I am in the beginning stages of thinking about learning both Ancient Greek and Latin. During my initial research, I have encountered some people saying that learning Latin first is what is commonly done, and that it is helpful when learning Ancient Greek. I have also read some people say that it makes no difference.
What are the benefits of learning Latin first as opposed to Ancient Greek, and vice versa? Are there any at all?
Learning Latin is (generally speaking*) easier than Greek; you don't need to learn a new alphabet, and if you know a little bit of Italian, French or Spanish, you might recognize some of the words. Even English has, because of the large influence of French, many words whose roots can be traced back to Latin.
Since it's easier, you're more likely to make significant progress and actually enjoy learning a new language, which is important. (Personally speaking, learning new languages quickly becomes addictive.) And in the meantime you'll be prepared for most of the peculiarities that classical languages have, so you'll have a head start when learning Greek.
Conversely, learning Greek first is harder, and you have a higher chance of developing a dislike for it.
*: of course, if your native language is Modern Greek, things are different
The best choice depends on various things, like your goals, the time available, your language background, the courses you could attend, and probably other factors that did not occur to me. I will give my answer with my reasoning, but it is up to you to decide whether that reasoning applies to you as well. I never was a full time student of classics; it was a minor subject. Therefore I did not have the capacity (in time or other resources) to pursue Latin and Greek the way some others do.
I found it best to learn Latin first. This had a number of benefits:
It helps keep the languages separate. I find myself confusing less vocabulary and grammar between languages if I first get a solid grip on one before moving to the other.
Comparison to other languages helps learning. I found it much easier to compare Greek to Latin when I actually knew Latin well. I don't think learning the two side by side would have lead to the same results with me.
Latin morphology is simpler. Latin declension and conjugation is straightforward and there is no need to learn rules of any sound changes (like vowel contractions) at first. Once you know the nominative and genitive forms and the gender of a noun, you can almost surely decline it right. Figuring out how amans and cecini correspond to amantis and cano helps understand Latin better and makes Greek morphology easier to approach.
Latin courses were better available. In high school no Greek was offered (and now my old school no longer offers Latin either). I could have easily continued to a master's degree and even further in Latin if I chose so, but only very elementary courses of Greek were offered.
Eventually I found myself liking Latin much more than Greek, so I did not pursue Greek much further. If I had committed to learning them side by side, perhaps my declining interest in Greek would have hurt my interest in Latin.
My suggestion is to study Greek and Latin together, calmly, step-by-step, in order to see the differences and similarities between the two grammars and their usual constructs. This is also the pedagogical system used in Classic high-schools in Italy.
Unfortunately I must disagree with Joonas' last point. It depends from person to person, of course, but I find it reasonable to like more Latin than Greek at a certain point, because the latter has more complex and variable structures than the first. When translating Latin becomes more habitual, and learning Greek is more difficult, it is natural to suffer a little approaching Greek studies.
Instead studying them both from the beginning is challenging and really interesting. There are parallels between the two languages which are not to be ignored. And when you are tired of studying a language, well, you can switch to the other!
Finally, both Latin and Greek's authors offer wonderful perspectives upon the world, and comparing ideas and histories between them can result in a beautiful enrichment.
There is a passage in the novel "The Last Samurai" about this -- the protagonist, an eight-year-old, is studying a Greek textbook on the bus. People come by and comment. "That'll help him learn English better." "That'll develop his ability with semantic structures." "That's always great for college admissions."
NO ONE says: "Greek is such a beautiful language, so rewarding to the mind that engages with it."
NO ONE says: "There is so much wonderful literature in Greek."
So that might be one thing to think about first--is learning just instrumental? Why learn Latin OR Ancient Greek--because they're there? Like climbing Everest? Why not learn Hebrew? Why not botany? Why not theoretical physics?
I'm not saying learning these languages is not a good idea. I started Latin when I was nine and I loved every minute of it--the vocabulary, so close to that of English, along with the grammar, so different, so crisp. But I never really read all that much in Latin that I found very good. Pliny's letters were cool. The Aeneid is schlock--Virgil copied Homer. So if you want to read amazing Western epic poetry, Greek. Julius Caesar is dull and Cicero is more dull. Catullus is wonderfully perverted but one isn't allowed to read him until college.
And much as I loved studying Latin and now love having learned it, and having all those beautiful interlocking verbal structures deep in my head, I am aware that I did spend my boyhood--when it was easiest to learn foreign languages--learning a DEAD language. I started with Spanish at 14, five years later than Latin, and I'll never know Spanish as deeply and readily as I know Latin. So maybe you might take that into consideration--wouldn't it be wonderful to know Japanese or Mandarin or Russian or Spanish or Navajo or Swahili as well as you know English?
While most of the answer to this question is subjective, I'd answer analoguous to @shootforthemoon, except that it's conceptually nigh impossibly to start learning both literally at the same time,
When you say:
"During my initial research, I have encountered some people saying ..."
It does not appear as if you had done any research on the language itself. Learning the history and linguistic facts can work well in tanndem, and the history can be hardly separated at all. I'm sure you have however common knowledge, not the least because, as the prior answers hinted at, similarities to Grecko-Roman culture can be found in many layers of our own, including language.
An intensive introduction is of course more efficient if focused on one coherent language. Which one that should be depends on the value that you expect, which, yes, depends on the difficulty, but an introduction is easy, pretty much by definition. I mean, you don't expect to become proficient immediately. It should get you far enough to recognize enough differences; it should establish coherence.
After that, you never stop learning so you eventually will learn both in tandem, unless you learn just one of them.
You might as well ask on which one you should focus. But that depends on your use case, what you want to read, or whom you want to write.
Since other have already answerd in favour of Latin, I will try to argue for Greek, or generally the less favoured language: It might make sense to start with the less interesting one, to save the best for last, as they say. That might as well be Latin.
There's a bit of a circular argument, when those proficient in Latin but not so much in Greek described Latin as easier, if that's due to the longer Latin tradition in education. I mean, yeah, inflection patterns might be coherent in Latin, but that's only relevant because Latin has so much of it. I'm not sure that's exactly easier. Also, many loanwords changed drastically, so that's not an argument, and it might even be a detrimental source of confusion.
Nevertheless, I can't say they were quite wrong, it may be useful to broaden ones horizont incrementally, if you try to approach any second language as a rather weird dialect of your native tongue.
Starting learn both at once, say with a trilingual dictionary, a few common grammatical patterns and cognate sets and what else, that would be a project of its own. I don't think that's commonly done. It usually works the other way around, learning both languages to reconstruct the common ancestor, because too little is know of the history to use as a basis for language education.
