http://www.blonnet.com/life/2003/06/23/stories/2003062300040200.htm
The Hindu Business Line
June 23, 2003
THE ORIGIN PUZZLE
M. Somasekhar

Breakthrough technology and findings by the Centre for Cellular and
Molecular Biology (CCMB) and several other organisations help to put
together pieces of the human gene puzzle.


In the beginning, man depended largely on historical accounts or the word of
mouth to understand his ancestry, especially on `how' and `when' his journey
on planet Earth began. Then came social anthropologists, who dug into the
sand, scooped remains of humans and animals and reconstructed pieces of
history to find continuity in human evolution. They were aided by scientific
tools like carbon dating to establish the long chain of events.
Thus, relentless searches by anthropologists in different locations in the
world, supplemented by finds by Archaeologists of human settlements, led to
the unearthing of strong evidence in the form of human remains in the
African continent during the early part of the last century. Thereafter,
Africa, the `dark continent,' has been accepted as the `cradle' of modern
civilisation.
Now, Molecular Biologists have joined the race to see whether they can
confirm this story of the homosapien so far or push his history further
back. Since the discovery of the Deoxyribonucleic Acid (DNA) structure 50
years ago, it is becoming more and more clear that the `gene,' a very tiny
portion of the homosapien holds many secrets.
By unravelling the hidden data in these genes, scientists believe they can
establish the lineage, historical time as well as susceptibility to diseases
that the modern surviving homosapien shares or differs with the ancestors.
In this pursuit, scientists at the Centre for Cellular and Molecular Biology
(CCMB), Hyderabad have made some exciting contributions.
The focus of their studies is centred around the Andaman and Nicobar
islands, where the inhabitants antecedents remain a big puzzle. The cluster
of 319 islands with an area of 8,293 sq km harbour a group of people who
have virtually locked themselves away from the modern world for centuries.
Since they were unaffected by modern developments and people outside, the
presumption was that their genetic make-up did not undergo much change and
hence offered the best window to the past history of mankind.
Ironically, what the British thought was a fit place (Open air Jail) to
banish Indian leaders fighting for freedom from their rule, has the
potential of being turned into a `Genome laboratory', which can help throw
light on not just the mysterious peoples inhabiting these Islands, but also
the exciting tales about where they came from, why they are or not
susceptible to diseases and their links (genetic) to the rest of the
populations elsewhere.
Fittingly, the pioneering study led by the CCMB also hinged again ironically
on the contributions of a Britisher - A. Radcliff-Brown, who during 1906-08
collected hair samples from the tribals on the islands (especially great
andamanese), which are now housed at the Duckworth Collection, University of
Cambridge, UK. These samples called archival hair DNA were analysed at the
Cambridge University, which was part of the global effort.
The most difficult part of the study was to get the DNA samples from the
four major tribes - Onges, Great Andamanese, Nicobarese and Jarawas. The
CCMB tied up with the Regional Medical Research Centre (RMRC), Port Blair to
collect blood samples. The Departments of Genetics at Stanford University
and Biology at the University of Oslo, Norway were also part of the Global
study team along with the Anthropological Survey of India, according to Dr
Lalji Singh, the Director of the CCMB.
The analysis of the DNA samples collected painstakingly threw up several
exciting leads. The first significant one being that the four groups of
people surviving at present on the Andaman and Nicobar islands shared a
closer resemblance to the Asian peoples than the Africans. This finding has
popped up a totally different set of questions as to how they reached
Andaman and whether there are any tribes on the Indian mainland, which
resemble them, explain Dr Lalji Singh and Dr Thangaraj of the CCMB.
A popular conjecture however is that they could have descended from a group
of people who migrated out of Africa about 60,000 years ago and were perhaps
washed ashore onto the islands by accident. The much referred to `Out of
Africa' theory of the spread of human civilisation, places the time of the
migration out of the `dark continent,' between 60,000-100,000 years ago.
The genetic data, which the researchers studied, included both the DNA from
mitochondria (which is passed on from the mother) as well as the DNA from
the Y Chromosome (inherited from the father).
Faced with these two different pointers, the CCMB team undertook DNA studies
on select tribals of the West Coast of India - Gujarat and Kerala. And to
their surprise, they found some with close affinities to the Andamanese
Negrito tribes. Negritos are an isolated group of small statured
hunter-gatherers, who share features with the African pygmies. More
importantly, these mainland tribes appear to be older than the Andamanese,
says Dr Singh.
The new twist to the entire drama has spurred the CCMB team to undertake the
DNA analysis of all the primitive tribes of India. For this, it has forged a
collaboration with the ASI. The CCMB has also embarked on the ambitious
project of creating a comprehensive gene bank of not just the endangered
tribes on the Andaman and Nicobar Islands, but also those residing on the
mainland India, so that a number of scientific studies can be taken up in
future.
The gene bank assumes significance for posterity because the numbers of
these tribes are less than four digits at present. The Onges, one of the
most primitive, hunter-gatherer tribes and fittest to survive in this
environment number just 98 as per the last count. The Sentinelese, who are
still virtually cut of from the rest of the world are estimated to number
250. The Great Andamanese are close to extinction with a total population of
36.
India is best suited to unravel the mysteries of the human evolution drama,
not just because of the fact that every sixth person on the planet lives
here today, but in India, there are 4,365 anthropologically well defined
populations, 532 are tribals and 72 primitive, and 36 are hunter gatherers,
says Dr Singh. Any conclusion on the origin of mankind has to necessarily
take into consideration India, he adds.
The study has not just thrown fresh light on the history, but has also
pointed at new opportunities in medicine. For example, the understanding of
the genetic make-up of these tribals can give an idea as to why they are
susceptible to some diseases and immune to others. If the susceptible genes
are identified, then their relationship to environmental risk factors can be
studied. This will give invaluable insights into disease patterns. For
example, some tribes in the Andamans are totally immune to malaria, while
the disease is rampant in India. By understanding this phenomenon, new
treatment methods could be possible, Dr Singh explains.
With modern medicine inclining strongly into probing the genetic links to
disease, especially the difficulty to cure one's, such studies are hoped to
be very useful. The unveiling of the human genome map a few years ago has
accelerated the understanding of genes and their role in the human body.
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