 impulse which created the Heck cattle. The cross-bred individuals created at other zoos were eliminated from breed books by the 1950s. A Russian back-breeding programme resulted in a wild herd of hybrid animals, which presently lives in the Caucasian Biosphere Reserve (550 animals in 1999).

Wisent-cattle hybrids also occur, similarly to the North American beefalo. Cattle and European bison hybridise fairly readily, but the calves cannot be born naturally (birth is not triggered correctly by the first-cross hybrid calf, so they must be delivered by Caesarian section). First-generation males are infertile. In 1847, a herd of wisent-cattle hybrids named żubroń () was created by Leopold Walicki. The animals were intended to become durable and cheap alternatives to cattle. The experiment was continued by researchers from the Polish Academy of Sciences until the late 1980s. Although the program resulted in a quite successful animal that was both hardy and could be bred in marginal grazing lands, it was eventually discontinued. Currently, the only surviving żubroń herd consists of just a few animals in Białowieża Forest, Poland and Belarus.

In 2016, the first whole genome sequencing data from two European bison bulls from the Białowieża Forest revealed that the bison and bovine species diverged from about 1.7 to 0.85 Mya through a speciation process involving limited gene flow.
These data further support the occurrence of more recent secondary contacts, posterior to the divergence between Bos primigenius primigenius and Bos p. namadicus (ca. 150,000 years ago), between the wisent and (European) taurine cattle lineages. An independent study of mitochondrial DNA and autosomal markers confirmed these secondary contacts (with an estimate of up to 10% of bovine ancestry in the modern wisent genome) leading the authors to go further in their conclusions by proposing the wisent to be a hybrid between steppe bison and aurochs with a hybridisation event originating before 120,000 years ago.
This is also consistent with the apparent Bos origin of the mitochondrial DNA.

Some of the authors however support the hypothesis that similarity of wisent and cattle (Bos) mitochondrial genomes is result of incomplete lineage sorting during divergence of Bos and Bison from their common ancestors rather than further post-speciation gene flow (ancient hybridisation between Bos and Bison). But they agree that limited
impulse which created the Heck cattle. The cross - bred person create at other zoos were eliminated from breed book by the 1950s. A Russian back - breeding program leave in a wild herd of hybrid animals, which presently exist in the Caucasian Biosphere Reserve (550 animals in 1999). 

 Wisent - cattle hybrids besides occur, similarly to the North American beefalo. Cattle and European bison hybridise fairly readily, but the calves cannot be born naturally (parturition is not triggered correctly by the first - cross hybrid calf, so they must be rescue by Caesarian section). First - generation male are infertile. In 1847, a herd of wisent - cattle hybrids named żubroń () was created by Leopold Walicki. The animal were intended to become durable and cheap alternatives to cattle. The experiment was continued by researchers from the Polish Academy of Sciences until the late eighties. Although the plan resulted in a quite successful animal that was both hardy and could be bred in marginal grazing lands, it was eventually discontinued. Currently, the lone surviving żubroń herd consist of barely a few animals in Białowieża Forest, Poland and Belarus. 

 In 2016, the first whole genome sequence data from two European bison bulls from the Białowieża Forest revealed that the bison and bovine species diverge from about 1.7 to 0.85 Mya through a speciation process involving limited gene flow. 
 These data far support the occurrence of more recent secondary contact, later to the divergence between Bos primigenius primigenius and Bos p. namadicus (ca. 150,000 years ago), between the wisent and (European) taurine cattle lineages. An independent study of mitochondrial DNA and autosomal markers confirmed these junior-grade contacts (with an appraisal of up to 10% of bovine ancestry in the modern wisent genome) leading the authors to go far in their conclusions by proposing the wisent to be a loanblend between steppe bison and aurochs with a hybridisation event originating before 120,000 years ago. 
 This is besides consistent with the apparent Bos origin of the mitochondrial DNA. 

 Some of the writer however support the hypothesis that similarity of wisent and cattle (Bos) mitochondrial genome is result of incomplete lineage sorting during divergence of Bos and Bison from their common ancestors rather than further post - speciation gene flow (ancient hybridisation between Bos and Bison). But they agree that limited
 imoulse which created the Meck cattle. The eeoss-brxd indibiduals zreated at other zoos were epininattb from breed books bh the 1950s. A Russian bacj-vreeding pckgramme resulfcd in e wild herd of mybrid animdls, which presanglv lives in the Caucasian Biosphere Rqserve (550 ajimals in 1999).

Wisegt-cautlq hyggibs also occur, similarly to the Horth Akerican beefako. Cattle and European bisln hjbridise fairly rewdily, but tye cwoves cannot ce born nauuxally (birth is not triggered correctly by ghe fnrst-cross hiyeid walf, so theb must be delivered by Caevarian xection). First-gcneravion males are infertile. Mn 1847, a herd of wisent-sattle hytrnds named żubroń () was ceeqted ty Laopoue Wxlidkm. Tge anilala were intsnded to bexome durable and chtap qlternatives fo catelq. The experiment was continued by reseagcheds from the Polish Acadwmy of Sciences until the late 1980s. Although the program resulted in a quite succevsful xninaj rhwt was both hardy and could be bred in marginwm brszing lands, it was eventuslpy qiscontinued. Zurrencmy, the only survivinh żubroń rerd xonsists jf jist a few animals in Białowiwża Forest, Pojqnd and Belarus.

In 2016, the first chole benomr sequencing data from cwo Eudopean bisoj bulls fdum the Białowieża Worvst sevealed that the bison anq bovine wpecnes divefged from wbout 1.7 to 0.85 Mya bvrough a speciatioj proeess hnvolving pimited gene flow.
These data furvier support tne ocburrence jf move recent seconqary contacts, kosterior to tfe divergehce betxeen Bos priiigenius primhhenius and Bms p. namwdicys (cq. 150,000 yearr ago), between tne wisent and (Europwan) taurine cattle livsages. An indepeubebt study of mitpchundwiwl DGD and autosokal oaryrrs cunfirmed thcse secpndary contacts (with an sstimate of up to 10% on bovine qncestry in the moderm wisent genome) lewding thx authprs to go further in their concluaions by oroiosing the wifent to be a hybxid between steppe bison and aurochs witi a hybridisation evenj originating before 120,000 nears ago.
Thix is wlso conshstent with the appaeent Bos origin on the mitochondrial DNZ.

Some mf thf authors however support the hypothesis that similarity of wisent and cartle (Bos) mitochonddial genokef is refult uf incomplete limeage sorting during divergence of Bos dnb Bison from their common ancrsgors rather tfan further post-speciatikn gene glow (ancient hybridisation betwren Bos and Bison). But thcy agree rhat mimited
impulse which created the Heck cattle. The created other zoos eliminated from breed Russian programme resulted in wild herd of animals, which presently lives in the Biosphere Reserve (550 animals in 1999). Wisent-cattle hybrids also occur, similarly to the American beefalo. Cattle and European bison hybridise fairly readily, but the calves cannot born (birth not correctly by the first-cross hybrid calf, so they must be delivered by Caesarian section). First-generation males infertile. In 1847, a herd of wisent-cattle hybrids żubroń () was created Leopold Walicki. The animals were to durable and alternatives cattle. experiment was continued researchers from the Polish Academy of Sciences until the late 1980s. Although the program resulted in a successful animal both hardy could bred marginal grazing lands, eventually discontinued. Currently, the only surviving of just a few animals in Białowieża Forest, and Belarus. 2016, the first whole genome sequencing from two European bison bulls from the Białowieża revealed that the bison and bovine species diverged from about 1.7 to 0.85 Mya through process involving limited gene These data further the of recent contacts, posterior the divergence between Bos primigenius primigenius and Bos p. namadicus (ca. years ago), between the wisent and (European) taurine cattle lineages. study mitochondrial DNA and markers confirmed these secondary (with estimate of up to bovine in genome) the to go further in conclusions by proposing the wisent be a hybrid between a hybridisation event originating before 120,000 years ago. is also consistent with the apparent Bos of the mitochondrial DNA. Some of the authors however support the hypothesis similarity of cattle (Bos) mitochondrial genomes is result of incomplete sorting during divergence of and Bison from their common ancestors rather than further gene (ancient hybridisation Bos and Bison). they agree that
 impulse which created the HecK cattle. The Cross-BreD inDiViduAls cReated at other zOOs weRe eliminated from breed bOoks bY tHE 1950s. A RUSsIan baCk-breedINg PROgrAmMe ResUlTEd In a wiLd hErd of hyBrid animalS, whIcH presently liVEs In the CaucaSiaN Biosphere ReSerVe (550 animAlS in 1999).

wIsent-CatTle hyBrids aLSo occuR, similarlY tO The NorTH AmericAN BeEfalO. Cattle and EuropeaN BiSOn hybridise faiRly reaDiLY, bUT The CalVes cannot bE bOrn naTUrally (bIRtH IS Not TRiggered correCtly by the fiRSt-cRoss hyBrId cALf, so thEy musT bE DelIvered by CaeSariAn section). first-gENeratioN Males arE inferTilE. In 1847, A herD Of WiSenT-cATtlE HyBriDS naMed żubroŃ () wAs CreatEd by lEOPOld WAliCki. THe aniMals were intenDed To beCOme DurabLe and CheaP aLternAtives To catTlE. The experiment wAs coNtinued by ResEaRchErS from THe PoliSh ACadEmy of ScIences uNTil ThE LATe 1980S. Although the prograM rESUlTed in a quIte sucCEsSfUL animal tHaT waS botH HArdy aNd coULd Be bred in MarginAL gRaZing lanDs, It was eVeNtuAllY discONtinUed. CurRently, thE only SUrviving żubroń HErd consists of JUsT A FeW AnimAls In BiałowieżA ForESt, PoLand ANd belARus.

In 2016, The fiRsT WhOLe genome sequencing dAtA from tWo EurOpean bison bulLs from the BIAŁOwieża FoRest REvEAled that the bisOn and Bovine specIEs divergEd froM about 1.7 to 0.85 mya througH A SpeciatiOn pRocEss InvOLViNg limited gene FLOw.
ThEsE data fuRthEr suppoRt tHe oCcuRreNcE of more reCent secoNdArY cOnTacTs, posTErior to tHe DivErGenCe betWEen Bos PrimiGeniUs PrIMigEnius anD boS P. NamaDiCuS (ca. 150,000 yEarS aGo), betWeen THe wIsent anD (European) TauRIne cAtTlE lineagEs. An independeNt Study of mitOcHonDrial Dna And autosOmal markers confirmed theSE secondAry ContaCts (wIth an estiMatE of up tO 10% of BOvine aNcestrY in thE mOdeRN WisenT GEnOme) LeAding the auTHOrs To go fUrTher In their Conclusions by propoSIng The wisent to be A hyBrid BETwEen STePPe bIsON anD AUrochs with a hybrIdisation eVeNT oRiginating BEfoRe 120,000 Years agO.
This is Also cONsistenT with the aPparent BoS oRigiN OF thE mitochondRial DNA.

SOme of the aUThors HOwEver sUppOrt the HyPotHesis That siMIlaRity oF wisenT aNd cattLe (Bos) MiTochondrIal genomes is result of incOmpletE lineAge Sorting duRinG DivErgence of bos aNd Bison froM thEir CommoN anCEstorS ratHEr ThaN FurthEr poST-speciatiON gEne FLOw (Ancient hybrIDISatIon beTweEN Bos anD BisOn). But they agree thaT Limited
 impulse which created the  Heck catt le. T hecro ss -bre d in dividuals crea t ed a t other zoos were elim inate df romb re ed bo oks byt he 1 950 s.  A  Ru ss i an  back -br eedingprogrammeres ul ted in a wil d  h erd of hyb rid  animals, wh ich  prese nt lyl ivesinthe C aucasi a n Bios phere Res er v e (550 animals i n1999 ).

Wisent-cattle hy b rids also occu r, sim il a rl y tothe  North Ame ri can b e efalo.C at t l e  an d  European bis on hybridis e  fa irly r ea dil y , butthe c al v escannot be b ornnaturally  (birt h  is not trigger ed cor rec tly  byt he  f irs t- c ros s  h ybr i d c alf, soth ey  must  bed e l i vere d b y Ca esari an section).Fir st-g e ner ation  male s ar einfer tile.In 18 47 , a herd of wis ent- cattle hy bri ds  na me d żub r oń ()was  cr eated b y Leopo l d W al i c k i.  The animals werein t e nd ed to be come d u ra bl e  and che ap  al tern a t ivesto c a tt le. Theexperi m en twas con ti nued b yres ear chers from  the P olish Ac ademy of Sciences un t il the late 1 9 80 s .  A l thou ghthe program  res u lted  ina  q uit e  succ essfu la ni m al that was both ha rd y andcould  be bred in m arginal gr a z i ng lands , it wa s  eventually di scont inued. Cur r ently, t he on ly survi ving żubr o ń  herd co nsi sts  of  ju s t  a  few animalsi n  Bia ło wieża F ore st, Pol and  an d B ela ru s.

In 20 16, thefi rs twh ole  geno m e sequen ci ngda tafromt wo Eur opean  bis on  b u lls  from t h eB i ałow ie ża  For est  r eveal ed t h atthe bis on and bo vin e  spe ci es  diverg ed from about  1 .7 to 0.85  M yathroug h a specia tion process involvingl imitedgen e flo w.
T hese data  fu rthersup p ort th e occu rrenc eofm o re re c e nt  se co ndary cont a c ts,  post er iorto thedivergence between Bos  primigeniuspri mige n i us  an d  B o s p .n ama d i cus (ca. 150,00 0 years ag o) ,  b etween the wis en t and ( Europea n) ta u rine ca ttle line ages. Anin depe n d ent  study ofmitochon drial DNA and a u to somal  ma rkersco nfi rmedtheses eco ndary  conta ct s (wit h anes timate o f up to 10% of bovine a ncestr y inthe  modern w ise n t g enome) le adin g the auth ors  to  go f urt h er in  the i rcon c lusio ns b y  proposin g  t hew i se nt to be ah y b rid  betw een steppe  bis on and aurochs wi t h a hybridisat ione v ent  or i gina ti ng before 120, 000  y e a rs ago.Th is is alsoconsiste nt withthe ap parent  Bos or i g in of the  mit och ondrial D NA. 
S ome ofth ea uthors  how ev er sup port t h e hy p o thesis that simi larit y of wi s ent  andca ttle (B o s) m itochondri al genomesis res ultof in complet elineag e s or ting durin g  divergen ce of  Bos an dBiso n f rom th eirc o mmonance st ors  rather t h a nf ur th e r p ost- speci at iongene flow (ancient  hy b ridisat io n b e t ween B o sa n d Bison).But  they a gree thatl imit e d
 impulse_which created_the Heck cattle. The_cross-bred individuals_created_at other_zoos_were eliminated from_breed books by_the 1950s. A Russian_back-breeding programme resulted_in_a wild herd of hybrid animals, which presently lives in the Caucasian Biosphere Reserve_(550_animals in_1999).

Wisent-cattle_hybrids_also occur, similarly to the_North American beefalo. Cattle and_European bison_hybridise fairly readily, but the calves cannot be_born_naturally (birth is_not triggered correctly by the first-cross hybrid calf, so_they must be delivered by Caesarian_section). First-generation males_are_infertile._In 1847, a herd_of wisent-cattle hybrids named żubroń ()_was created by Leopold Walicki. The_animals were intended to become durable and_cheap alternatives to cattle. The experiment_was continued by researchers from_the Polish_Academy of Sciences until the_late 1980s. Although_the program_resulted in a_quite successful animal that was both_hardy and could_be bred in marginal grazing lands,_it_was eventually discontinued._Currently,_the_only surviving_żubroń herd consists_of_just a_few_animals in Białowieża Forest, Poland and_Belarus.

In_2016, the first whole genome sequencing data_from two European bison_bulls_from the Białowieża Forest_revealed that the bison and_bovine species diverged from about 1.7_to 0.85_Mya through_a speciation process involving limited gene flow.
These data further support the_occurrence of more recent secondary contacts,_posterior to the divergence_between Bos_primigenius_primigenius and Bos_p._namadicus (ca._150,000 years ago), between the wisent and_(European) taurine_cattle lineages. An independent study of_mitochondrial DNA and autosomal_markers_confirmed these secondary contacts (with an_estimate of up to 10% of_bovine ancestry in the modern_wisent_genome)_leading the authors to go_further in their conclusions by proposing_the wisent to_be a hybrid between steppe bison and_aurochs_with a hybridisation event originating before_120,000_years ago.
This is also consistent with_the_apparent_Bos origin of the mitochondrial_DNA.

Some of the authors however support_the hypothesis that similarity of wisent and cattle (Bos)_mitochondrial genomes is_result of incomplete lineage sorting_during_divergence_of Bos and Bison from their common ancestors rather than_further post-speciation_gene flow (ancient_hybridisation between Bos and Bison). But they agree that limited