Canine Coolness

Science Daily has an interesting article about mutations in dogs:

The wolf is the first animal that humans domesticated. Even though all dogs descend from the wolf, today dogs occur in more variants than any other mammal. These variations are not only the result of breeding, but also of the comfortable life dogs lead, a life that has entailed genetic changes. We might expect dogs to be genetically different from those of another breed, but we might also be led to believe that they are relatively similar within a single breed.
But in fact dogs of the same breed are genetically more different than we thought, according to Susanne Björnefeldt. She mentions the poodle as an example: it is genetically divided into five groups, although kennel clubs divide the poodle into four distinct groups.

The story is based on Björnefeldt’s Ph. D. dissertation (caution: loads very slowly), which is much more interesting than the Science Daily article makes it sound. Basically, Björnefeldt used MtDna, Y chromosome DNA, and autosomal microsatellites to look at several issues, among them being: the impact of domestication on the canine genome, the process by which breeds were created, and the comparison of methods used to estimate gene flow with methods derived from pedigree information. I’ll have more to say about this once I have finished reading it. In the meantime a couple of interesting things stand out. First:

By analyzing mitochondrial DNA (mtDNA) control region sequences from 140 dogs representing 67 breeds and 162 wolves representing 27 places around the world, Vilà et al. (1997) suggested that dogs originated more than 100 000 years ago. Four clades of dogs were found in the phylogenetic tree and the divergence time between dogs and wolves were based on a calculation of the time for the most recent common ancestor of clade I, the most diverse monophyletic group of dog sequences, and assuming that wolves and coyotes diverged at least one million years ago. Furthermore, indication of an episode of interbreeding between wolves and dogs was also found. [emphasis mine – afarensis] By comparing the dog sequences with wolves and additionally samples from 5 coyotes and 8 jackals, they also found support for the hypothesis that wolves are the ancestors of dogs.

Which made me think of the paper awhile back indicating there was some interbreeding between chimps and human ancestors after they split. Not being an expert on speciation, I am lead to wonder how common this is when critters speciate? Alternatively, could this be a methodological artifact in both studies? Comments (and/or references) would be greatly appreciated. Another interesting piece of information relates more directly to anthropology:

The earliest find of morphologically distinct domestic dogs were found from the Upper Paleolithic site Eliseevichi 1 (central Russia). The two complete dog craniums found are remains from adult dogs resembling Siberian huskies in shape and have been dated to 13 000-17 000 years ago, based on 14C (Sablin and Khlopachev 2002). The earliest evidence of the close association between dog and human, on the other hand, is dated 10 000-12 000 years ago. The finding corresponds to a burial of an elderly person, with the left hand placed on the thorax of a 4-5 month old puppy … This was found in a limestone tomb in Ein Mallaha, Israel (Davis and Valla 1978).

I would love to see a picture of that, wouldn’t you? Okay, you have talked me into it:
Dog.JPG(picture from the link above).

2 Responses

  1. Not being an expert on speciation, I am lead to wonder how common this is when critters speciate?
    Well, the two populations aren’t completely isolated from each other even today, and in the past crosses between them would have been even more frequent. I would have been really suprised (and extremely suspicious) if the study hadn’t found interbreeding.
    Now, I’m not a scientist, just someone who finds this stuff fascinating, but it seems to me that the disappearance of wolf populations could be a problem. Wouldn’t the wolf populations most likely to have contributed most to dogs also be the ones most likely to have been recently eliminated? That is, the ones closest to human populations? Wouldn’t this create an appearance of greater antiquity in (ongoing) split?

  2. I’m a dog author who writes social history about our four-legged friend. The science sometimes throws me so I have a question: If some dog-like creature evolved from the wolf, independently of human domestication, in fact long prior to this than previously thought, how did it change PHYSICALLY before we started breeding it in isolation? i.e., the shape of the skull, length of muzzle, spacing of teeth — the neotenous features: Were they already beginning to take shape prior to domestication? What did these early wild dogs look like?
    Any thoughts much appreciated.

Comments are closed.

%d bloggers like this: