Both Baltic languages sounds totally different.
As my cousin Estonian remarked, Latvian has experienced strong Finnic influence. Great parts of Northern Latvia were inhabited by Balto-Finnic tribes whose vernacular developed later to Livonian and Estonian. Livonians have become almost totally assimilated by Latvians but the Livonian (Liv) language has left remarkable traces in Latvian, e.g. stress almost always on the first syllable, as in Finno-Ugric languages. This has again led to reduction of vowels in later syllables, so Latvian words are often shorter than their Lithuanian counterparts (labs - labas = good).
Livonian continues to live in Latvian. "I have a book" is in Latvian "Man ir gramata" (literally: 'By-me is book'), in Lithuanian: "Ash turiu knyga" (is this right, Vytenis?) This is a typical Indo-European expression (literally 'I have book). 'I must go' is in Latvian 'Man vajag iet'. This is also due to the impact of Livonian. Livs would say: "Minnõn um vajag lädõ" ("By-me is need to go")
Yes, it is true. It may be that Latvian and Estonian were influenced to a greater degree by Finnic languages and by German. Lithuania was surrounded by Russian and Polish for most of the history (apart from that small part of the south-west which was under German domination). However, even now the eastern dialects like "aukstaiciu" and "dzuku" sound more slavic than "zemaiciu" (samogitian) in the west, which must sound more like germanic languages. Here is the map of major Lithuanian dialects
http://en.wikipedia.org/wiki/Image:Etnoregionai.png
Minnõn um vajag lädõ
HUngarian = Mennem kell
As for the theory that both baltic and slavic languages developed from the same common proto-language it is still the object of discussion and linguists disagree. The whole issue is too much politicized in my opinion. But even if they did not have a common proto-language, the fact that there were so many contacts between baltic and slavic peoples over many centuries may explain the phonetical closeness of Lithuanian and Russian or Polish as well as numerous slavic borrowings in Lithuania (both ancient and modern). So the closeness is hard to deny. Whether some politicians find it pleasant or not is another matter. However, significant differences exist too. Lithuanians are traditionally and culturally Roman catholic and they use and always used latin alphabet (even during Russian occupation periods) and Russians are cyrillic eastern orthodox, which is as different as white protestand americans are different from dark-skinned catholic hispanics... But then again, many other slavic nations like poles, slovaks or croats are both latin and catholic...
Vytenis your English sounds beautiful. Can you speak only Latvian and English?
Who reads your post would think that there are only mounds and megaliths down to Ireland. What about France, Portugal, Spain, Italy?
The Celts built up megaliths in Portugal as well and in Estremadura.
>>>Vytenis your English sounds beautiful. Can you speak only Latvian and English?
Thank you for the compliment :) Yes, I can speak Lithuanian, English, Russian and some German. Latvian is unfortunately not intelligible to me apart from some separate words or phrases...
I think Baltic languages are grouped together with the Slavic ones, in the
Baltoslavic group of Indoeuropean languages.