Not counting the introduction of black and Amerindian slaves, I'm thinking that in the past until after the Reconquista, these rates and degrees of exoticness and swartiness were a lot more common in south and central Spain - perhaps on much the same level as Portugal is today. But over the centuries Spain began recieving more and more European admixture, lightening them... especially in central Spain. I believe that North Africans were already present on Iberia long before the Islamic moorish conquest.
I think there's some truth in what you're saying, but I'm doubtful that Spain ever received enough people from central and northern Europe after the Reconquista to have made a big difference to the population overall. Maybe, but I think the lighter people in Spain today are more likely remnants of the Celts and Visigoths, who were pre the Islamic occupation. This is a small portion of the population though of course.
I agree about the North Africans and remember the original Iberians were very swarthy. Spain, being considerably hotter and sunnier, would probably have had a darker population than Portugal originally.
Also, lets not exaggerate the difference in light features between Spain and Portugal. While Portugal has definitely fewer fair people overall, it's not by that much. By the way one study declared Minho, the province in northern Portugal, as the area of Iberia with the highest quota of true blondes, though I don't know how reliable that is and I personally have my doubts. The key difference is rather that really exotic (mainly Sub-Saharan African-influenced) features seem to occur with notably greater frequency in the Portuguese.
Well, the Basque country (along with Wales) scores the highest in Europe for Rb1, and according to studies the scores for this in Spain (even Galicia) is overall notably higher than in Portugal - one of the highest levels in Europe - comparable to France, the UK and Ireland. The prevelence of Rb1 in Spain maybe the result of Basque along with Celtic admix. Though on a regional basis, Extremadura and western Andalucia scored quite a bit lower - very comparable to those of southern and northern Portugal. And Extremadurans have turned out to be the clostest Spaniards in the study to southern/centural Portuguese, which comes as no surprise. However, if studies were conducted to take into account the differences between the Leonese country (León, Zamora and Salamanca provinces) and those from northern Castile such as Burgos province, Segovia, etc., would probably yeald similar results. I believe that el País Llionés should be a separate region from Castilla like it originally was, anyways. Easterns Spaniards, Catalans and the Balearics, have shown to be quite distinct - which confirms the west-east distinction in Iberia that is often talked about on this forum. I imagine that southern/centural Galicians could be as close to northern Portuguese as western Extremadurans are to south/centeral Portuguese. Maybe even closer..
"Also, lets not exaggerate the difference in light features between Spain and Portugal. While Portugal has definitely fewer fair people overall, it's not by that much."
Agreed! After lots more studying of the portuguese galleries posted here and compararing them to those of the Galician, Zamoran, Salamancan and Extremaduran, I generally see very little if any difference in terms of the proportion of swarthies between them... excluding the occasional down right bizarre looking Portuguese showing more obvious amounts of SSA and other slave admix. I also so far have seen no difference at all in wogginess between southern and northern Portugal...maybe I'm wrong though? However, I've seen many more Turinid/East Asian like features amongst Extremadurans than the Portuguese. Which is curious.