Weather gotras has any scientific basis? Determination of Gothras /Vamshas and ancestry?

when and who introduced the gotra/ pravara system?
our present time is in first part of kaliyuga of vaivaswat manvantar of   2nd. part of sweta varaaha kalpa.

the preceptors of our gotra system, the maharshis and their  origin  from Agni with the blessings of brahma' was happened at starting of our sweta varaha kalpa.

Bhrigu , Angira , Atri , Marichi , Pulastya , Pulaha , Vasishtha are seven great maharshis of earth introduced the gotra and pravara system.
what is gotra?  and pravara ?
'Gothra'  is  an  identity  carried  by  male  lineage  in India  from  time  immemorial.  Most  people  have  Gothra  chain  names traceable to Rig Vedic Rishis like 'Gowthama', 'Vasishta'  'Viswamithra'  and  to even first  sons  of  Vaivaswatha  Manu  like Angirasa  &  Bhrigu.  

Purana  such  as  Vishnu  Purana  refer  to  individual  identity  through  'Gothra'.  

Listings  of  more  than  250 Gothra chains have been explicitly listed. I have heard of instances of even  Muslims  converted  from  Hinduism  still  keeping  track  of  their  

'Gothra'. 

The  term  Gothra  was  used  in its  present  sense  for  the  first  time  in  the

Brahmanas by about the 4th century BC . Gothras have their orgination to saptharshies who change with Manvanthara. We are in the seventh Manvanthara now. 

The present day gotra classification is created from a core of 8 rishis. 

Vishvâmitra,  Jamadagni, 

Bharadvâja, Gautama, Atri, Vasishtha, Kashyapa and Agastya are 8 sages; the  

progeny of these eight sages is declared to be Gothras.

Gotra is the name of the founding father.  Descendents of these Rishis also started new family lineage or new gotras (Kaundinya was a descendent of Vasihta, Vishwamitra was a descendent of Kaushika and Vatsa was a descendent of Jamadagni).

The lines of descent from the major rishis are originally divided into Ganas [sub divisions] and each Gana is further divided into families. 

Pravara is the number of the most excellent rishis who belonged to that particular gotra to which the wearer of sacred thread belongs.While tying the knots of sacred thread, an oath is taken in the name of each one of these three or five of the most excellent rishis belonging to one's gotra.
is there scientific basis for gotra system ?
Genetically there was transference of some unique characteristics only from father
to son (in the form of Y-chromosomes). 
A scientific fact, that most of the male Y-chromosome is passed intact from father to son.

 Females do not carry the Y-chromosome.

The Indian mitochondria DNA pool (female ancestry) falls into just four types, attesting to how closely related all Indians are to each other.
is it useful to know gotra or genetic lineage?
geno-graphic profiles provide a way for us to understand our own origins and the migratory path of our ancestors (they may also be useful for understanding potential susceptibilities to certain diseases among  people  with  different  genetic  lineages)
Are these gotras signify the ancestors or spiritual gurus?
in the case of brahmins,gotras signify ancestoral lineage. but in respect of other varnas- kshatriyas,vaishyas, this not so,but more in connection with spiritual gurus or  purohits.

                                                       There are 49 established Hindu gotras.

Andhra kshatriyas have  10 gotras & pravara system .
        
    GOTRA                                PRAVARA.                                      pramanic veda

  Dhananjaya          Vaiswaamitra,Aghamarshana,dhanunjaya ---- sama veda

 Kasyapa -                Kasyapa, Aavatsaara, Daivala                  sama veda

 Kaundinya -           Vashista,Maitraavaruna, Kaundinya          yajurveda

 Vasistha -                Vaasishta,  MaithravaruNa,  Kaundinya  - Atharva veda

Bharadvaaja            Gautam,Bharadwaj ,Angiras                             yajurveda 

Kaushika  -           Vaiswaamitra,Aghamarshana,Koushika --- Atharva veda

vishwamitra - 

Pasupati -                       ??

Atreyasa  -           Atreya,Aarchanaasa,Syaavaasva

srivatsa -              Bhargava, Chyavana, Apnavana