Genetic testing issues in the study of ancient population migrations in India (includes info. about the Out of Africa Theory)

View previous topic View next topic Go down

Genetic testing issues in the study of ancient population migrations in India (includes info. about the Out of Africa Theory)

Post by Seva Lamberdar on Thu Jan 16, 2014 10:27 am

People have been using genetic testing in the past to investigate ancient population migrations. For example, as indicated in Appendix B in Ref. 1, if there are similarities in certain genetic markers during genetic testing on a small group of people in South India and the Middle East, that is considered as a sign of people migrating long ago in large numbers from the Middle East to South India. Similarly, if another set of genetic markers is found to match during the testing of a few persons from North India and Europe / Central Asia, it is seen as a sign of ancestors of most present day North Indians arriving long ago from Europe (Central Asia). Unfortunately, this seems like a skewed interpretation of genetic test results, looking at them in terms of ancient migrations alone and that too only in the direction of India from abroad.

For example, any similarities in certain genetic markers during genetic testing on a small group of people these days in South India and the Middle East, or in North India and Europe (Central Asia), could also be due to similar environments and lifestyles in people in South India and the Middle East, and in North India and Europe / Central Asia, and not necessarily only as a result of ancient migrations of people from the Middle East to South India or from Europe to North India.

It is generally seen that when a person or a family lives in certain place for a long time and follows certain lifestyle, especially a family living in a place for several generations, certain physical traits (related to skin color, weight, height etc. and even involving maladies e.g. heart problems and diabetes etc.) may appear in the family members due to long term effects of weather, diet and lifestyle. It is therefore natural to also expect alterations in their genetic makeup and markers, reflecting or corresponding to the changes in their physical characteristics (complexion, weight and various familial health problems, etc.) due to long term environmental effects and lifestyles.

There is now the scientific evidence available which confirms that if you take a set of “identical” twins (with similar genetic markers), separate them right after birth making them live in different places (lifestyles and environments), then after decades of living separately (in different environments and lifestyles) they acquire certain genetic characteristics (involving epigenetics) which seem different from each other. In other words, according to the excerpts below (Refs. 2 & 3), the epigenetic differences in Monozygous twins become prominent during one’s lifetime, indicating that environment and lifestyle are key factors and can influence a person genetically.

“Monozygous twins share a common genotype. However, most monozygotic twin pairs are not identical; several types of phenotypic discordance may be observed, such as differences in susceptibilities to disease and a wide range of anthropomorphic features. There are several possible explanations for these observations, but one is the existence of epigenetic differences. To address this issue, we examined the global and locus-specific differences in DNA methylation and histone acetylation of a large cohort of monozygotic twins. We found that, although twins are epigenetically indistinguishable during the early years of life, older monozygous twins exhibited remarkable differences in their overall content and genomic distribution of 5-methylcytosine DNA and histone acetylation, affecting their gene-expression portrait. These findings indicate how an appreciation of epigenetics is missing from our understanding of how different phenotypes can be originated from the same genotype. “ (Ref. 2)

“Epigenetics is emerging as an attractive mechanism to explain the persistent genomic embedding of early-life experiences. Tightly linked to chromatin, which packages DNA into chromosomes, epigenetic marks primarily serve to regulate the activity of genes. DNA methylation is the most accessible and characterized component of the many chromatin marks that constitute the epigenome, making it an ideal target for epigenetic studies in human populations. Here, using peripheral blood mononuclear cells collected from a community-based cohort stratified for early-life socioeconomic status, we measured DNA methylation in the promoter regions of more than 14,000 human genes. Using this approach, we broadly assessed and characterized epigenetic variation, identified some of the factors that sculpt the epigenome, and determined its functional relation to gene expression. We found that the leukocyte composition of peripheral blood covaried with patterns of DNA methylation at many sites, as did demographic factors, such as sex, age, and ethnicity. Furthermore, psychosocial factors, such as perceived stress, and cortisol output were associated with DNA methylation, as was early-life socioeconomic status. Interestingly, we determined that DNA methylation was strongly correlated to the ex vivo inflammatory response of peripheral blood mononuclear cells to stimulation with microbial products that engage Toll-like receptors. In contrast, our work found limited effects of DNA methylation marks on the expression of associated genes across individuals, suggesting a more complex relationship than anticipated.” (Ref. 3)

The above findings show that the environment and lifestyle do affect the genetic makeup and markers. Therefore, unless the long term influence of environments and lifestyles on the genetic markers of people living in different places (e.g. India and the Middle East etc.) can be ruled out completely and satisfactorily during genetic testing, which seems to be not the case presently, genetic testing cannot answer reliably the question of migrations of people long ago. Needless to say, the use of genetic testing for studying population migrations during ancient times appears so far highly contrived and mired with following practical, scientific and statistical issues.

(a) Firstly, on the practical side, the basis for genetic testing seems superficially narrowed down. Because genetic testing cannot establish the direction of migration long ago on its own, whether from India to outside (Middle East and Central Asia) or from outside (Middle East etc.) to India, certain preconditions are imposed to get the desired results. For example, on the basis of Out of Africa theory / model (humans originated long ago in Africa and from there spread to other places including India), it is presumed that similarities seen in genetic markers these days during genetic testing on Indians and foreigners (in the Middle East and Europe etc.) are the result of humans (ancestors) migrating long ago to India (South India and North India) from the direction of Africa (West) via the Middle East and Europe (Central Asia), respectively, and not the other way around.

There is absolutely no consideration in the above that Out of Africa model for the origin of human life could be wrong and that in reality humans could have originated instead either in another area (such as India) and spread from there to other places, or arisen “simultaneously” in a number of places independently of one another. Thus it makes little sense to stick only to Out of Africa view and discard other possibilities, such as the similarities in genetic markers currently in Indians and foreigners being the result of either similar environments in different places (South India and the Middle East, and North India and Europe / Central Asia) or people migrating long ago out of India (from South India to Middle East and from North India to Europe / Central Asia). Incidentally, as indicated in Ref. 1, the ancient linguistic and religio-cultural evidence (related to the influence of Sanskrit and Vedas abroad) seems to point that Indians at some stages in history had migrated to other lands (including the Middle East etc.). Needless to say, interpreting the genetic tests results only in terms of people moving to India from abroad seems quite shortsighted and erroneous.

In any case, a handful of people (bandits and invaders etc.) supposedly arriving in India from abroad on a number of occasions long ago, taking over the country, marrying or impregnating many local women and producing numerous offspring would not make majority of present Indians having foreign roots. Most of the sons and daughters born to the original foreign invaders and settlers with Indian mates would have half Indian blood and half foreign blood. When these children of foreigners, carrying half Indian and half foreign blood (genetic markers), would choose and marry mates mainly from the vast indigenous Indian population, they would produce children who would have only one-fourth foreigner blood and three-fourth Indian blood (genetic markers).

This process of marrying repeatedly over the generations into the local / indigenous population in India would ultimately lead to the children (the present day Indians basically) whose blood and genetic markers would be mostly or entirely (in case they never had the foreign input) indigenous (similar to the existing in India prior to the arrival of foreigners long ago) and have very little or nothing in common with the original foreign blood and genetic markers. It seems silly therefore for anyone to imply that most people in India these days are of foreign origin. Moreover, even if some people outside India are seen these days having a few genetic markers which seem similar to a few genetic markers in people in India that could also be the result of similarity in environments and lifestyles in India and foreign places or perhaps people from India migrating abroad long ago.

Furthermore, when people imply these days that due to ancient migrations from outside to India long ago (40000 years or 20000 years earlier) the vast numbers of South Indians (20%, 30% or 50% population in South India) now share certain genetic markers with people in the Middle East or that a large percentage of North Indians (20%, 30% or 50% population in North India) now share genetic markers with people in Europe (Central Asia), there is no explanation for the total absence, or presence only to a very small degree (in less than 10% population), for those special genetic markers with other Indians (North Indians now usually lacking the Middle Eastern genetic markers and South Indians lacking the European / Central Asian genetic markers).

Considering the special genetic markers could travel long ago in abundance (affecting 30% to 50% of Indian population today) over thousands of rugged and treacherous miles to South India from the Middle East and from Europe / Central Asia to North India, then what halted their significant spillover and spread across the puny Vindhyas into North India (for Middle Eastern genetic markers via South India ) and South India (for European / Central Asian genetic markers via North India), initially (at the time of arrival from the Middle East or Europe / Central Asia) and during the subsequent thousands of years?

The inability to answer these questions satisfactorily in terms of migrations and movement of people long ago indicates that whatever similarities in genetic markers are there now in people in the Middle East and large population in South India, or people in Europe / Central Asia and large population in North India, are probably the result of long term similar environments and lifestyles etc. in these places (the Middle East and South India, and Europe /Central Asia and North India), and nothing else. For example, if the reasons for the presence of genetic markers from the Middle East and Europe / Central Asia in large numbers of South Indians and North Indians, receptively, were the long ago migrations, then they would also be present significantly now, after spilling over the puny Vindhyas (initially or during several millennia after their initial arrivals) in North Indians and South Indians, respectively. But that is not the case according to the genetic tests.

This type of anomaly in genetic marker behavior (their inability to travel across the puny Vindhyas after initial crossing over thousands of rugged and treacherous miles and then affect 25% to 50% population in North India and South India, as claimed by the testers) also points to discrepancies in genetic testing, including perhaps the insufficient sample sizes and misinterpretation of results.

(b) Scientifically, as indicated earlier, there is a significant influence of environment and lifestyle on the genetic markers during one’s lifetime, at least epigentically. In addition, the genetic effects of environment and lifestyle would very likely compound over the millennia and might shield and overlap the genetic effects (markers) due to initial migration. There is no way currently to properly identify and separate genetic markers due to long term environmental influences (including lifestyles) and those from initial migrations or people moving back and forth later. This makes the findings from current genetic tests meaningless, since they are attributed only to the migrations to India long ago. Anyway, according to linguistic and religio-cultural similarities in India and abroad (including the influence of Sanskrit and Vedas, Ref. 1), the idea of uni-directional migrations (to India only) in these tests seems to be seriously flawed.

Note also that the current Out of Africa model, which presumes (on the basis of a few discoveries of earliest human remains / fossils in Africa) that humans originated in Africa and migrated to other places and which is used now to standardize the genetic markers routes (people and their genetic markers moving away from Africa), is less scientific and more coincidental. The lack of discoveries of similar ancient human remains in other places (such as India) so far does not prove that humans might not have originated elsewhere. Perhaps the ancient human remains (even older than those discovered in Africa) existed in other places but were lost over time due to heightened human and natural activity in those places (much more than the activity in Africa).

It makes little sense therefore to consider genetic testing as a reliable tool to study the ancient migrations (specifically in deciding the direction of movement of people long ago) while using a hypothesis (Out of Africa theory) which may or may not be valid. There seems little from these genetic testis, except probably to identify a few matching genetic markers which might be the result of similar long term environmental influences and lifestyles and / or people migrating in and out of India long ago. In addition, based on the nature of these genetic tests (using small sample sizes), the extrapolation of results to entire populations living in large areas currently (in South India and the Middle East or in North India and Europe / Central Asia) seems not justifiable.

(c) Statistically, it makes little sense to test a few people (representing very small sample sizes) in different places these days and then use similarities in their few genetic markers as the proof of uni-directional (towards India) migrations of ancestors of hundreds of millions (even billions) of people living in many countries, even implying that 20%, 30% or 50% of these millions / billions of people now share the same genetic markers. Note, even when there is a need to decide the paternity issue for two brothers, who are born from the same mother, each of them has to individually go through the genetic test against “father”. The proof of one brother’s paternity is not automatically accepted as applicable to other brother. Thus it seems quite farfetched when some people use the results from genetic tests on small groups of people as the evidence for ancestors of hundreds of millions of people living in different places migrating long ago in a special way.

In conclusion, it is clear from the above that the use of genetic testing for deciding the migrations of populations in India long ago gives rise to serious practical, scientific and statistical issues. The findings from these genetic tests therefore seem quite questionable.

References:

(1) Subhash C. Sharma, “On the origins of the Vedas and Sanskrit (including the Aryan Invasion Theory), Aug. 21, 2012, http://lamberdar.hubpages.com/hub/origins-of-vedas-and-sanskrit

(2) “Epigenetic differences arise during the lifetime of monozygotic twins,”
Edited by Stanley M. Gartler, University of Washington, Seattle, WA (received for review January 17, 2005), http://www.pnas.org/content/102/30/10604.short

(3) “Factors underlying variable DNA methylation in a human community cohort,” Edited by Gene E. Robinson, University of Illinois at Urbana–Champaign, Urbana, IL, and approved August 22, 2012 (received for review March 30, 2012), http://www.pnas.org/content/early/2012/10/04/1121249109.short

by; Dr. Subhash C. Sharma

Ref.: http://lamberdar.hubpages.com/hub/genetic-testing_population-migrations
avatar
Seva Lamberdar

Posts : 4862
Join date : 2012-11-29

View user profile https://docs.google.com/document/d/1bYp0igbxHcmg1G1J-qw0VUBSn7Fu

Back to top Go down

View previous topic View next topic Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum