The Dog Kind

This would have been great for studying purposes for the Biology exam this afternoon. Not because there were any dogs in it (or Gods for that matter), but some of the general concepts are quite applicable to the questions in the Describe genetic variation and change paper. Once the creationism is removed, of course – I live in a civilised country, you know…

Anyway, the article title is How Did Wolves Become Dogs? I wonder…
A hunter with some beagles, 1885

From the tiny Chihuahua to the massive mastiff, the over 200 breeds of domesticated dogs come in a wide variety of different body sizes and proportions, hair lengths and textures, and demeanors. Evolution asserts that animals change through a gradual accumulation of mutations. But evidence shows that the wolf-to-dog transition occurred rapidly, according to pre-designed genetic potential and not mutations.

Already we have a straw man. The domestication and artificial selection of the Grey Wolf was more a process of selecting among pre-existing variation than relying on the production of new variation. Nobody thinks that wolves became dogs via evolution and natural selection – but instead it was artificial selection that did it. Darwin knew this. I wouldn’t be at all surprised if the guy in the photo above knew it. You don’t need to wait even until level 2 biology to learn it. And I can only assume that Mr Thomas is perfectly aware of the inaccuracy of his opening paragraph.

That’s not to say that mutations don’t figure, but there’s a lot of variation to work with as it is.

Mark Derr, author of a new book titled How the Dog Became the Dog: From Wolves to Our Best Friends, discussed on National Public Radio’s program Fresh Air how human interaction may have domesticated wolves beginning in the Ice Age. Since dogs are smaller than wolves and have more varying proportions, coat colors, and other features, interviewer Dave Davies asked Derr, “So how could this association of wolves with humans lead to these physical changes?”

Derr replied:

Well, what happened was that you had populations of dog-wolves that became isolated from the greater wolf population and in doing so, they began to breed more closely—to inbreed as it were. And when you inbreed, you get genetic peculiarities that arise, and those peculiarities then begin to become part of the population…. In other words, a mutation will appear in a small population. If I don’t want it, what I do is kill the animals so that they don’t reproduce. If I do want it, I try to get them to reproduce.

So, according to Derr, a certain “peculiarity”—for example, a curly tail—first arises by mutation. This mutation and its resulting trait are supposedly then concentrated into a distinct dog lineage by breeding the dogs that have it.

The transcript to the interview is here. He does say that, but he isn’t exactly saying that all change has to come from mutations that have happened there and then. Certainly he’s not saying that you need extra mutations to tame the animals – that, at least, is clear from the full transcript. Nevertheless:

At first, this might sound reasonable, but a landmark study published in the journal Bioessays in 2009 told an entirely different story. Researchers artificially selected foxes for “tameability.” Foxes were certainly part of the originally created dog kind, having been known to interbreed with coyotes, for instance. The experiment, which utilized Russian fox fur farms, began “about 50 years ago” and has produced scores of fox generations thus far…[T]hey used approximately the top 10 percent of the tamest offspring as parents for each next generation for dozens of generations…They didn’t need thousands of years, just three generations. And at just the sixth generation, fox pups eagerly sought human contact, complete with wagging tails, “whining, whimpering, and licking in a dog-like manner.”

And amazingly, the tame foxes quickly acquired an array of traits shared by many domesticated mammals, showing that mutations were not involved. To show this, the authors compared the wild and domesticated horse, cow, sheep, pig, dog, and rabbit. The wild animals have similar and stable traits, including erect ears, straight tails, restricted breeding seasons, and uniform coat colors and body sizes. But the domesticated ones had such features as floppy ears, curled tails, spotted coat colors, variations in coat textures and lengths, variations in breeding time, and marked differences in skeletal size and proportion.

That may be the case, but Derr was more talking about things that “have some function of beauty or utility” which humans would then keep and breed – that quote from the section of Mr Thomas’ quote that has been replaced by ellipses. Note also that when his quote returns another question has been asked by the interviewer. Derr is also of the opinion that changes in skeletal size etc come from pre-existing mutation, like most things.

Surely, chance-based genetic mutations could never produce identical variations in so many different kinds of mammals. For this reason, the authors wrote, “Finally, it is difficult to interpret the changes in the domesticated foxes as a result of randomly arisen new mutations.”

Did they now? In fact, they said it because they didn’t think that the “identical” mutations could have occurred in so many different litters that they had to be pre-existing in foxes. Not that they found it puzzling that foxes also had such variations.

Instead, changes in gene regulation must have caused these trait variations

Or maybe changes in gene frequency from artificial selection?

That’s not evolution by mutation, but variation by design.

That’s…wrong in manyways, not least in that it’s a non sequitur.

Thus, according to this research, dogs could have become “man’s best friend” in three dog generations from a wolf ancestor simply by selective breeding in the recent past.

They could get close – but all the way?


I suppose I can expect a chemistry-related DpSU after the exam on Monday as well?

Advertisements

3 thoughts on “The Dog Kind

  1. As I am a non-biologist, two cents is about all you are going to get.

    In the normal course of events, mutations will occur in the fox population, these will be almost certainly detrimental, only in the very long term and in changing environmental conditions, will any mutation be beneficial. In the short term, almost every mutation will be weeded out of the population by natural selection. The effect is to keep foxes fox-like.

    In the process of domestication described, the genetically damaged are selected to survive. These are those that cannot catch their prey, cannot find a mate, cannot defend their litter, over weight, floppy eared, very long or very short legs. These are the losers suddenly promoted to winners.

    Having selected a failure, man then finds another damaged specimen to mate it with. The resultant downward spiral in the breed will be rapid.

    Meanwhile the wild specimens go from strength to strength.

    Thus, although there may be no difference in the mutation rate between the domesticated and the wild specimens. The wild are kept pure (probably a completely incorrect term biologically) by natural selection while the domesticated are positively encouraged to express their mutations. It is not surprising that animals in domestication show greater rates of variation.

    • I would say that that’s probably the case, and that the creationists even know it. I’ve seen arguemnts before along the lines that evolution is only capable of rooting out bad mutations, which is taking the situation to the extremes… (and contradicts other arguments of theres)

  2. Pingback: Mistakes Were Made – But Not By Us « Eye on the ICR

Thoughts?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s