also suggest genetic
affinities between the Soligas and the 2 Australian Aboriginal
populations. Altogether, the data obtained by Morlote et
al. portray the Soligas as a
population with limited genetic diversity who exhibit unique genetic
characteristics which set them apart from other populations from the
Indian subcontinent. It appears to be indicated by a recent study
(Hudjashov et al., 2007) that any similarities between Indian tribes and
Australian Aboriginals result solely from genetic signals from the
original ‘Out of Africa’ migration that might have taken place more than
70 ka, further enquiry into the possibility of more recent migrations
from India to Australia is suggested by the genetic association between
the Soligas and the 2 Australian Aboriginal populations in the Northern
Territory observed in this study. Morlote et
al. suggest that a future
study that includes a larger number of tribal populations from Southern
India, as well as additional Australian Aboriginal tribes that are
defined better would be likely to shed more light on a possible
connection between India and Australia that is more recent.
Morlote, D. M., et al. (2011). "The Soliga, an isolated tribe from
Southern India: genetic diversity and phylogenetic affinities."
Journal Of Human Genetics 56: 258.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |