…don’t forget that it takes 4-5,000 years to develop from the first consonant to the first sentence…
This is not so and anyway, all proto-languages came from prior proto-languages. Also, I have seen new languages emerge in the past 50-75 years. There is one in Spain in particular called Eonavian/Ibino. The older generation can still understand the language it broke off from, Galician, but the younger people cannot, so it’s a new language.
Where were the (climatic, civilizational, and all other) conditions for its development?
You don’t need any for a new language to develop.
Half of the Serbs have genetics found in Lepenski Vir/Vinca more than 10,000 years ago. Their DNA is the only group originated in Europe. That means they didn’t come from anywhere. What language did they speak then (e.g. 2,000 BC)? Alinei says that their language has continuity from the Paleolithic to today.
Everybody came from somewhere.
Well, that’s nice that a lot of Serbs were some of the original Europeans taken over by the Indo-Europeans. Also Basques have an original lineage too going back 10,000 years. As do Sardinians. And the Sami. The Sami are actually considered the oldest extant ethnic group in Europe.
Alinei is wrong. The only language that has continuity from that time (possibly) is Basque. Serbo-Croatian itself doesn’t even go back very far. It’s not that far apart from its neighbors.
I believe that prior to adopting a Slavic language, the Serbs and others in that area were speaking an Iranian language. An Iranian group had settled in that area at that time, although their culture and even existence is poorly understood. Apparently Serbs and the other Slavs just abandoned their previous language and took up Slavic.
If the so-called Slavic languages are 1500-2000 years old, from which language did they develop?
It was called proto-Slavic and Serbo-Croatian is not even the oldest language of them. The oldest are Rup in the Bulgarian mountains and Croatian languages spoken on the Croatian islands.
On what basis is the similarity of languages possible in, for example, Slovenia and somewhere beyond the Urals to Japan?
Slavic languages are no more similar to languages of the Urals and Japan than any other Indo-European language. Their parent language, IE, is related to Japanese and Finno-Ugric languages in the Urals, but only at a very deep level.
From which language did Sanskrit originate, and how do you explain its most remarkable similarity with the Serbian language?
There is not much of a similarity with Serbian other than, yes, there is a relationship with Slavic, but they’re both IE anyway. Sanskrit came from Proto-Indo-Iranian, spoken at the southern end of the Urals 4,500 YBP.
Where did Slavic languages originate?
A lot of people trace it to Eastern Germany and Western Poland. There are also some very ancient Slavic languages from the Bulgarian mountains and the Croatian islands. The most ancient Slavic languages are from there.