So how did so many Berbers end up in Portugal? One keeps hearing about this supposed huge sub-saharan admixture in Portugal (that in fact is quite small)--but was this Berber thing a slave trade or just migration--either way, we don't read about it in the history books.

"Negroid" would be a phenotype, not a geneotype. You underlying theory is flawed.

"either way, we don't read about it in the history books."

If this percentages are real it doesnt say something really new to people already familiar this matters at all.

It doesnt mean Subsaharan African admixture because the most pure Berbers are Europids/Caucasoids and are of Mediterranid and Upper Palaeolithic/Alpinoid variants.

“the most pure Berbers are Europids/Caucasoids and are of Mediterranid and Upper Palaeolithic/Alpinoid variants.”

I would like to know who are the purest “Berbers” since “Berber” refers more appropiately to a language and culture, not a phenotype. Berbers have a wide range of phenotypes so which one is the “purest” one?

I am actually half berber, so I think I can shed some light on the issue. The people today associated as being berber are the descendents of such ancient peoples as the Carthaginian's, the Numidians, and the Almorhavids. By the way to answer your question about why the gene is prevalent most on the Iberian peninsula is due to the fact that the Almorhavid empire controlled areas in southern Iberia for a great deal of time and would likely of mixed into some of the pop. Currently the majority of people in North Africa are berber or are weighted more towards being berber than anything else. A absolutely pure berber would be more easily found in the sahara because the Arab conquest did not wish to engage in a worthless campaign through an expansive desert. Facial lines and distinctions associated with a berber would include: Thick protruding eyebrow bone, Thick long eyebrows, very spanish looking nose, eyes not too dissimilar to a portuguese person, but even hawkier and bigger if that makes any sense, A fat lower lip like a greek, and round chin and cheeks, lasly a year round tan. As for the body very hairy, on average a very wide frame, with usually short hamstrings and naturally muscular legs built to trudging through sandy desert, poor posture very common, dont like to make fun of myself but our body frame is almost apeish, and a italian like year round tan. When not with a desert tan a berber can often be mistaken for being Iberian or Greek. Also an example of their relation to europeans, there are some that instead of having blackish hair brown eyes, they have blonde hair and blue eyes.
Berber's are a people just as slavic's or germanics are a people within the europid group. Most berber's who are part Arab would rather just call themselves arab(demonstarted by the 50% having Haplogroup E-M81 in the non berber pop. of North Africa).
So the people who remain calling themselves berber are mostly of true North African ancestrial descent demonstarted by the 80% who have Haplogroup E-M81.
Berber's ARE A people with an associated phenotype not just a language and culture. That would be like saying Germanics don't have a phenotype and are just a few languages and cultures, and not a people because they contain some Slavic, and Western european phenotypes.

Berber's do not contain a large array of Phenotypes, but one main Phenotype, the ancestral North African Phenotype. To dispel Charlie Bass's accusation, a person who probably knows very little of the Berber people, so therefore does not have the knowledge to make statements on the subject.