シャドーイング練習: Why Do We Have More Boys Than Girls? - 動画で英語スピーキングを学ぶ

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Most parents-to-be assume that the sex of their child comes down to a flip of the chromosomal coin, with an equal chance of having a boy or a girl.

But in reality, the odds aren't even.

For every 100 girls born, the world gains about 106 baby boys.

Currently, that skewed sex ratio comes out to roughly 10 million more baby boys than girls born worldwide each year.

There are some countries where human meddling stacks the odds even higher in favor of boys, but that doesn't explain the fixed odds everywhere else.

The intrinsic boy-girl ratio is rigged by Mother Nature.

In fact, it's even more rigged than birth rates show.

Human conception results in about 150 male zygotes for every 100 females.

But there's a rather tragic reason for this big biological boy bias early on.

Male fetuses are much more likely to be miscarried or stillborn than female fetuses.

And boys that do make it out of the womb suffer more fatal diseases, take more mortal risks and fall prey to more violence than girls.

So by the time kids grow up and reach baby-making age, the ratio of males to females is just about one to one.

But the likelihood of a boy even making it to birth is also influenced by his mom's living conditions during pregnancy.

For example, when a massive famine struck China in the 1960s, the relative likelihood of having a son suddenly dropped, until the famine ended.

And male Americans born to billionaires seem to have higher than average odds of fathering sons.

Somehow, female biology suppresses boy survival in the womb during tough times and boosts it when times are good.

We've seen the same pattern in other mammals, too.

When resources are scarce, mothers give birth to fewer males than normal.

When resources are plentiful, they bear more.

The best explanation we have for this has to do with sex, the other kind.

In biological terms, the whole goal of copulation is to reproduce, to pass down your genes to someone who will someday pass them on again.

Female offspring are almost guaranteed to reproduce, famine or no famine, because male mammals are pretty much always willing to mate.

Males, on the other hand, have to compete for mating privileges.

A well-nurtured hunk has a good chance of mating with lots of females, while a male weakened by famine might not score at all.

So male offspring are a bigger risk in general.

At all stages, they're more likely to die.

And even if they live, they might not reproduce.

But when times are good, boys' potential to father lots and lots of babies make them a biological risk worth taking.

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このレッスンの語彙とスピーキングのポイント

この動画には、シャドーイング用の文が28文、単語が452語あります。音声の長さは2:27です。話す速さは速く、1分あたり約184語です。音のつながりや弱く発音される音が多くなります。英語の頻出3,000語に含まれる単語は78%だけなので、語彙は難しめです。

この動画の重要語彙

動画に出てくる覚えておきたい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
famine 名詞	/ˈfæm.ɪn/	飢饉
odd 形容詞	/ɑd/	変な, 奇異な
ratio 名詞	/ˈɹeɪ.ʃoʊ/	比
biological 形容詞	/ˌbaɪ.əˈlɑ.d͡ʒɪ.kəl/	生物学の
resource 名詞	/ɹɪˈzɔːs/	資源, 資産
likelihood 名詞	/ˈlaɪklihʊd/	可能性
offspring 名詞	/ˈɔfspɹɪŋ/	胤, 子孫
womb 名詞	/wuːm/	子宮, 母胎
fetus 名詞	/ˈfiːtəs/	胎児
relative 名詞	/ˈɹɛl.ə.tɪv/	親戚, 身内
suffer 動詞	/ˈsʌfɚ/	被る
explanation 名詞	/ˌɛkspləˈneɪʃən/	説明
guarantee 名詞	/ˌɡæɹ.ənˈtiː/	保証
compete 動詞	/kəmˈpiːt/	争う, 競う
survival 名詞	/sɚˈvaɪ.vəl/	生存, サバイバル

動画に出てくる句動詞

単語	意味
grow up 動詞	成長する, 大人に成る

注意したい発音

話し手はaren't, doesn't, they'reなど、短縮形や弱形を4回使っています。聞こえたとおりの短い形で発音しましょう。

「sh」と「zh」の音: ratio /ˈɹeɪ.ʃoʊ/, explanation /ˌɛkspləˈneɪʃən/, conception /kənˈsɛpʃən/, copulation /kɒp.jəˈleɪ.ʃən/
長い単語（アクセントの位置に注意）: biological /ˌbaɪ.əˈlɑ.d͡ʒɪ.kəl/, explanation /ˌɛkspləˈneɪʃən/, biology /baɪˈɑ.lə.d͡ʒi/, chromosomal /ˌkɹoʊməˈsoʊməl/, copulation /kɒp.jəˈleɪ.ʃən/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
まず0.75倍速で一文ずつシャドーイングし、慣れてきたら通常の速度に戻します。
自分の声を録音して元の音声と比べます。famine, odd, ratioなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: Why Do We Have More Boys Than Girls? - 動画で英語スピーキングを学ぶ

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