I essence, if blue eyes are a recessive gene, how have they grown and subsisted over the years?
In: Biology
Because when you get three Blue-Eyes you can fuse it into Blue-Eyes Ultimate Dragon, the strongest monster in all of Duel Monsters.
A couple of factors affect this.
Firstly, selection pressure. Purely recessive genes can’t be selected *against* very easily, because 50% of all offspring will be silent carriers. Even a gene that’s fatal if expressed struggles to be selected against if its recessive, because while it kills anyone who gets gg, any child with Gg (half of all offspring) are perfectly fine and will go on to themselves have a 50% chance of passing on the recessive g to any child. Unless a recessive gene has negative effects on the carriers too, it’ll tend to remain at about the same frequency within the gene pool.
Secondly, population bottlenecks. We impose all sorts of population bottlenecks on ourselves that restrict the effective gene pool. For example, in the feudal era, it was very very unusual for peasants to move more than a few miles from their place of birth, and most remained within their birth village their entire lives. It was also very uncommon for nobles to marry peasants, whilst royalty would marry pretty much exclusively other royalty, often even going so close as their own cousins. These all bottleneck the population. If you live in a village with a 50% blue-eyed population, then even if you chose completely at random, you’d still have a 50% chance of your partner having blue eyes and thus being guaranteed to pass a blue eyes allele on. Population bottlenecks like this tend to amplify recessive genes, even ones that are typically detrimental, as seen in the Blue Fugates of America.
And once a recessive gene becomes the majority, it tends to continue to be so even as dominant alleles get introduced. Most of Europe, particularly towards the more northern parts, [have pale eyes](https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fi.imgur.com%2FriJLc2O.png&f=1&nofb=1). In the particularly blue places, the dominant dark-colour genes exist in very low frequency to begin with.
It’s also worth pointing out that eye colour doesn’t follow the normal scheme of dominant and recessive. So far, 16 different gene loci have been identified to potentially play a role in determining eye colour, so it ain’t so simple as green beats blue, brown beats green.
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