Nothing but a hound dog...

...but that's a lot. Dogs on my mind this morning.

In my circle of canine friends and family, there's a German Shorthair Pointer, a Chihuahua, a Labrador Retriever, a pit bull, a Chinese Crested, and an assortment of other mutts. All very different, all loved. We're used to the diversity, of course, but it's still remarkable. In fact, the degree to which we've artificially shaped Canis familiaris over a fairly brief time period is usually part of my introduction to the power of selection. A new study in American Naturalist (referenced here at Science Daily but, for the life of me, I can't find in on the journal's home page) looks at the degree of diversity in domestic dogs by comparing skulls shapes with those of other members of the Order Carnivora. Not surprisingly, the authors found as much diversity within the dogs as they did within the rest of the Order as a whole. Not only that, but they found that the extremes of skull shape within dogs was greater than the extremes found between all other carnivores. A greater difference between a small pugnosed breed and a large, long-nosed variety, for example, than between cats and pinnipeds. The differences, of course, go far beyond skull shape. When we consider build, coat color and length, ear size and shape, etc., the degree of diversification within domestic dogs is pretty astonishing.

Think about that. Dogs are a fairly recent arrival on the evolutionary scene. There's debate about when they were first domesticated, although many experts put an estimate at around 15,000 years ago. However, most of the more than 300 currently recognized breeds have been developed over the last few hundred years. The diversity that we see today has been brought about within a few thousand generations by the application of a fairly strict regime of artificial selection - picking the traits that we like in a particular breed and avoiding the ones that we don't like. Nature may be a bit more sloppy - the big dog doesn't necessarily get to leave more offspring than the runt in a natural population - but it's had a lot more time to operate. Selection is a very, very powerful mechanism. Don't understimate it.

While I'm on the subject of dogs, best wishes to my favorite dobie. Feel better, big girl.