Alrighty, boys and girls, today we’re going to be talking about the convergent evolution of the North American wolf and the thylacine (aka, Tasmanian tiger, Tasmanian wolf).
Just as a little background for you, convergent evolution is when two unrelated and geographically and/or reproductively separated species both evolve to resemble each other. This type of evolution is behind such incidents as the rise of wings from different mechanisms (i.e. birds, bats, and insects) and, more famously, the strikingly similar eye anatomy of both cephalopods and mammals despite hundreds of millions of years worth of evolutionary separation.
Now, some info on the two animals we’re going to be looking at: first we’ll talk about thylacines. Aside from the fact that the last known thylacine died in captivity around the 1930′s, most important to note is that thylacines are, like all other native Australian mammals, marsupials. Marsupials are a branch of mammals whose young are born exceptionally early and then develop in the mother’s pouch. This lineage of mammals diverged from the rest of the therians about 110 million years ago; thus, thylacines had quite a separation from our modern day wolf. I’m going to guess that you’re most familiar with red wolves and timber wolves–those that inhabit the US.
So now we have established some basic information: the definition of convergent evolution and the background behind the two animals I want to mention who convergently evolved. Now, I want to show you the skeletons of the animals.
This is our modern day wolf.
This is a thylacine.
There are some notable differences in the two. First is the arching of the thylacine’s spine while the wolf’s back is more level. Next is the elongation of the wolf skull as compared to the thylacine. This creates a more gently sloped appearance to the back of the thylacine’s head and neck when the animal moves (however, the skulls of dogs and thylacines are so difficult to tell apart that even experts must sometimes rely on a standard marsupial trait {two holes in the palate} to differentiate between the two.) The pelvis in the wolf is also much larger, of course referring to the fact that wolf young are born much further along in development than thylacines. Also, the thylacine’s scapula sits higher on the spine than the wolf’s does. But all in all, these two animals are remarkably similar. They even both have 12 pairs of ribs and walk on digitigrade feet!
Now, given the behavior and ecological niche of these two species, it would make sense that they would have to have very similar builds. Both are/were apex predators in their respective habitats, and their body structures reflect that. Nature must have “guided” them to the perfect conformation.
The thing is, tt’s just amazing to think that, completely by chance, these two animals, separated by at least 110 million years of evolution, exceptionally unique lineages, and very different types of habitats, somehow ended up looking so much alike. Crazy. If I didn’t know better, I would have thought Someone designed them to look that way.
