Her father king Fergus is also redheaded, but her mother Elinor is not. She's brunette. How is it possible then, that all of their children are redheaded whereas the gene responsible for the red hair is a recessive polygene! The probability of them having a redheaded child is negligible if not impossible, Let alone 4 redheaded children.

What is going on?

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  • 2
    Brunettes can have the red hair gene. There's something like a 50% chance of a red headed child in that case. – Slacklord the Terrible Apr 21 '17 at 17:35
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    Well, Pixar ran the DNA tests, and it turns out they're not her children... >_> – Radhil Apr 21 '17 at 17:37
  • But the genes which are responsible for the hair color are the polygenes... meaning that different genes are required to gain a specific phenotype. – Martin Apr 21 '17 at 17:38
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    "Case 4: Parents with Brown Hair (Carrier) and Red Hair In a fourth scenario, one parent has red hair and the other has brown hair, but is a carrier of the red gene. There is a 50% chance that the children will have red hair, and a 50% chance that the children will be brown-haired carriers of the red gene." They already all have the same skin type. Compare it with the Irish. – Slacklord the Terrible Apr 21 '17 at 17:46
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    Positively Pixar's staff of genetic doctorate holders factored in all probability and assured the graphic design team of recent grad students that their casual and utterly unthought idea to make the kids just look the same was an actual real life possibility and that they should move forward with the idea. How do you ask? Same way animals talk in Disney movies. Cause it aint real, that's how. – Kai Qing Apr 21 '17 at 18:14

The odds of four independent children each being redheaded is negligible. However, the triplets are (probably) identical, right? Which means we really only have two probability events.

If the odds of any particular child being a redhead is 25%* then the probability of all four being redheads is 1/16 = 6.25%.

Which is low but hardly impossible.

Alternative answer: Disney.

*quick googling showed 25-50% as a decent odds range for children if one parent is a redhead and the other parent has ancestral redheads.

  • but this still seems pretty low, and we don't know if Elinor had redheaded ancestors, do we? – Martin Apr 21 '17 at 17:39
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    @Martin keep in mind that's the lower bound. If the odds are closer to 50% then the odds for Merida + the triplets jumps up to 25% total, which is pretty decent. And while we don't know Elinor's ancestry, if she's localish to the area then it's very possible. – Dan Smolinske Apr 21 '17 at 17:43
  • Well, if you assume identical triplets (which is very rare)... otherwise, it's the same genetic chance as any set of siblings, so indeed the odds are indeed fairly low, 1/256. – FuzzyBoots Apr 21 '17 at 18:03
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    @FuzzyBoots While identical triplets in general are pretty rare, the three in question aren't a random sample - they're pretty obviously identical. Even when you take into account that it's animation. – Dan Smolinske Apr 21 '17 at 18:10
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    @FuzzyBoots - They're stated to be identical; "Merida's identical triplet brothers are always ready to stir up a bit of mischief, especially if sweets are at stake." - movies.disney.co.uk/brave – Valorum Apr 22 '17 at 12:23

Probability doesn't work like that - for all families with one child and a set of triplets, there is a possibility that at least one family has four red-headed children. You've seen one of the families in this movie.

As FuzzyBoots says in a comment - the odds of four non-identical children being red-headed is 1/256 - not zero. Now, if the film showed 256 families all with red-headed children, we'd have to start questioning the probability.

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