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As others have pointed out, it depends on how dominant or recessive the admixture is, and how distant the two populations are from each other. Sub-Saharan admixture in a European is likely to be visible from a higher single digit percentage, and vice versa, while full 50% central or northern French admixture in a Brit may not even be noticeable, as the two populations are very similar to each other, share a fairly recent common ancestor (Bell Beaker) and have been mixing for two millennia anyway.
I don't think 2% admixture is likely to be visible even in extremely distant populations. Different groups of humans are not very genetically distant to each other, even on the 'racial' level, due to our lack of long-term geographical borders meaning we frequently mix with each other throughout history. Chimpanzees, with a population of ~150,000 worldwide, are more genetically diverse than humans with our near 8 billion individuals. Our ability to build boats to cross rivers, thick coats to cross mountain ranges, and cars to make travelling extremely fast makes these geographical boundaries not really work as they do for other species. There is probably no type of admixture that would be immediately or at all visible at 2%.
I don't think you're retarded for not picking it up; I didn't even know he was half Portuguese until I saw this post. With a beard he looks mega Iberian, without he's just undiscernible European, which is fairly accurate given his ancestry.
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