What Makes a Wolf a Wolf?

Have you ever looked around and wondered how so many different animals can all be related? In fact, scientists believe that all animals—and all forms of life—share a common ancestor. Gray wolves are only one out of billions of different species that live or used to live on the earth.

Although there are many different types of animals, most of the ones that you will be familiar with belong to the smaller group of vertebrates: animals with a true backbone.

Wolf Evolutionary Tree #1

Gray wolves are part of the order Carnivora, which is grouped largely based on their predatory diet habits. Carnivora consists of over 260 species, including dogs, cats, bears, foxes, skunks, and raccoons. They all have long, pointed teeth and sharp claws used to attack their prey. They are also fairly intelligent animals with highly developed brains.

Wolf Evolutionary Tree #2


Wolves belong to the family Canidae and are most closely related to domestic dogs, foxes, coyotes, dingoes, lycaons, and jackals. There are 14 total living subgroups of Canidae, and they are often referred to as canids. A derived trait for canids is that they have 42 teeth, although bears also share this characteristic. There are, however, other distinguishing features between canids and bears. Canids tend to have long tails, walk on their toes, and have four toes to each hind foot, while bears have short tails, walk on their soles, and have 5 toes to each hind foot.

Wolf Evolutionary Tree #3

 

The gray wolf looks very similar to other canids, so differentiating species isn’t always straightforward. Throughout its evolution, the wolf has been increasing in size, so wolves tend to have a larger body that most other canids. Furthermore, after collecting skull measurements from the wolf, scientists have found that it has a broader snout and wider nose pad than its other close relatives.

The Gray Wolf: Evolutionary History and the Fossil Record

How old is the Gray Wolf (Canis lupus)? This is a more difficult question than you may at first think!

We believe that the some of the early ancestors of the Gray Wolf were a group of generalized carnivores named the creodonts that first walked the northern hemisphere of the earth between 100 and 120 million years ago. About 55 million years ago, the creodonts gave rise to the carnassials, a group of wolf-like animals that had specialized jaws for eating meat. One member of this family, Miacis, is thought to be the ancestor for all present-day wolves, dogs, weasels, bears, and raccoons.

Miacis branched into a number of species by 30 to 40 million years ago, giving rise to a more recent ancestor of modern wolves. Cynodicits, however, was much smaller than the wolf of today, with shortened legs and a flexible body.  Between 15 and 30 million years ago, Cynodictis split into Cynodesmus and Tomarctus to give yield to wolf-like animals with longer legs, more compact feet, a shortened tail, and a smaller big toe (Mech 1972).

When did the wolf become a wolf? Somewhere between 4.5 and 9 million years ago during the Miocene, the recent ancestors of wolves split off from the ancestors of foxes. By 1.8 million years ago, wolves in North America had split from coyotes, and looked very much like they still do today. Just think of this: when you look at a wolf, you are in a way looking at an animal that is 2 million years old!

How do we know this? Of course, there were no people alive 120 million years ago to help us out. So we use the fossil record, which means that we look for evidence of the ancestors of wolves through bones or other remains that have been preserved by the earth over time.

For wolves, the evidence is pretty convincing, although it is incomplete.  Scientists have tracked changes in skull size and shape, limb length, the evolution of sharp teeth for tearing meat, and evidence of changes in wolf population and habitat distribution over very long periods of time. In fact, researchers’ use of the fossil record has led them to believe that North American wolves crossed the land bridge to Eurasia and established themselves there 130 to 300 million years ago to evolve into Canis lupus before returning to North America! The wolf species that never left North America became different from those who had left and then returned (Boitani & Mech 2003).

The sheer diversity of canids is amazing. Some of them are more closely related than others, but all share an amazing evolutionary history that might even make you howl!


Information compiled by: Carolyn Loeb, Megan Crawley, and Sabrina Orlins