Did Portuguese gain or lose fricative allophones of /b, d, g/?

Question

Lenition of Voiced Stops

In Iberia, the three voiced stops /b/, /d/, and /g/ undergo lenition when they appear between vowels, producing fricative allophones:

• [b] → [β] for example, alfabeto, sílaba, receber
• [d] → [ð] for example: academia, cada, estados
• [g] → [ɣ] for example: vogais, artigo, chegar

This happens in Catalan, Spanish, Galician, and Portuguese. It does not, however, appear to occur in Brazil.

The Wikipedia article on Portuguese Phonology explains:

• In northern and central Portugal, the voiced stops /b/, /d/, /ɡ/ are usually lenited to fricatives [β], [ð], and [ɣ] respectively, except at the beginning of words, or after nasal vowels; a similar process occurs in Spanish.

The Portuguese version of that article says essentially the same thing:

• No norte e centro de Portugal, as plosivas sonoras /b/, /d/ e /g/ podem sofrer lenição e se transformarem nas fricativas [β], [ð], e [ɣ] respectivamente, exceto no início de palavras, ou depois de vogais nasais.

Do we know why Brazil and Portugal differ in this way? There is no such split in Iberian dialects of Spanish versus its American dialects: lenition happens anywhere Spanish is spoken. Similarly, all versions of Catalan have it. But lenition of voiced stops does not happen everywhere Portuguese is spoken, only some places.

Why?

More than one possible explanation comes to mind, including:

• Lenition of voiced stops was a phonologic phenomenon common to all Iberian languages which disappeared in Brazil after colonization. In other words, Brazil lost the trait.
• It was not present in the original language and developed in Portugal only after Brazil was colonized — and Brazil did not follow the same path. In other words, Portugal gained the trait.
• The Brazilian colonists came mostly from the southern part of Portugal, not the central or northern parts, and because lenition was less common in the south it never took hold in Brazil.

Certainly other possibilities also exist. Do we know what actually happened here? When did it occur? Is this a transitional process that we are now in the midst of, or is it completed?

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Examples

1. Portugal, with voiced stops lenited (“made softer”) into fricatives. Because this is fado it is sung, but the third clip has spoken examples.
2. Brazil, where they are not softened that way; they are still stops. The narrator is especially clear, although you notice it in the others as well.
3. Both, showing the contrast in this regard between the Portuguese visitor’s speech where he quite clearly softens his stops into fricatives and his Brazilian hosts, who do not do that.

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Background

This question occurred to me when I read that a speaker of Iberian Portuguese hearing a Brazilian say ou bolo might mishear it as ou polo because the European was expecting the [b] sound to become a [β] in that position, and when it didn’t, the wrong word might be momentarily (mis)understood before the context clarified it.

Answer 1

I believe the short answer is: we don't know.

Pre-tonic syllables

Scholars seem to agree that the Brazilian and European variants of Portuguese began diverging around the XVII and XVIII centuries:

PT: Os historiadores da língua portuguesa concordam em afirmar que a pronúncia do PB é mais próxima da do Português Clássico (doravante PCl) do que a do PE. Este sofreu, com efeito, possivelmente na segunda metade do séc.18 (cf: Révah, 1958; Teyssier, 1980), uma mudança fonológica que está na origem da pronúncia moderna: a chamada redução das sílabas pretônicas.

EN (unofficial translation): Historians of the Portuguese language agree in positing that the pronunciation of the Brazilian Portuguese is closer to that of Classical Portuguese than to European Portuguese. EP effectively underwent, possibly by the second half of the XVIII century, a phonological change that is the root of the modern pronunciation: the so-called reduction of the pre-tonic syllables.

Source

PT: Este [o vocalismo átono do português europeu] é um fenómeno do qual só há testemunhos directos a partir do século XVII, altura em que os textos escritos por mãos pouco alfabetizadas muito hesitam na colocação do grafema 'e' [...]

EN (unofficial translation): This [the EP's atonic vocalization] is a phenomenon of which there only are direct evidences from the XVII century onwards, at which point texts written by less-alphabetized hands hesitated greatly in placing the grapheme 'e' [...]

Source

I'll try to illustrate the reduction of the pre-tonic syllables:

• queria → BP: /kı'riɐ/ → EP: /k^ǝ'riɐ/
• possível → BP: /pʊ'sivǝw/ → EP: /p^ʊ'sivǝl/

Gerund versus "prepositioned" infinitive

Note that there is this idea of a BP being more similar to Medieval (or Classical) Portuguese. Another evidence could be the use of the gerund in BP versus "prepositioned" infinitive in EP:

• the door is closing → BP: a porta está fechando → EP: a porta está a fechar

The European Portuguese version of the sentence above would be further apart from Medieval Portuguese than the BP version. (Source)

Conclusion

I understand the reduction of pre-tonic syllables is not exactly the same phenomenon you are inquiring about, nor is the use of gerund. However, if I were to use them as proxies to the transformations both variants of Portuguese underwent, I would speculate that your second hypothesis might be true:

- It was not present in the original language and developed in Portugal only after Brazil was colonized — and Brazil did not follow the same path. In other words, Portugal gained the trait.

Answer 2

I understand that Old Spanish had two sets of voiced /b d g/ phonemes, with the non-lenited ones coming from Latin /p t k/. The ones that were often lenited, especially after vowels, were from Latin /b d g/. Since both of these sets included occlusive allophones [b d g], it was easy to confuse them, and the former eventually merged with the latter in Spanish. But in Brazilian Portuguese, the latter may have merged with the former.