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  • This video was sponsored by 23adnMe...and hi, I'm Emily from MinuteEarth.

    提供:23andMe こんにちは MinuteEarthのエミリーです

  • The Argentine lake duck's spiraling penis extends more than 16 inches.

    コバシオタテガモのペニスは らせん型で長さはなんと40cm

  • The seagull doesn't have a penis at all.

    一方 カモメにペニスはありません

  • For two animals with so much else in common, this is a pretty big spectrumin fact,

    こんなによく似た動物なのに ずいぶん極端な違いです

  • birds exhibit the biggest range in relative penis size of any class of vertebrates.

    鳥類のペニスの相対サイズの変異幅は 脊椎動物でもっとも大きいのです

  • And there are a couple key reasons why.


  • For one, male birds are uniquely set up to pass helpful sexual traits directly to their

    第一に 鳥のオスは繁殖に役立つ形質を 息子に直接受け継ぐことができます

  • sonstraits like showy, mate-attracting tail feathers or genitalia of certain dimensions.

    たとえば 派手で目立つ尾羽や 大げさな生殖器のことです

  • Animals generally hand these kinds of traits down through their sex chromosomesbut

    こうした形質の遺伝にはふつう 性染色体が関わりますが

  • the sex chromosomes male mammals pass on to their sons is pretty tiny and has relatively


  • few genes.


  • Male birds, on the other hand, have way bigger sex chromosomes with lots of genes, and therefore

    一方 鳥のオスの性染色体は大きく たくさん遺伝子をもっています

  • have higher chances of passing a mutationlike one for extra-sexy tail feathers

    そのため高い確率で 超セクシーな尾羽のような変異が

  • directly to their sons, who in turn can attract more mates and potentially pass a

    息子に直接受け継がれ その個体がまた多くのメスを魅了して

  • mutation for extra-extra sexy tail feathers to their sons, and so on down the line.

    超超セクシーな尾羽を孫に受け継ぎ... と続いていきます

  • In short, male birds' comparatively huge sex chromosomes are the reason much more exaggerated

    つまり オスの性染色体が 相対的に大きいことが

  • male traits have evolved in birds than in mammals.

    鳥類のオスは 哺乳類のオスより 極端な形質をもつ理由なのです

  • Like the lake duck's reeeeally long penis.

    コバシオタテガモの 超ロングなペニスもその一例

  • Male ducks often mate with unwilling females by force, and it happens that the males with

    カモのオスはしばしば 乗り気でないメスと無理やり交尾します

  • the longest and twistiest genitals are the most successful, which means the longest-and-twistiest-genital

    このとき ペニスが長くてねじれているほど 交尾の成功率が高いため

  • genes keep getting passed down from father to son.

    いちばん長くてねじれた生殖器の遺伝子が 父親から息子に受け継がれるのです

  • On the other hand, in bird species where less well-endowed males do better - maybe because

    一方 慎ましやかなオスの方が メスに好まれたり

  • females prefer them, or because big genitals make flight tough - males can end up with

    飛ぶのに邪魔にならないため 有利になった種では

  • small nubs, or even no penises at all.

    オスのペニスは小さいか まったく存在しません

  • One other reason the bird penis spectrum is so big is that it's really easy to make

    鳥類のペニスに極端な差がある もうひとつの理由は

  • a bird penis shrink.

    鳥のペニスを縮めるのが 簡単だからです

  • A single mutation on the bird's large sex chromosome triggers production of a protein


  • that basically erases the developing embyro's penis.

    発達中の胚のペニスを消し去る たんぱく質が作られます

  • All it then takes to make the entire species penis-less is for this mutation to get passed

    あとはその変異が オスからオスに伝わっていけば

  • down the line from male to male.


  • But given how the chromosomal arrangement of birds allows more male traits to change

    けれども 染色体の特徴のおかげで オスの形質が変化しやすいので

  • more easily, even penis-less-ness isn't permanent: the chachalaca, a wild cousin of

    ずっとペニスなしとも限りません 例えばキジ科のヒメシャクケイは

  • the chicken, went from having a penis, to not having one, to growing one again.

    はじめはペニスがあり いったん失われたあと もう一度ペニスを獲得したことがわかっています

  • Speaking of chromosomes, this video was sponsored by 23andMe, which has a special interest in

    染色体といえば スポンサーの23andMeは

  • the chromosomes of our own species.


  • 23andMe not only lets you learn about your own DNA story - including ancestry, personal

    ハプログループ・レポートでは 最新科学で母系と父系の先祖をたどり

  • traits and health insights - it can also help you learn which one of your parents you have


  • to thank for some of your genetic traits.


  • To get testing kits for you and your family - and to support our channel - go to

    遺伝子検査キットの請求や チャンネルの支援はこちらのアドレスまで

This video was sponsored by 23adnMe...and hi, I'm Emily from MinuteEarth.

提供:23andMe こんにちは MinuteEarthのエミリーです


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