What Your Earwax Tells You 耳垢の話

英語の後に日本語が続きます。

Which type of earwax do you have, wet or dry? I became interested in earwax types a few days ago when I went to an ENT clinic because of a slight pain in my right ear.

I took a couple of tests at the clinic and the results showed that everything was normal, but that puzzled me. If nothing was wrong, what caused the pain? Then, it occurred to me that I hadn't cleaned my ears for years, and that might be the reason for the pain. I asked the doctor about it, and he told me something surprising. "Your ears are clean and your earwax is dry, so you don't have to clean your ears." What??? As always, I googled it and found a Japanese ENT clinic website showing the percentage of people with wet earwax below.

African	European	Micro-nesian	Taiwanese	Japanese	Mongolian	Korean	Chinese	Tungus
100％	100％	60％	40％	16％	12％	8％	4％	Very few

I also found the following information:

• The allele for wet earwax is dominant, so you only need one copy to have the trait (though two copies work as well). A recessive allele is only expressed if an individual inherits two copies without the dominant allele. (Source: BBC)
• According to Dr. Norio Niikawa, wet earwax was originally the universal human trait, but a genetic mutation arose tens of thousands of years ago in northern China and Mongolia, leading to the spread of dry earwax in those regions.

I’ve now realized how dominant and recessive alleles work, which is why I have dry earwax and my brother has wet earwax. My maternal grandma had dry earwax, too, and she was always glad to hear that I had it as well. She may have felt a special connection with me just because we shared the same type of earwax!

The pain was gone a few days later, but the term 'dry earwax' started bothering me instead. Something dry can't really be wax, can it? But then it occurred to me that English speakers mostly have wet earwax, so they don't feel anything is wrong with the term. Earwax is called 'mimi aka' in Japanese, meaning 'ear dirt.' This makes more sense to me.

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お食事中の方は食べ終わってからお読みください😁

数日前、右耳に痛みを感じ耳鼻科に行きました。検査したら何でもなかったのですが、じゃあ痛みの原因は何なんだと考えてふと思ったんです。もうずいぶん長いこと耳掃除をしていないからではないか｡｡｡ で聞いてみたら「カサカサの耳垢だから耳掃除はしなくていいです」とのこと！えっ？掃除しなくていいの？調べてみたら以下のようなことが分かりました。

湿性（ベタベタ）耳垢の割合

黒人	ヨーロッパ人	ミクロネシア人	台湾人	日本人	モンゴル人	韓国人	中国人	ツングース人
100％	100％	60％	40％	16％	12％	8％	4％	ほとんどいない

他にも｡｡｡

• ベタ耳の遺伝子が優性なので、ベタ耳遺伝子とカサ耳遺伝子の両方を持っててもベタ耳になる。
• 北海道医療大学の新川詔夫学長によると、もともと人間の耳垢はすべて湿型だったが、数万年前の中国北部やモンゴルの周辺での遺伝子の突然変異で、乾型の耳垢が生まれ、周辺地域に広がった。

両親も弟もベタ耳なのに、私だけカサ耳ということは、両親はベタ耳遺伝子（優性）とカサ耳遺伝子（劣性）の両方を持っているせいだということが分かりました。かつ、カサ耳の祖母が私がカサ耳なのを知るとえらく喜んでいたことも思い出しました。（カサ耳親近感ね。）

数日後、痛みは消えたのですが、以来、別のことが気になっています。英語で耳垢って「earwax」というのですが、カサカサの耳あかを earwax っておかしくありませんか？Waxって蝋（ロウ）でしょ。カサカサじゃないでしょ｡｡｡ そっか。英語圏はほぼベタ耳なのね。

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