Why are some people left-handed? - Daniel M. Abrams

Translator: Hafizh Alfarisi Reviewer: Reno Kanti Riananda

If you know an older left-handed person,

Jika kau kenal orang dewasa yang kidal,

chances are they had to learn to write or eat with their right hand.

kemungkinan mereka harus belajar menulis atau makan dengan tangan kanannya.

Di banyak tempat di dunia, sangat lazim anak disuruh memakai tangan yang “pantas”.

And in many parts of the world,

it's still common practice to force children to use their "proper" hand.

Even the word for right also means correct or good,

Bahkan kata right (kanan) juga bermakna benar atau baik.

not just in English, but many other languages, too.

Bukan hanya dalam bahasa Inggris, tetapi juga banyak bahasa lainnya.

But if being left-handed is so wrong,

Namun jika menjadi kidal itu salah, bagaimana awalnya ini terjadi?

then why does it happen in the first place?

Today, about 1/10 of the world's population are left-handed.

Saat ini, sekitar sepersepuluh populasi dunia adalah kidal.

Archeological evidence shows that it's been that way

Bukti arkeolog menyebut hal ini sudah terjadi selama 500.000 tahun.

for as long as 500,000 years,

with about 10% of human remains

Sekitar 10% sisa manusia purba menunjukkan perbedaan tersebut

showing the associated differences in arm length and bone density,

pada panjang tangan dan kepadatan tulang.

and some ancient tools and artifacts showing evidence of left-hand use.

Beberapa peralatan kuno dan artefak menunjukkan bukti penggunaan tangan kiri.

Terlepas pendapat umum, dominansi tangan bukanlah pilihan.

And despite what many may think, handedness is not a choice.

It can be predicted even before birth based on the fetus' position in the womb.

Hal ini bisa ditelaah bahkan sebelum lahir sesuai kondisi janin dalam rahim.

So, if handedness is inborn, does that mean it's genetic?

Jika dominansi tangan bawaan lahir, apa artinya ini bersifat keturunan?

Well, yes and no.

Bisa ya atau tidak.

Identical twins, who have the same genes, can have different dominant hands.

Kembar identik yang punya kesamaan gen dapat memiliki tangan dominan berbeda.

In fact, this happens as often as it does with any other sibling pair.

Bahkan ini sering terjadi dengan pasangan saudara lainnya.

But the chances of being right or left-handed

Namun, peluang menjadi kinan atau kidal ditentukan dominansi tangan orang tuamu.

are determined by the handedness of your parents

in surprisingly consistent ratios.

Rasionya ternyata selalu tetap.

If your father was left-handed but your mother was right-handed,

Bila ayahmu kidal tapi ibumu kinan, kau punya 17% peluang terlahir kidal.

you have a 17% chance of being born left-handed,

Sedangkan dua orang tua kinan hanya punya peluang 10% beranak kidal.

while two righties will have a left-handed child only 10% of the time.

Handedness seems to be determined by a roll of the dice,

Dominansi tangan kelihatannya ditentukan oleh kemungkinan,

but the odds are set by your genes.

tetapi sebenarnya didasari gen milikmu.

All of this implies there's a reason

Semua ini menyiratkan adanya alasan evolusi menghasilkan sedikit orang kidal

that evolution has produced this small proportion of lefties,

and maintained it over the course of millennia.

dan mempertahankannya selama ribuan tahun.

And while there have been several theories

Ada beberapa teori yang mencoba menjelaskan

attempting to explain why handedness exists in the first place,

kenapa dominansi tangan ada atau kenapa kebanyakan orang kinan.

or why most people are right-handed,

a recent mathematical model

Dan model matematika baru-baru ini menyimpulkan

suggests that the actual ratio reflects a balance

rasio sebenarnya mencerminkan keseimbangan

between competitive and cooperative pressures on human evolution.

antara tekanan bersaing dan bekerja sama dalam evolusi manusia.

The benefits of being left-handed

Keuntungan menjadi kidal terlihat jelas di aktivitas yang melibatkan lawan

are clearest in activities involving an opponent,

like combat or competitive sports.

seperti perkelahian atau olahraga kompetitif.

Contohnya, sekitar 50% pemukul terbaik di bisbol adalah orang kidal.

For example, about 50% of top hitters in baseball have been left-handed.

Alasannya? Anggaplah ini sebagai keunggulan kejutan.

Why?

Think of it as a surprise advantage.

Because lefties are a minority to begin with,

Karena orang kidal sedikit jumlahnya, pemain kinan dan kidal

both right-handed and left-handed competitors

will spend most of their time encountering

sering kali bertemu dan berlatih melawan orang kinan.

and practicing against righties.

So when the two face each other,

Saat keduanya bertemu, orang kidal akan lebih siap menghadapi lawan kinan

the left-hander will be better prepared against this right-handed opponent,

while the righty will be thrown off.

sementara orang kinan dibuat tak berkutik.

This fighting hypothesis,

Hipotesa pertarungan ini, yang menunjukkan ketimpangan dalam populasi

where an imbalance in the population

results in an advantage for left-handed fighters or athletes,

berujung pada keunggulan petarung atau atlet kidal,

is an example of negative frequency-dependent selection.

adalah contoh seleksi yang bergantung frekuensi negatif.

But according to the principles of evolution,

Namun, berdasarkan hukum evolusi, kelompok yang punya keunggulan relatif

groups that have a relative advantage

tend to grow until that advantage disappears.

cenderung berkembang hingga keuntungan itu hilang.

Jika orang-orang hanya bertarung dan bersaing sepanjang evolusi manusia,

If people were only fighting and competing throughout human evolution,

natural selection would lead to more lefties being the ones that made it

seleksi alam akan membuat lebih banyak orang kidal bertahan.

until there were so many of them,

Pada akhirnya, ada banyak orang kidal, sehingga itu tak lagi jadi aset langka.

that it was no longer a rare asset.

So in a purely competitive world,

Jadi, di dunia yang murni persaingan, 50% populasi akan menjadi kidal.

50% of the population would be left-handed.

But human evolution has been shaped by cooperation, as well as competition.

Namun evolusi manusia telah menciptakan kerja sama, begitu juga persaingan.

Tekanan bekerja sama mendorong penyebaran dari dominansi tangan ke arah sebaliknya.

And cooperative pressure

pushes handedness distribution in the opposite direction.

In golf, where performance doesn't depend on the opponent,

Dalam golf, ketika prestasi tak jadi tolak ukur lawan,

only 4% of top players are left-handed,

hanya 4% pemain terbaik yang kidal.

an example of the wider phenomenon of tool sharing.

Ini contoh kecil dari peristiwa peralatan massal.

Just as young potential golfers

Seperti halnya pemain golf muda berbakat yang mudah menemukan set stik golf kinan,

can more easily find a set of right-handed clubs,

many of the important instruments that have shaped society

banyak peralatan penting yang membentuk masyarakat

were designed for the right-handed majority.

dirancang untuk mayoritas orang kinan.

Because lefties are worse at using these tools,

Karena orang kidal kesusahan memakai alat-alat itu

and suffer from higher accident rates,

dan menderita dengan tingkat kecelakaan tinggi,

they would be less successful in a purely cooperative world,

mereka jadi sulit berhasil di dunia yang murni kerjasama ini.

eventually disappearing from the population.

Mereka pun akhirnya menghilang dari populasi.

Dengan mengkaji distribusi orang kidal di populasi yang luas secara tepat

So by correctly predicting the distribution

of left-handed people in the general population,

as well as matching data from various sports,

serta mencocokkan data beragam olahraga, model tersebut menunjukkan bahwa

the model indicates

that the persistence of lefties as a small but stable minority

kegigihan orang kidal sebagai minoritas yang selalu ada memunculkan kesetimbangan.

reflects an equilibrium

that comes from competitive and cooperative effects

Hal itu muncul dari dampak persaingan dan kerja sama

playing out simultaneously over time.

yang terjadi bersamaan dalam waktu lama.

And the most intriguing thing

Bagian paling menarik adalah bagaimana angka bisa menjelaskan beragam populasi.

is what the numbers can tell us about various populations.

From the skewed distribution of pawedness in cooperative animals,

Dari persebaran tak merata pada dominansi cakar hewan kooperatif

to the slightly larger percentage of lefties

hingga persentase kidal agak besar pada masyarakat pemburu peramu yang kompetitif,

in competitive hunter-gatherer societies,

we may even find that the answers to some puzzles of early human evolution

mungkin jawaban dari beberapa teka-teki di awal evolusi manusia

are already in our hands.

sudah berada di tangan kita.