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

Zašto su neki ljudi levoruki? - Danijel M. Abrams (Daniel M. Abrams)

Prevodilac: Stefan Zrnović Lektor: Mile Živković

If you know an older left-handed person,

Ako poznajete stariju levoruku osobu,

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

velike su šanse da su morali da uče ili jedu svojom desnom rukom.

And in many parts of the world,

U mnogim delovima sveta,

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

i dalje je ustaljen slučaj da teraiju decu da koriste svoju "odgovarajuću" ruku.

Even the word for right also means correct or good,

Čak i reč "right" (eng. desno) takođe znači tačno ili dobro,

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

ne samo na engleskom već i na mnogim drugim jezicima.

But if being left-handed is so wrong,

Ali ako je biti levoruk toliko pogrešno,

then why does it happen in the first place?

zašto se onda to uopšte dešava?

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

Danas je oko 1/10 svetske populacije levoruko.

Archeological evidence shows that it's been that way

Arheološki nalazi pokazuju da se ovo dešava

for as long as 500,000 years,

već 500 000 godina,

with about 10% of human remains

da oko 10% čovečanstva i dalje

showing the associated differences in arm length and bone density,

pokazuje povezane razlike u dužini ruke i gustini kostiju,

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

a neki prastari alati i artefakti dokazuju levoruko korišćenje.

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

Uprkos onome što mnogi misle, upotreba ruke nije izbor.

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

Može se predvideti čak pre rođenja na osnovu položaja fetusa u materici.

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

Ako je upotreba ruke nasledna, da li to znači da je genetski uslovljena?

Well, yes and no.

I da i ne.

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

Identični blizanci koji imaju iste gene mogu da imaju različite dominantne ruke.

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

Zapravo, ovo se javlja jednako često koliko i sa svakim drugim parom.

But the chances of being right or left-handed

Ali šanse da se postane levoruk

are determined by the handedness of your parents

su određene upotrebom ruke vaših roditelja

in surprisingly consistent ratios.

u iznenađujuće ustaljenom rasponu.

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

Ako je vaš otac bio levoruk, a vaša majka desnoruka,

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

imate 17% šansi da se rodite levoruki,

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

dok će dva dešnjaka imati levoruko dete samo u 10% slučajeva.

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

Izgleda da se upotreba ruke određuje bacanjem kockice,

but the odds are set by your genes.

ali šanse su uslovljene vašim genima.

All of this implies there's a reason

Sve ovo naznačava da postoji razlog

that evolution has produced this small proportion of lefties,

da je evolucija proizvela ovu malu proporciju levorukih,

and maintained it over the course of millennia.

i održala je tokom milenijuma.

And while there have been several theories

Iako je postojalo nekoliko teorija

attempting to explain why handedness exists in the first place,

koje su težile da objasne zašto izbor ruke uopšte postoji,

or why most people are right-handed,

ili zašto je većina ljudi desnoruko,

a recent mathematical model

skorašnji matematički model

suggests that the actual ratio reflects a balance

objašnjava da trenutna količina predstavlja balanas

between competitive and cooperative pressures on human evolution.

između takmičarskih i sarađujućih pritisaka na ljudsku evoluciju.

The benefits of being left-handed

Dobiti od levorukosti

are clearest in activities involving an opponent,

su naistaknutije u aktivnostima koje uključuju suparnika,

like combat or competitive sports.

poput borbe ili takmičarskih sportova.

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

Na primer, oko 50% najboljih udarača u bejzbolu bilo je levoruko.

Why?

Zašto?

Think of it as a surprise advantage.

Posmatrajte to kao iznenađujuću prednost.

Because lefties are a minority to begin with,

Pošto su levaci manjina,

both right-handed and left-handed competitors

levoruki i desnoruki takmičari

will spend most of their time encountering

provesšće najviše svog vremena upoznavajući

and practicing against righties.

i vežbajući protiv levaka.

So when the two face each other,

Kada se dvojica suoče,

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

levoruki će biti bolje spremljen protiv svog desnorukog takmaca,

while the righty will be thrown off.

dok će dešnjak biti izbačen.

This fighting hypothesis,

Ova borbena pretpostavka,

where an imbalance in the population

gde disbalans u stanovništvu

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

za posledicu ima prednosti za levoruke borce ili sportiste,

is an example of negative frequency-dependent selection.

primer je negativne selekcije zavisne od učestalosti.

But according to the principles of evolution,

Ali prema principima evolucije,

groups that have a relative advantage

grupe koje imaju relativne prednosti

tend to grow until that advantage disappears.

teže da rastu dok ta prednost ne nestane.

If people were only fighting and competing throughout human evolution,

Ako su se ljudi samo tukli i nadmetali kroz ljudsku evoluciju,

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

prirodna selekcija bi dovela da više levaka pobeđuje

until there were so many of them,

dok ne bude mnogo njih,

that it was no longer a rare asset.

da na kraju to ne bi ni bilo redak slučaj.

So in a purely competitive world,

U potpuno takmičarskom svetu,

50% of the population would be left-handed.

50% stanovništva bilo bi levoruko.

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

Ali ljudska evolucija je oblikovana saradnjom, ali i nadmetanjem.

And cooperative pressure

Takmičarski pritisak

pushes handedness distribution in the opposite direction.

tera podelu korišćenja ruke u suprotnom pravcu.

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

U golfu, gde nastup ne zavisi od suparnika,

only 4% of top players are left-handed,

samo je 4% najboljih igrača levoruko,

an example of the wider phenomenon of tool sharing.

kao primer šireg fenomena podele alata.

Just as young potential golfers

Kao što mladi potencijalni golferi

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

mogu lako da pronađu set štapova za desnoruke,

many of the important instruments that have shaped society

mnogi od važnih instrumenata koji su oblikovali društvo

were designed for the right-handed majority.

bili su dizajnirani za desnoruku većinu.

Because lefties are worse at using these tools,

Levaci su lošiji u korišćenju ovih alata,

and suffer from higher accident rates,

i pogađa ih veći nivo nesreća

they would be less successful in a purely cooperative world,

i bili bi manje uspešni u čisto kooperativnom svetu,

eventually disappearing from the population.

i na kraju bi nestali iz stanovništva.

So by correctly predicting the distribution

Pravilnim predviđanjem podele

of left-handed people in the general population,

levorukih ljudi u opštoj populaciji,

as well as matching data from various sports,

kao i usklađivanjem podataka iz različitih sportova,

the model indicates

model pokazuje

that the persistence of lefties as a small but stable minority

da upornost levaka, male ali stabilne manjine,

reflects an equilibrium

odaje jednakost

that comes from competitive and cooperative effects

koja potiče iz takmičarskih i sarađivačkih efekata

playing out simultaneously over time.

koji se vremenom paralelno smenjuju.

And the most intriguing thing

Najintrigantnija stvar

is what the numbers can tell us about various populations.

je šta brojevi mogu da nam kažu o različitim stanovništvima.

From the skewed distribution of pawedness in cooperative animals,

Od iskrivljene podele upotrebe šapa kod društvenih životinja,

to the slightly larger percentage of lefties

do malo manjeg procenta levaka

in competitive hunter-gatherer societies,

u takmičarskim društvima koja lovaca i sakupljača,

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

možemo čak da otkrijemo da su odgovori na neke nedoumice rane ljudske evolucije

are already in our hands.

uveliko u našim rukama.