Yes, as I suspected, the qualifications were edited out, and the editor had a clear agenda of saying 'Amazon is doing an awesome job and the fans are wrong to complain.'
So, at the end of the day, I have disagreements with the content of that interview, but that does not mean that I necessarily disagree with Corey Olsen
If only 11% of what he was saying actually made it into the video 'interview'...naturally, his emphatic statements may be missing the parts where he walked it back or qualified things.
As for the genetics of elven hair color...if that is a topic you are interested in, I suggest you check out the paper Faelivrin and I presented at Mythmoot a few years ago. It may be a bit more than anyone is looking for, but hey, if you are going to bring up a topic, and I happen to have 20 page document on that topic to hand...Imma share it
Mythmoot VI: The Genetics of Elven Hair Color
As for the topic at hand: Lúthien, Elrond, and Arwen all have the same black hair that is 'dark as shadow' that is inherited from Melian. The easiest way to achieve that outcome (especially with all of the other light-haired people in that family tree), is for Melian's dark hair to be a simple dominant trait that covers any other hair color genes present. That was why we called it 'Magic Black'. We did try to work out the inheritance patterns without that, but there is only a vanishingly small chance that Elrond and Arwen could end up with those hair colors without taking this as a very special case indeed.
We did try, very hard, to avoid that explanation of 'special Maiar genes'...but the only way to do so was to use the special case of Galadriel's hair [which we accounted for with 'roaning'] and make that a very common trait in Celeborn's family. So, it was already a special case/exception, and still only worked if you went with a 3% chance or less in multiple generations in a row to get the appropriate outcome. Possible? Yes. Likely? No. The 'Magic Black', being a simple dominant gene, had a 50% chance of being passed on to each offspring, and since we had no requirement that the trait skip a generation, nor even that all siblings in a family inherit it, it offers the simplest solution.
Incidentally, despite having two blond parents, Eärendil *could* have light brown hair (like Beren). Children having lighter (or darker) hair than their parents is possible, within a certain range. Also, while Tolkien described Eärendil as 'fair' on multiple occasions (in Fall of Gondolin), I am unaware of a passage where he explicitly stated that Eärendil is blond. Again, he can be blond. But I would not go so far as to say he *must* needs be blond.
Also, while it may seem clear to me that Elrond can only have dark hair if his mother Elwing also has dark hair, that does *not* mean that all artists have depicted Elwing with dark hair. (Tolkien never described her hair color.) Jenny Dolfen chose this shade for Elwing on account of Nimloth likely having silver hair.
The assumption that gold + silver hair can give you dark hair does not work with humans...but humans do not naturally have silver hair as a normal hair color except as an effect of aging/damage, either. Saying that silver elven hair works differently than you might expect is not an invalid interpretation of a fantasy world.
(Saying that Elrond has blond hair, when Tolkien said he didn't, is another matter entirely
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