Why do we have hair in such random places? - Nina G. Jablonski

Prevodilac: Jovana Babic Lektor: Milenka Okuka

We have lots in common with our closest primate relatives.

Mi imamo dosta zajedničkog sa našim bliskim rođacima primatima.

But comparatively, humans seem a bit... underdressed.

Mada u poređenju sa njima ljudi deluju... polugoli.

Instead of thick fur covering our bodies,

Umesto gustog krzna koje prekriva naše telo

many of us mainly have hair on top of our heads—

većina ljudi ima dlake na vrhu glave -

and a few other places.

i na nekoliko drugih mesta.

So, how did we get so naked? And why do we have hair where we do?

Dakle, kako smo postali toliko goli? I zašto imamo dlake na određenim mestima?

Human hair and animal fur are made of the same stuff:

Ljudska kosa i životinjsko krzno se sastoje od istog materijala:

filaments of the protein keratin that grow out of organs known as follicles,

keratinskih proteinskih filamenata koji rastu iz organa zvanih folikuli.

which go through cycles of growth and shedding.

Folikuli prolaze kroz cikluse rasta i linjanja.

Across mammalian species, hairs have been modified for numerous purposes,

Širom različitih vrsta sisara, dlaka se može naći u različitim oblicima:

ranging from the soft fluff covering rabbits

od mekog paperja kod zečeva

to the rigid quills protecting porcupines.

do krutih bodlja koje štite bodljikavo prase.

But for many mammals, hair grows in two layers

Kod mnogih sisara dlake rastu u dva sloja

consisting of a shorter undercoat of ground hairs

koji se sastoje od nižeg sloja kraćeg podkrzna

covered by longer guard hairs.

pokrivenog dužim zaštitnim dlakama.

Together, they help insulate the animal’s body and protect its skin.

Oni zajedno izoluju telo životinje i štite joj kožu.

Human hairs, on the other hand, are kind of a combination of these hair types.

Sa druge strane, ljudske dlake predstavljaju kombinaciju ova dva tipa.

Unfortunately, hair is rarely found in fossils,

Na žalost, dlake se retko mogu naći u fosilima

making it hard for researchers to pinpoint when and how

zbog čega je istraživačima teško da procene kada i kako

our ancient ancestors lost their coats.

su naši preci izgubili svoje krzno.

But scientists have developed some working hypotheses.

Uprkos tome, naučnici su konstruisali nekoliko radnih hipoteza.

It seems that, millions of years ago in Africa,

Izgleda da su pre milion godina u Africi

early hominins first transitioned out of trees and adopted a more active lifestyle.

rani hominini prvi sišli sa drveća i započeli aktivniji način života.

Keeping cool became increasingly important.

Održavanje telesne temperature je postalo prioritet.

Eventually, they developed more sweat glands,

Posledično, kod njih se povećao broj znojnih žlezda

which helped them lose heat by evaporating moisture through the skin.

koje su im omogućile gubitak toplote zbog isparavanja tečnosti sa kože.

In fact, humans have 10 times more sweat glands than chimpanzees, for instance.

Ljudi imaju 10 puta više znojnih žlezda nego šimpanze.

But efficiently losing heat by sweating is harder to do when you’re covered in fur.

Međutim, teže je postići efikasan gubitak toplote znojenjem ako je krzno prisutno

Scientists believe that early humans lost much of their coat around this time

zbog čega naučnici smatraju da su naši preci izgubili svoje krzno

to help their sweat evaporate faster.

da bi se ubrzalo isparavanje znoja.

However, if losing our hair was so advantageous,

Međutim, ako je gubitak dlaka davao toliku prednost,

why do we have any left at all?

zašto ih sada uopšte imamo?

It seems that there are unique uses for hair in different parts of our bodies.

Izgleda da postoje specifične uloge koje dlake obavljaju na raznim delovima tela.

When it comes to the tops of our heads,

Ako posmatramo vrh glave

temperature regulation likely played a part again.

onda se radi o regulaciji temperature.

Since early humans began venturing into the open,

Kada su ljudi u prošlosti počeli da izlaze na otvoreno

their heads would’ve been exposed to the scorching sun.

njihove glave su postale izložene jakim sunčevim zracima.

Thicker, longer-growing hair protects our sensitive scalps

Gusta i duga kosa štiti osetljivu poglavinu

and keeps our brains from overheating.

i sprečava pregrevanje mozga.

Dark tightly curled hair is most effective at keeping solar radiation off of skin.

Tamna kovrdžava kosa najefikasnije blokira dopiranje Sunčevih zraka do kože.

Other kinds of head hair evolved as humans moved to different places.

Ostali tipovi kose su evoluirali po selidbi ljudi u druge regione.

Meanwhile, researchers think eyebrows are especially useful for communication

Naučnici misle da su obrve veoma korisne u komunikaciji

because they sit atop active facial muscles that convey our feelings.

jer se nalaze povrh aktivnih mišića lica i tako prenose naše emocije.

Eyelashes have been shown to minimize airflow over our eyeballs,

Za trepavice je dokazano da smanjuju protok vazduha preko očnih jabučica

preventing them from drying out and catching debris.

i tako sprečavaju njihovo isušivanje i upadanja prašine.

And maybe facial hair proved helpful in distinguishing identity from a distance,

Takođe je moguće da dlake na licu pomažu u prepoznavanju ljudi sa velike udaljenosti,

but we really don’t know.

mada nismo baš sigurni za to.

Evidence is stubbly at best.

Postoji nedovoljno dokaza za ovu teoriju.

Why we have hair in other regions is... more pungent.

Razlog za prisustvo dlaka na drugim mestima je... nešto oporiji.

Our armpits, nipples, and pubic areas are dotted with apocrine glands.

Naši pazusi, bradavice i pubične zone su prožete apokrinim žlezdama.

They produce oily, smelly secretions which the thick, curly hair

One proizvode uljan sekret jakog mirisa koji raspršuju

that often grows in these spots helps disperse.

guste, kovrdžave dlake koje često rastu u ovim regionima.

The secretions that waft off these hairy patches may be useful for identification.

Miris sekreta koji se javlja u ovim zonama je možda koristan za identifikaciju.

For example, several studies have shown that people are able to identify

Na primer, više istraživanja je pokazalo da ljudi mogu da prepoznaju

their own armpit odors as well as those of people they’re close with.

miris svog pazuha, kao i mirise ljudi sa kojima su bliski.

The final type of notable human hair is the vellus hair that covers our bodies.

Poslednji tip ljudske dlake su velusne dlake koje prekrivaju celo telo.

We don't know if these hairs serve any purpose themselves,

Nismo sigurni da li ove dlake same po sebi imaju neku svrhu,

but the follicles vellus hair grows from are essential banks of stem cells

ali njihovi folikuli predstavljaju rezervoar matičnih ćelija

that repair damaged skin after injury.

koje obnavljaju oštećenu kožu.

They’re also important sites of nerve endings that convey signals

One su takođe bitne kao mesta na kojima se nalaze nervni završeci

of gentle touch to the brain.

koji prenose signale za nežan dodir do mozga

In fact, although it’s much finer,

Zapravo, iako mnogo tanje,

humans have roughly the same density of body hair as apes of comparable sizes.

ljudi imaju skoro istu gustinu telesnih dlaka kao majmuni iste veličine.

So despite all this talk of human nakedness,

Tako da uprkos celoj ovoj priči o ljudskoj golotinji,

we're not actually as hairless as we look.

mi imamo više dlaka nego što mislimo.