Friday, September 03, 2010

Long Overdue Book Review: Dogs: Their Fossil Relatives & Evolutionary History

Dogs: Their Fossil Relatives & Evolutionary History is an aptly-titled book from Columbia University Press about the evolution of Man's Best Friend by Xiaoming Wang & Richard Tedford, with illustrations by the incomparable Mauricio Anton. First, I'll say this: if you're a paleo-artist, you need this book just for the illustrations. You will be continually inspired by Anton's photorealistic work. Along with Carl Buell, Mauricio is the most talented prehistoric mammal artist working today. His lavish pencil drawings dot almost every page, and the plates in the center of the book feature his full-color paintings which are a sight to behold.

Aside from the art, Dogs doubles as a handy and very educational reference guide for many aspects of canine evolutionary biology. The authors examine every aspects of dogs, including dog-like carnivorans that are not dogs, like creodonts and borhyaenas. They discuss what makes a dog a dog, and what makes a dog a carnivoran. These are things I never knew. I was especially fascinated to learn that one of the key distinctions between the dog (Canidae), bear (Arctoidea) and cat (Aeluroidea) branches of the Carnivora is the structure of the auditory bulla--the dome-shaped bones at the base of the skull that cover and protect the inner ear. Another interesting factoid is that the common ancestor of cats and dogs probably had retractable claws!

The authors dive into the evolutionary history of dogs and include discussions on just about every genus and species that popped up since the Eocene. The first dogs were fox-sized animals that were actually pretty dog-like, but with long tails and relatively short limbs. However, they quickly diversified and many dogs developed bone-crunching jaws and robust bodies while others stayed lean. It's clear that canids experienced a fast and impressive radiation early in their evolutionary history. The most impressive fossil dogs are perhaps the borophagines--big, short-skulled, tough-jawed bone-crunchers. With domed foreheads and short jaws, these big canids bear some resemblance to small dog breeds today. A less-derived borophagine, Aelurodon, had proportions more suited to a cat or bear than a dog.

The only "mistake" I see is that Wang & Tedford constantly discuss a direct line of decent between any one species or genus and another, as if dog evolution has been essentially anagenetic throughout its history, but that can't be true. This is a common complaint I have with books discussing the evolutionary history of mammals generally, but it's very noticable here.

The authors then discuss, in impressive detail, how dogs work in comparison to other modern carnivores like bears, cats, and hyaenas. Differences in the teeth, the skulls, the senses, and the musculature of the head and neck are are gloriously discussed and illustrated, which gives great insight into how all of these different carnivores can operate in their own spheres without competition. Unfortunately, the authors don't really look at postcranial anatomy (that could probably be its own book).

Happily, the book does look generally at dog behavior and society. Sexual dimorphism, scavenging, and pack hunting are all discussed and compared to cats and hyaenas. It's a relatively brief look, but it's appreciated nonetheless. Better, perhaps, is the discussion on how canids filled their environmental niches throughout their evolution as the world changed. Canids didn't reach their peak of diversity until the late Oligocene, for example, an event which may have contributed to or benefitted from the decline of more archaic predators like hyaenodonts. Basal hesperocyonine dogs began to dwindle in number by the middle of the Miocene but were readily replaced by borophagines, which exploded in diversity and dominated until the late Miocene/early Pliocene, at which point the world was changing, and modern canines took their turn.

Interestingly, modern canids (including wolves) did not really diversify until the Pleistocene Ice Age. The largest (but exinct) modern canine, Canis dirus, was the top predator among Ice Age megafauna. Modern dogs may have rose to dominance because of their flexible diet. While most dogs are "strictly" carnivorous, none will turn down tasty vegetable matter (just ask my corgi) or, in one case (Cerdocyon), crabs. Wang & Tedford wrap things up with a lively discussion of the history and debate of dog domestication, noting that dogs were the first animals to be domesticated by humans. But were dogs domesticated by humans, or did they domesticate themselves? This final chapter doesn't necessarily answer that question, but it does offer intruiging insight.

Dogs: Their Fossil Relatives & Evolutionary History was originally published in hardback in 2008, but came out in paperback earlier this year. It's a fantastic read, and as I said, worth the price of admission purely for the incredible art. But hey, you might learn something too, and this book of course provides an excellent companion piece to The Big Cats. They're sitting next to each other on my shelf, though I wish I had a hardcover copy of that feline book...

Apologies to Meredith Howard for not doing this sooner!


Will Baird said...

It was a good book. Now we need bears and their fossil relatives...

Brian said...

Well, it is a very good book of course. However, I did consider it a little underwhelming compared to The Big Cats at first. Like you said, the direct ancestor-descendant links proposed for various genera and species with an air of 'obviousness' around it, seemed a bit simplistic to my tastes.
Also, there's the fact that I find the treatment of living kinds of dogs rather meager. For example, *Cuon* and *Lycaon* are hardly mentioned and little is said about their background. *Atelocyon* (and possibly some other Neotropical genera, can't remember exactly) are not mentioned at all! I also found the absence of *Canis siemeniensis* in the text a bit disappointing.
I can see how the authors preferred to restrict themselves to their 'main line' of dog evolution but I think a title that strives to document said history should at least properly discuss all living species.
That being said, I do think it's a great book though I consider The Big Cats to be superior.