Nature of transitional species

Alright, we have a lovely post for you this evening.  Sit down, get comfy, and prepare to be amazed.

Let's put some context in here, shall we?

@chridgriebe @SecularScarlet @buzzet270 Fine, understand anything but don't teach transitional evolution to kids. Never been proven.

— Lt. King (@FreeAmerican100) October 22, 2015

So, let's address this in two parts.

PART ONE

Part one is pretty direct.  Evolution has tons of evidence (read:proof) available for anyone willing to spend the time to learn about it.  This is true of most subjects, actually.  One cannot simply claim something is unproven just because someone doesn't like it.  Since this is a factual inaccuracy (I won't call it a lie yet), we shall move on.  I think you will find that part two actually gives some fairly compelling evidence for transitional species.

PART B

Alright, let's get down to science.  Transitional species are a thing, and I'm going to provide two examples here.

Ring Species

Ring species are a group of animals (for our purposes) who exhibit a very interesting trait.  This trait is that there are a given set of species who can interbreed, but not fully.  Let's examine this a bit closer. 

The most common example, and the one we'll use here, is that of the various salamanders that inhabit the greater California area.  There are approximately seven distinct species.  Each lives in a given area, and typically not outside of it.  Species one and two, for example, have habitats which overlap.  Species two and three have the same, but species three is never found in species one's habitat.  Species three and four follow the same pattern, and so forth, for all seven species.

This gives us our first example of a ring species.  Species one and two can interbreed very easily, and do so quite frequently.  Species two and three can do the same.  Same with three and four, and each consecutive pair down the line.  However, we have an interesting observation.  Species one and seven never interact.  When scientists tried to mate them, it was impossible.  We can show a large trail of interbreeding between these very similar species of salamanders, but the salamanders at either end cannot breed together.  Species that are closer together can have success sometimes, and species that are directly in contact can breed nearly as successfully as a species with itself.  

This is one of the simplest ways to explain transitional species.  In another few thousand (perhaps million) years, these will all eventually be distinct species.  Most certainly, one or two of the 'links' in this chain will die off, or eventually two near species will become so distinct that they will be like far links in the chain.  This brings us to our second example, an example that's a bit further down that evolutionary line.

Equine Evolution

This one is a bit more interesting, from a short-term observation.  Horses and Donkeys present us their story here.  

Horses and Donkeys are approximately as unique from one another as perhaps neighboring (or perhaps a link or two separate) salamander species.  Horses and donkeys can produce offspring, which we typically call mules or hinnys, depending on if the male or female parent was a horse.  Occasionally, a female bred this way will be able to have offspring, but this is a rather rare occurrence.  

Horses and donkeys were at one time a much more similar species, and even farther back in time would have been literally the same species.  This is shown quite clearly by the fact that they can still mate.  This is almost as easy to produce as a either a horse or donkey, but the offspring are typical not able to increase progeny (have offspring).  In this way, we can see a species transitioning right now.  There was a time when their offspring would have been equally valid, and equally as likely to produce offspring.  This time is slowly passing, as it typically does for most species that slowly split. 

Humans and other primates shared this fate, although a considerably longer time ago.  Even the split between mammals and marsupials, for example, would have started in a fashion like this.  It's entirely possible that a viable strain of mules could arise naturally, but at this point it's very unlikely indeed.  Selection pressures against it are too great at this point.  Eventually, there will come a time when horses and donkeys will not be able to breed for mules.  This is still quite a way off, perhaps several tens of thousands of years, much as it's taken tens of thousands of years of domestication to create the two distinct species, for example.

CONCLUSION

That brings us to the fun part.  Remember, evolution is real, whether you like it or not.  Although, why wouldn't you like evolution?  Without it, you wouldn't have adorable cats, mules, or, well, any species.  

This isn't imgur, but enjoy these pictures, cat tax and all!