Human history through genetics

Source:  Human history through genetics    Tag:  genetic history
History:  
Our traditional history books hardly tell anything about our primal history !!

Usually they start with the available history of some civilization (say Indus Valley civilization in Indian context, which was actually a city civilization), their possible place of initial movement (say central Asia, in this example, gene study also denies the possibility of Aryan influx in great numbers ) and other civilization (say Vedic, here) started later on their ruins, etc........
 
Human history:  
It is believed that modern human species, Homo sapiens origins about 160,000 to 200,000 years ago from then Homo erectus species from a small group in African continent. 
Gradually this species of ours obliterated Homo erectus and Neanderthal as well and dominated the whole planet with their population !!


Human history hidden in our tiny cells:  
The epic history of humans is well preserved in our billions of tiny cells, which is being understood by the scientists gradually !!
A six-week-old human embryo. Photograph Getty Images
This is being explored through the genetic code language written  and preserved in DNAs with the basic four nitrogenous bases which forms the chemical languages to store our information within the 23 human chromosomes in each cell.

For this study the Y chromosomal DNA which is passed from father to the son in each progeny and Mitochondral DNAs which passes from mother's cytoplasm to each progeny with the mutations occurred during long course of time in a group is studied to trace the similarities or differences in an individual or a particular haplo group or group of humans.

So DNA molecule is like a talismatic book, where during cell division and replication of this molecule, there occurs minor changes in their chemical letters and these changes or mutations are used as identifying marks for the sake of such studies. 

"Early Train" hypothesis based on genetic analysis of mitochondrial and autosomal DNA data  
(Out-of-Africa, the peopling of continents and islands: tracing uniparental gene trees across the map)
pic credihttp://www.survivalinternational.
org/tribes/pygmies
Our human population is a progeny of an African woman some 150,000 years ago, whose genetic evidence is still present in South African San, Vianca pygmy of Central Africa, some tribes in east Africa, as they are twice ancient than the remaining in the world.

The great migration:
Scientist believe this epic journey of the ancient man might have started about 50,000 to 80,000 years ago. The first group moved from Africa to Asia and gradually populating one village and the next village, came to Indian coast, about 74,000 years ago. And in the same manner from the sea coast of Indian subcontinent, moved to Burma, to Indonesia and reached to south west coast of Australia around 45,000 years ago from now. Journey from India to Australia took 3,000 years, that means 1,200 kilometers journey was traveled with a 4 kilometer per year speed. Scientists call this journey from India to Australia as "Australia Express".

This dreamy journey of 45,000 years, populating one village after other, brave young moved ahead on further, searching for possibility of habitation in other newer places, forming more villages of human population.

In European continent, this new human species Homo erectus might have entered about 40,000 years ago, where Neanderthals had their habitation.

One branch of humans migrating from Africa, through mid Asia, China, reached to Siberia; and in the last phase of Ice age, traveled from Siberia to Alaska. Scientists believe this might have been 20,000 to 15,000 years ago from now.

pic credit:http://www.melaka.gov.my/
static/index.php/bi/community-in-melaka.
html
Remains and evidence of the movement of these human groups along with the sea coast of India, is hard to find now, as sea level has come up now 100 meters since then; and if any evidence of this sea coast travel remained, now that is under the sea. Only genetic evidence remains as our reliable guide in these studies..

But luckily there are two human groups whose study can reveal some evidence of this great epic journey. They are: Tribes of Andaman and Nicobar islands (India) and other group is Orang Asli, the original tribes of Malaysia.

These groups are the remains of the epic journey of ancient humans.

link of a related topic
http://sciencedoing.blogspot.in/2014/04/human-history-and-genetics.html

Reconstructing the Origin of Andaman Islanders
Abstract
The origin of the Andaman "Negrito" and Nicobar "Mongoloid" populations has been ambiguous. Our analyses of complete mitochondrial DNA sequences from Onges and Great Andaman populations revealed two deeply branching clades that share their most recent common ancestor in founder haplogroup M, with lineages spread among India, Africa, East Asia, New Guinea, and Australia. This distribution suggests that these two clades have likely survived in genetic isolation since the initial settlement of the islands during an out-of-Africa migration by anatomically modern humans. In contrast, Nicobarese sequences illustrate a close genetic relationship with populations from Southeast Asia.
Kumarasamy Thangaraj, Gyaneshwer Chaubey, Toomas Kivisild, Alla G. Reddy, Vijay Kumar Singh, Avinash A. Rasalkar, Lalji Singh
Science
Vol. 308 no. 5724 p. 996
DOI: 10.1126/science.1109987


Complex genetic origin of Indian populations and it's implications
Abstract
Indian populations are classified into various caste, tribe and religious groups, which altogether makes them very unique compared to rest of the world. The long-term firm socio-religious boundaries and the strict endogamy practices along with the evolutionary forces have further supplemented the existing high-level diversity. As a result, drawing definite conclusions on its overall origin, affinity, health and disease conditions become even more sophisticated than was thought earlier. In spite of these challenges, researchers have undertaken tireless and extensive investigations using various genetic markers to estimate genetic variation and its implication in health and diseases. We have demonstrated that the Indian populations are the descendents of the very first modern humans, who ventured the journey of out-of-Africa about 65,000 years ago. The recent gene flow from east and west Eurasia is also evident. Thus, this review attempts to summarize the unique genetic variation among Indian populations as evident from our extensive study among approximately 20,000 samples across India.
Rakesh Tamang, Lalji Singh, Kumarasamy Thangaraj
[Tamang R, Singh L and Thangaraj K 2012 Complex genetic origin of Indian populations and its implications. J. Biosci. 37 1–9] DOI 10.1007/s12038-012-9256-9 

Castes in India and genetics : Most Indian groups descend from a mixture of two genetically divergent populations: Ancestral North Indians (ANI) related to Central Asians, Middle Easterners, Caucasians, and Europeans; and Ancestral South Indians (ASI) not closely related to groups outside the subcontinent. The date of mixture is unknown but has implications for understanding Indian history. We report genome-wide data from 73 groups from the Indian subcontinent and analyze linkage disequilibrium to estimate ANI-ASI mixture dates ranging from about 1,900 to 4,200 years ago. In a subset of groups, 100% of the mixture is consistent with having occurred during this period. These results show that India experienced a demographic transformation several thousand years ago, from a region in which major population mixture was common to one in which mixture even between closely related groups became rare because of a shift to endogamy.
The American Journal of Human Genetics, Volume 93, Issue 3, 422-438, 08 August 2013
https://www.cell.com/AJHG/abstract/S0002-9297%2813%2900324-8)

Other references cited thankfully from:
#Resources thankfully consulted and cited for the above article from:
1. Science Reporter, CSIR, India, February 2014 issue, Gyanendra Mishra's article.

2. The American Journal of Human Genetics, Volume 93, Issue 3, 422-438, 08 August 2013
Genetic Evidence for Recent Population Mixture in India. 
Priya Moorjani, Kumarasamy Thangaraj, Nick Patterson, Mark Lipson, Po-Ru Loh, Peryasamy, Govindaraj, Bonnie Berger, David Reich, Lalji Singh
Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
Broad Institute of Harvard and MIT, Cambridge, MA 02142, USA
CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India
Department of Mathematics and Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA