Back in a 2013 post, I called Maronesa a “relict breed” from Portugal. Not because of an alleged isolated ancient origin, but for its flawlessly aurochs-like colour make-up, the well-expressed sexual dimorphism and the inwards-facing horn curvature.
Now there is a kind of quarrel on the English Wikipedia page regarding the origin of this draft breed. While enthusiasts of the breed claim a separate origin that is strongly influenced by local aurochs, others are convinced that it has its origins among other local breeds and is closely related or descends from Barrosa and Mirandesa. So here is my take-on to this subject based on literature references, old photos and the phenotype of Portuguese cattle breeds.
First off, Maronesa has traditionally been considered a crossbreed of Mirandesa and Barrosa because of historic evidence . It has been considered a mix population until it was categorized as a separate breed in 1835. A genetic study from 1998 found a genetic distance to other Portuguese breeds . However, another study from 1993 found it to be genetically intermediate between Barrosa and Mirandesa , which is in line with the historic evidence. Another study from 2004 found Maronesa to group closely with Barrosa .
The claim, however, that Maronesa has an isolated origin (even from from local aurochs) is not based on any genetic or archaeological evidence. Advocates of this scenario base it solely on the ground of physical traits plus the one study from 1998 that places Maronesa apart from other Portuguese breeds. The physical traits of Maronesa are not a good argument for an isolated origin. At one point, all domestic cattle had a very aurochs-like appearance since all of them descend from the aurochs. In cladistics you would say: you cannot base relationships on plesiomorphies. Furthermore, the aurochs-like morphology of Maronesa mainly concerns the coat colour scheme, the well-marked sexual dimorphism and the horn shape. While the dimorphism is indeed exceptionally good, you also find these traits in other breeds.
Looking at the external appearance, it also becomes apparent that Maronesa has striking similarities to Barrosa (and the closely related Cachena), Mirandesa and also Arouquesa – all of them are neighbouring breeds from the same region. The similarities concern body shape, horn shape and face shape. Actually, many Arouquesa in fact look like a lighter-coloured and slightly more bulldoggish version of Maronesa. Thus, the striking phenotypic similarities plus the geographic and genetic proximity of these breeds suggest a common origin for these breeds to me. Phenotypic similarities can be misleading in domestic animals, but those of these five cattle breeds look very diagnostic and when you look at retriever dog breeds, the Irish setter and spaniels, you would also suggest a common origin or mutual influence between those breeds based on their looks – and this is exactly what is documented in their breeding history.
Maronesa is slightly more aurochs-like than the others because of its colour – the colour is way darker than in the other breeds, making primitive colour traits like the eel stripe or sexual dichromatism more visible in Maronesa than in others. But this can be caused by only one or two alleles alone, so the difference is not that considerable.
However, the darker colour would be an argument against a hybrid origin of Mirandesa and Barrosa for Maronesa: it is coloured darker than both of its alleged parent breeds. Also, the morphology of both Barrosa and Mirandesa is way more over-bred than in Maronesa. Thus, Maronesa seems to be more primitive and therefore cannot descend from two more derived breeds. But you have consider the origin date for Maronesa: it has been considered a separate breed since 1835, thus the origins of this breed must date back at least to the first half of the 19thcentury. All of the breeds were less-derived than today. There is a photo of old Barrosa in black and white where you can clearly see that Barrosa was way less derived than today (the individual in the front seems to be a steer). This goes for the colour (the steer seems to have a rather dark colour) as much as for body shape and skull shape. This, on the other hand, makes it credible again that Maronesa is indeed a crossbreed of Barrosa and Mirandesa.
And even if it does not directly descend from a mix of those two breeds, I think it is very likely that the breeds Maronesa, Barrosa/Cachena, Mirandesa and Arouquesa share a common origin from the same region of Portugal somewhere in around 1800. The phenotypic similarities and the geographic proximity are striking and there is also genetic evidence backing it up.
Thus, the scenario of Maronesa being an isolated relict breed that is somehow more closely tied to the aurochs than other Portuguese breeds is romantic and tempting looking at its colour and horns, but evidence suggests otherwise. And personally, I consider the similarities between aurochs and Lidia more deep-going than in Maronesa (see here or here).
 Marleen Felius: Cattle breeds: An Encyclopedia. 2005.
 Fernandez, Iglesias & Sanchez: Genetic variability and phylogenetic relationships between ten cattle breeds from Galicia and the north of Portugal. 1998
 Porter, Alderson, Hall, Sponenberg: Mason’s world encyclopedia of livestock breeds and breeding. 2016.
 Iannuzzi & Figueiredo: Frequency and distribution of rob (1;29) in three Portuguese cattle breeds. 1993
 Mateus et al.: Genetic diversity and differentiation in Portuguese cattle breeds using microsatellites. 2004