Background
The Gotra system in many parts of India is a peculiar feature of patri-linear society. For eg. in societies of Kerala where matrilinear system is followed, Gotras don't exist in the same way as in Patri-linear societies.
Based on this there is an understanding that Gotra is all about genes of Y Chromosomes. My understanding is that it's a misconception. In my view, Gotra has nothing much to do with genes of Y Chromosomes.
Some facts about Y Chromosomes
Unlike all other chromosomes, the Y is genetically isolated; Hence it has shrunk dramatically over our evolution. The 22 pairs of autosomes and X chromosome (in case of XX) are able to pair up, allowing for a process known as homologous recombination to occur in meiosis. During recombination, the two members of an autosome pair are able to cross-over, exchange genetic material with each other, and notably, swap faulty genes for good ones by using each other as templates. This process allows for the repair of damaged chromosomes that may have resulted from mutations.
Over the past 300 million years, however, because the Y has gradually become less homologous to the X, cross-over between the sex chromosomes has become drastically reduced. Thus, the vast majority of the Y suffers from the detrimental effects of suppression of recombination. In the non-recombining MSY, mutations accumulate, uninhibited and unrepairable. As a consequence, active genes on the Y are rapidly lost, and the Y is subject to considerable degradation and decay.
Gotra system cannot save the Y Chromosomes from these effects. Female of any Gotra will never have Y chromosome. So in a male-female union there is always going to be a single Y chromosome. Hence from which gotra male came or female came does not matter.
Gotra System – A ‘Wholistic’ system to avoid in-breeding
Not just in Humans, even in Chimpanzees, females move over to other groups on reaching puberty (1). It is like women is given off in marriage or taken in a marriage. The reason for this is males who grew up together are well knit in defending, attacking, collecting food, strategizing etc. To avoid in-breeding within groups, generally females move out. This is the basis of patriarchal system.
Hence Gotras (which means large community living together, cow-shed) became based on male's lineage.
Take an example of a large parti-linear family living in a single community. It is patr-linear because women move out of the community.
It is possible that males in a lineage have the exact replica not just in terms of sex chromosomes but all the 23 pairs. It is possible that a women belonging to the same Gotra have a good replica of their chromosomes similar to the male of that Gotra, except for the Y part. Hence if a women belonging to same Gotra, which means woman in the same community, get married to males in the same community, it becomes equivalent to in-breeding. In-breeding propagates genetic defects and does not give natural selection a chance to tide over them. To avoid it, marriages within the same Gotras are avoided. (So it is not for avoiding defects in Y chromosome).
Now, if the women move out and marry a male of another patri-linear group, it is possible that they may have similar genetic make-up. But the possibility gets reduced as the gotra system is followed over several generations, as different groups gets separated.
In fact in the olden days, gotras of both parents were avoided for marriage. Then those gotras whose rishis were more common were avoided. Now gotra of the father alone is avoided. All these were to give natural selection a good chance.
Gotra system of Seven Rishis
The seven rishis (Sapta Rishis) who started the Gotras might have any kind of chromosomes with any kind of defects. But by becoming the root and ensuring their lineages do not further in-breed within them, they have given natural selection a chance over the human desires, thus trying to wash away the defective genes over a period of time.
If there is a matriarchal system, in which women stay together and males go out, as in mountaneous regions, patri-linear gotra system is not followed.
References
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826206/
Ref
The Gotra system in many parts of India is a peculiar feature of patri-linear society. For eg. in societies of Kerala where matrilinear system is followed, Gotras don't exist in the same way as in Patri-linear societies.
Based on this there is an understanding that Gotra is all about genes of Y Chromosomes. My understanding is that it's a misconception. In my view, Gotra has nothing much to do with genes of Y Chromosomes.
Some facts about Y Chromosomes
Unlike all other chromosomes, the Y is genetically isolated; Hence it has shrunk dramatically over our evolution. The 22 pairs of autosomes and X chromosome (in case of XX) are able to pair up, allowing for a process known as homologous recombination to occur in meiosis. During recombination, the two members of an autosome pair are able to cross-over, exchange genetic material with each other, and notably, swap faulty genes for good ones by using each other as templates. This process allows for the repair of damaged chromosomes that may have resulted from mutations.
Over the past 300 million years, however, because the Y has gradually become less homologous to the X, cross-over between the sex chromosomes has become drastically reduced. Thus, the vast majority of the Y suffers from the detrimental effects of suppression of recombination. In the non-recombining MSY, mutations accumulate, uninhibited and unrepairable. As a consequence, active genes on the Y are rapidly lost, and the Y is subject to considerable degradation and decay.
Gotra system cannot save the Y Chromosomes from these effects. Female of any Gotra will never have Y chromosome. So in a male-female union there is always going to be a single Y chromosome. Hence from which gotra male came or female came does not matter.
Gotra System – A ‘Wholistic’ system to avoid in-breeding
Not just in Humans, even in Chimpanzees, females move over to other groups on reaching puberty (1). It is like women is given off in marriage or taken in a marriage. The reason for this is males who grew up together are well knit in defending, attacking, collecting food, strategizing etc. To avoid in-breeding within groups, generally females move out. This is the basis of patriarchal system.
Hence Gotras (which means large community living together, cow-shed) became based on male's lineage.
Take an example of a large parti-linear family living in a single community. It is patr-linear because women move out of the community.
It is possible that males in a lineage have the exact replica not just in terms of sex chromosomes but all the 23 pairs. It is possible that a women belonging to the same Gotra have a good replica of their chromosomes similar to the male of that Gotra, except for the Y part. Hence if a women belonging to same Gotra, which means woman in the same community, get married to males in the same community, it becomes equivalent to in-breeding. In-breeding propagates genetic defects and does not give natural selection a chance to tide over them. To avoid it, marriages within the same Gotras are avoided. (So it is not for avoiding defects in Y chromosome).
Now, if the women move out and marry a male of another patri-linear group, it is possible that they may have similar genetic make-up. But the possibility gets reduced as the gotra system is followed over several generations, as different groups gets separated.
In fact in the olden days, gotras of both parents were avoided for marriage. Then those gotras whose rishis were more common were avoided. Now gotra of the father alone is avoided. All these were to give natural selection a good chance.
Gotra system of Seven Rishis
The seven rishis (Sapta Rishis) who started the Gotras might have any kind of chromosomes with any kind of defects. But by becoming the root and ensuring their lineages do not further in-breed within them, they have given natural selection a chance over the human desires, thus trying to wash away the defective genes over a period of time.
If there is a matriarchal system, in which women stay together and males go out, as in mountaneous regions, patri-linear gotra system is not followed.
References
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826206/
Ref
