Did the wisent evolve because of humans?

For this post, I created the new post category “wild speculations”, because it is indeed a wild speculation. Some species even evolved as a result of human activities. One example for human-induced speciation would be the plant Erythranthe peregrina, which is a hybrid of two species introduced to Britain, E. guttata and E. lutea, which hybridized, created a sterile hybrid which experienced allopolyploidization (doubling of the genome) and produced a fertile hybridogeneous species. It was discovered relatively recently (2011). Without human intervention, this species would not exist. It is also possible that other kinds of human intervention, such as wiping out species, can result in a speciation event over a longer period of time in evolutionary terms because the niches that become vacant have potential for the evolution of new species. I have the suspicion that it is possible that the wisent might be such a case.

The story begins around 600kya, when there was only one Bos species in Europe, Bos (bison) schoetensacki. Around that time, a second bovine species migrated to Europe, either by island hopping from Africa or via the continental route from western Asia, the aurochs. Only a few millennia after the aurochs arrived in Europe, B. schoetensacki disappeared from the fossil record. I think it is quite possible that B. schoetensacki was outcompeted by the newly arrived aurochs as both bovines must have occupied a similar niche and the extinction shortly after the arrival of the aurochs is just as suspicious as the fact that bison subsequently were absent from interglacial faunal assemblages of Europe until the very late Pleistocene around 13kya, when bison (now in the form of the wisent) re-entered the interglacial megafauna assemblage. I call that the “bison gap” (roughly 600kya-13kya). If the aurochs outcompeted bison in Europe, why did they rejoin the interglacial fauna and why only so recently? B. bison priscus, which was most likely the ancestral form of the wisent, was present in Europe during all of the recent glacial periods. So, it could have evolved into an interglacial bison type much earlier, right after the extinction of B. schoetensacki if the aurochs did not outcompete bison in Europe – if it did, it is an open question why this competition was not a factor anymore at the end of the Pleistocene and during the Holocene.

Several thousand years earlier, there was another event that had an impact on the European megafauna: Palaeoloxodon antiquus and Stephanorhinus hemitoechus died out, most likely because of hunting from humans. Elephant extinction reduced competition for other grazers, at the same time forest growth became more common. Aurochs could not invade denser forest while bison are adapted to consume more wooden vegetation and can invade denser forest. This might have created new ecological space for bison to re-enter the interglacial faunal assemblage.

 

This guess is impossible to verify, but I think it must have one or several reasons why bison were absent from the European interglacial faunal assemblages for over 500.000 years.

 

If this guess is true, it would illustrate how nature is dynamic and might respond to anthropogenic impacts not necessarily always in a diversity-reducing way but sometimes also in a diversity-increasing way.