Latin used to be what english is now, probably even more prolific...or maybe I'm speaking too soon. Its Ironic, Romans invaded the Earth, yet instead of speaking Italian or vanacular, they prefered Latin. Further suggestive to the fact that Romans annihalated themselves.
Uh, I don't know where to begin. How about this way...
The language in which "Beowulf" was written is called Anglo-Saxon, because it was the Germanic language or dialect (distinction is a little fuzzy in tribal cultures) that was brought over by the Angles and Saxons. Sensible enough, right? However, when I was a kid it was called Old English, because it was the language spoken in England during the era before the Norman invasion. It is the direct ancestor of Middle English, the language of England post-1066.
So, let's look for an analogy. The language of the Caesars is called Latin because it was the Indo-European language of the tribe that can be identified with a place called Latium. It is the language that was spoken in Rome, and then later in the Roman Empire as the Romans spread throughout most of Europe and some nearby lands, up until roughly 600-700CE, when the Western Roman Empire collapsed. However... it could just as sensibly be called Old Italian. It is the direct ancestor of the languages of the various Italian city-states when they were first recorded around that time. Unlike Anglo-Saxon, Latin spawned a whole family of languages from Romanian to French to Portuguese, but all of those examples bear heavy outside influences (Slavic, Germanic and Arabic, respectively), whereas even the Italian of today is rather pure in its Latin heritage. (Much closer than English, with its dumpload of French and Latin words, is to its Germanic roots, for example.)
There's no really good reason not to refer to Latin as Old Italian, or to Italian as Modern Latin. (As we refer to Modern Greek and Modern Hebrew.) The point is: there was never a time when both Latin and Italian were spoken, because they are time-lapse snapshots of
the same language. So to say that the Romans did not spread Italian is a meaningless sentence.
It's actually rather difficult to speak of "Italian" up until very recently. Florence, Rome, Sicily and each of the other principal medieval city-states had its own language. There was a lot of travel and commerce among them so they influenced each other, but they remained distinct. Around the end of the 19th century the nation pulled together politically and decided to pull its language together at the same time. I believe it was the Florentine dialect, not Roman, that has the greatest influence in Modern Italian. There's another thread on this forum with a URL to a nice article about the history of Italian.
Or to put it more succinctly as John did:

There was no Italian back then
Most taxonomic classifications for all life on Earth are named with Latin words, but it's not really a rule. Just a convention. For example, I might talk about a cougar, and you'd think "What? What's a cougar?"
BTW, you forgot that in much of the South they're called "panthers."
To avoid this, everyone would just talk about Puma concolor.
You're kidding? They keep breaking up what used to be the genus Felis. Even after lions and tigers got moved to Panthera, mountain lions were still called Felis concolor. I suppose this means that despite the greatest efforts of dedicated scientists, no one has succeeded in getting a housecat to breed with a cougar?
Latin genus/species names are always written in Latin in all Western languages.
Yes but perhaps we should make clear that in many cases that is simply Latin
syntax, not true historical Latin words from the tongue of Caesar. The most common bacteria in your intestine, the usual culprit in food poisoning, is Escheria coli. Escher is just the name of the scientist who discovered it. Poinsettia, Wistaria, the names of many genera are a history book of botanists, with their names taking Latin grammatical suffixes.
I call them the Southern Grizzly, Northern Grizzly, Northeast Grizzly and North Northeast Grizzly.
Start from the foundation that "grizzly bear" is not capitalized. English names of species are not, unless they contain a proper name like "Oregon junco," "Przewalski's horse" or "African elephant." Therefore there's never a reason to capitalize "grizzly." Northern and southern? Regions are not
usually capitalized. Exceptions include the Civil War and its aftermath: Southern politics maybe, but not southern grizzlies. Historical events: the Northwest Passage, but not northwest grizzlies. Regions that have taken on identities of their own: Northern California and Northern Virginia, but not northern Delaware and not northern grizzlies.
Stick with lower case unless one of the words comes with its own capital, and even then be skeptical.