How and when did some European languages acquire retroflex d and t?

Question

It seems the retroflex d and t are present in some Germanic languages but not in most Romance, Slavic, and other IE languages.

I know that it occurs in IE languages of Asia, like Sanskrit, Pashto, and north Indian languages, (but not Persian), which could be explained as contact with people having these sounds in their language, but my focus is specifically on Europe.

Has there been any explanation given why it occurs in Germanic but not others?

PS: I am a rank amateur in linguistics, so I have used "some" and 'most' just to be on safer side.

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EDIT: I am a bit embarrassed that I mistook the alveolar stops t and d to be the retroflex ones; to me they sounded the same. It appears that only Norwegian and Swedish have them, as opposed to English, German and Dutch that I had listed in the original question. However, this information won't affect my interest in the topic. I have updated the question accordingly.

Answer 1

The only Germanic languages with retroflex consonants are Norwegian and Swedish (where it is a dialect feature -- not found in e.g. Bergen Norwegian where <r> is uvular). The origin appears to be <r>, reflected in the spelling, where [kɑʈʈ] "map" is spelled <kart> and [kɑtt] "cat" is spelled <katt>. Assuming the facts on Kristofferson's The phonology of Norwegian, ɽ is "more phonemic", and can be traced back in some contexts to earlier rd clusters in Old Norse that were simplified to [ɽ]. The retroflex flap also appears (depending on dialect) as a variant of /l/ after back vowels. There is a poorly-understood connection in a number of languages between preceding vowel backness and the r, l distinction (though one can either find the pattern [il, ur] or [ir, ul]).

In some dialects of American English, there is a coarticulatory process where in an onset cluster with <t,d> causes some retraction of the stop, which many people think sounds like [tʃ]. The actual quality of <r> in American English is fairly variable, but under a liberal interpretation of what "retroflex" means, one could say that <r> is a retroflex glide, in which case one could also say that /t,d/ also become phonetically retroflex.

Actually, many people say that Russian /ʃ, ʒ/ is retroflex and Polish has them too. Retroflex consonants are said to exist in dialects of Italian. All in all, these are probably natural phonetic developments that just happened to make it on the map of linguistic documentation in these languages. Basque and (dialects of) peninsular Spanish have what are usually termed apico-alveolars, which could be lumped together with retroflex consonants. It turns out that "retroflex" is not such a unified phonetic thing, so Indic and Dravidian languages differ in the values of the "retroflex" consonants.

Answer 2

There are two different things to consider:

Contrast between dental and retroflex d's and t's: Such a contrast has developped in the Indic subbranch of the Indoarian languages, probably due to contact with Dravidian (or Austronesian or Sino-Tibetan or other [e.g., Burushaski]) languages. It also occurs in the Sicilian dialect and in Norwegian and Swedish (in both cases due to internal development of the respective languages).

Quality of the d's and t's: Speakers of Indic languages hear the English d's and t's as retroflex and borrow them into loanwords as such. Portuguese d's and t's are borrowed as dental sounds in loanwords. I don't know the reason for this phenomenon.

Answer 3

I came across this question and wanted to give this input that might interest you. Even for Indic (Indo-Aryan) languages, the debate whether development of retroflex sounds was due to contact with Dravidian or an internal development is still open. The internal development account claims that the palato-alveolar sibilant underwent a context-free change to a retroflex sibilant. This introduced the retroflex manner feature, leading to the development of the stop series. My intuition is that the contact-based account makes more sense since there are other features (such as affixal conjunction, quotative complementizer) whose timeline matches with the retroflex sounds.

Answer 4

/ll/ > /ɖː/ in several Italian dialects (and, under Calabrian influence, in Calabrian Greek): https://en.wikipedia.org/wiki/Sicilian_language

ḌḌ— The -ll- sound (in words of Latin origin, for example) manifests itself in Sicilian as a voiced retroflex stop with the tip of the tongue curled up and back, a sound rare in the Romance languages. [...] The sound itself is not /d/ but rather [ɖ]. For example, the Italian word bello [ˈbɛllo] is beḍḍu [ˈbɛɖʊ] in Sicilian. This sound [ɖ] also evolved from Latin -ll- in Sardinian, to an extent in Asturian, elsewhere in Southern Italy, and in many northwestern Tuscan dialects.

(Southern Calabrian is a branch of Sicilian.)

So it does in fact happen in Romance; and in fact, it doesn't sound like retroflexes are that much more common in Germanic than in Romance. As for why some language features occur more in one language family than in others, it can be any of (a) areal diffusion (hence Calabrian Greek); (b) common inheritance; (c) coincidence.