...continued from https://www.inaturalist.org/posts/56803-an-extinct-canid-canis-rubronegrus-hiding-in-plain-sight-in-the-domestic-dog-canis-familiaris-part-1#
I have just read Smith et al. (2017, https://www.publish.csiro.au/zo/zo17040), which contains important data and analyses.
Please note that the terms 'braininess' and 'EQ', as I use them in this Post, are not synonymous.
This is mainly because EQ (encephalisation quotient)
EQ in canids tends to complicate rather than to clarify the picture of relative braininess. This is because the domestic dog varies so much in body mass (according to breed) that the ancestral body mass is obscure.
Despite the above complications, Smith et al. (2017) found that
I have reshuffled the data in Smith et al. (2017) as follows, to list all those spp./breeds with body mass about 10 kg, in decreasing order of EQ:
How do we interpret the fact that EQ in various breeds of the domestic dog exceeds that in various like-size wild canids? Part of the answer is that EQ was originally conceived as a species-specific quotient.
When applied to breeds within a species, EQ becomes subject to interpretation because of the uncertainty of 'typical' body mass, as follows: EQ exaggerates braininess in small-bodied breeds, and understates braininess in large-bodied breeds.
I assume that the EQ corresponding with the 'real' species-specific EQ of the domestic dog is about 1.0, corresponding to body mass about 20 kg.
Please bear in mind that the point of Smith et al (2017) was the braininess of the dingo relative to the domestic dog; all wild canid spp. were ancillary to their study.
On the above basis, the following picture emerges from Smith et al. (2017).
The domestic dog (excluding the dingo) is less brainy than both the wolf and the Eurasian jackal (C. aureus). It is true that the difference is greater relative to the wolf than relative to the Eurasian jackal. However, relating this to the question of the real main wild ancestor of the domestic dog is rather subjective.
It seems likely that 'Canis rubronegrus' would likewise have been brainier than the domestic dog, based on the finding that all three extant wild spp. of Canis (wolf, coyote, and Eurasian jackal) are brainier than the domestic dog.
So, the data analysed by Smith et al. (2017) do not necessarily undermine the possibility that the domestic dog, with its anthropogenic decephalisation, was mainly derived from an extinct jackal-like (relatively omnivorous, non-gregarious) species rather than the specialised carnivore that is the wolf.
However, the data do suggest that my hypothetical ancestral species, 'Canis rubronegrus', was larger-bodied (about 20 kg) than extant jackals (about 10 kg).
The kelpie breed, with its wild-type conformation and colouration, has body mass 11-20 kg (https://www.perplexity.ai/search/What-is-the-ToObfrkBRw2sKkYuQVAdLg).
The wild ancestor must have been somewhat large-bodied, on average, than the kelpie, if we are to make sense of the EQ values of jackal-size (about 10 kg) breeds of the domestic dog.
In other words, I suggest that 'Canis rubronegrus' was jackal-like in diet and sociality, more than in body size. This would be consistent with Bergmann's rule (https://en.wikipedia.org/wiki/Bergmann%27s_rule), if the ancestral species lived at the northern limit of the vegetated landscape in the Ice Age.
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https://www.perplexity.ai/search/Body-mass-of-6.Q8sZ2QTw2b3WpjJbdyMA
DATA IN GITTLEMAN (1986, https://repository.si.edu/bitstream/handle/10088/4050/Gittleman1986a.pdf?isAllowed=y&sequence=1):
n = 10 for each species
The first value is body mass, the second is brain mass.
Canis lupus 33.11 kg 131.63 g
Canis latrans 10.49 kg 88.23 g
Canis aureus 8.76 kg 72.24 g
Lupulella adusta 11.25 kg 51.94 g
Lupulella mesomelas 7.69 kg 56.83 g
Lycaon pictus 21.98 kg 129.02 g
Cuon alpinus 17.64 kg 94.63 g
Lycaloplex culpaeus 7.32 kg 51.42 g
Speothos venaticus 5.99 kg 40.45 g
Chrysocyon brachyurus 23.10 kg 120.30 g
Atelocynus microtis 9.03 kg 62.18 g
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