It has long
been established that the aurochs can be divided into several mainland
subspecies: B. p. namadicus, the Indian (South-Asian) one, B. p. mauretanicus
(African), B. p. primigenius (European) and B. p. suxianensis (East-Asian).
I was not entirely happy with this taxonomy, as it is clear that they are not distinct,
isolated clades but have a continuous range and the morphological differences
between them are more like tendencies (such as that East-Asian ones tend to
have a convex snout but these are not exclusive to them etc.) rather than clear
autapomorphies. Recent genetic analyses suggest that the idea of mainland aurochs
subspecies tied to certain regions is not tenable and that the evolutionary
history of the aurochs was much more complex than what a taxonomy with four mainland subspecies would suggest. The island subspecies, however, are – at least in my
opinion – a different story as they were clearly reproductively isolated for at
least a certain amount of time. Two studies are of particular relevance for the
phylogeny of wild Bos primigenius (or Bos taurus,
depends on what you prefer).
Rossi et
al., 2024: The genomic natural history of the aurochs.
38 aurochs
genomes from the Late Pleistocene to Holocene were analyzed. The lines of
taurine and indicine cattle diverged around 166-300kya. Taurine-line aurochs
and indicine-line aurochs descend from a common population that lived around
390kya. Within the taurine-line aurochs, North Asian aurochs separated from
Southwest-Asian aurochs after 100kya, splitting from a common ancestral
population. More archaic aurochs, however, left a minor trace in those later taurine-line
aurochs. The North-Asian aurochs haplogroups C and K split from the other
taurine-line haplogroups P, Q, T, E and R around 96 to 72 kya.
Zhu et
al., 2025: Revisiting aurochs haplogroup C: Paleogenomic perspectives from
Northeastern China.
It covers
all the mitochondrial haplogroups P, T, E, Q, R, G, K, C, I and shows a phylogenetic
cladogram. The Central Asian haplogroup G is the basalmost one, basal to the
group taurine + indicine line and separated around 400kya. R, so far found in
North African aurochs, is closer to a clade of K and C from Asia than to T or
P.
What is
surprising to me is that the split between the taurine-line aurochs and
indicine-line aurochs is that recent. This means that most namadicus fossils,
which are from the Middle Pleistocene to the early late Pleistocene, cannot be
considered ancestors of the zebu any more than other archaic aurochs from that
time. It also means that the 700.000 year old Wadi Sarrat skull from Tunisia
does not belong to the same line as late North African aurochs but is much more
basal.
Looking at
the phylogeny of the various aurochs haplogroups and comparing it to their
location it becomes clear that the aurochs genomic history is much more
complicated than a subdivision into four mainland subspecies would suggest. As
Rossi et al. and Zhu et al. note, the range of the aurochs likely expanded and
contracted with the countless climate oscillations during its existence, and
looking at the relationship between R (North African) and K/C (Asia), clearly a
lot of migration must have been involved.
I think
that, based on the phylogeny of the various aurochs lineages, it is not useful
to subdivide the mainland populations into subspecies. Especially as the type
specimens for the respective subspecies taxa are not publicized (with the
exception of B. p. primigenius, the Haßleben aurochs), which would be
necessary to see which taxon equates to which genetic lineage. Apart from that,
it would be of limited use to erect a subspecies taxon for each haplotype or
genetic lineage given the diversity found within the aurochs. And we only know
about half of the diversity found within the species, given that we do not have
genomes from earlier aurochs. So now we know that there were non-crown-group
aurochs in the late Pleistocene, that the split between indicine-line aurochs
and taurine-line aurochs occurred fairly recently.
