TEDGlobal 2013
Suzana Herculano-Houzel: What is so special about the human brain?
Suzana Herculano-Houzel: Što je tako posebno oko ljudskog mozga?
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Ljudski mozak je zagonetan – zanimljivo je velik naspram naših tijela, koristi ogromnu količinu energije za svoju težinu i ima bizarno gustu moždanu koru. Ali zašto? Neuroznanstvenik Suzana Herculano-Houzel stavlja svoju detektivsku kapu i vodi nas kroz ovu misteriju. Praveći “juhu od mozga” dolazi do zastrašujućeg zaključka.
Suzana Herculano-Houzel - Neuroscientist
Suzana Herculano-Houzel shrunk the human brain by 14 billion neurons -- by developing a new way to count them. Full bio
Suzana Herculano-Houzel shrunk the human brain by 14 billion neurons -- by developing a new way to count them. Full bio
Double-click the English transcript below to play the video.
00:12
What is so special about the human brain?
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Što je tako posebno oko ljudskog mozga?
00:15
Why is it that we study other animals
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Zašto smo mi ti koji proučavamo druge životinje,
00:17
instead of them studying us?
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a ne one nas?
00:19
What does a human brain have or do
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Što to ljudski mozak ima ili radi
00:21
that no other brain does?
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što nijedan drugi mozak ne radi?
00:23
When I became interested
in these questions about 10 years ago,
in these questions about 10 years ago,
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Kada sam se počela zanimati za ova pitanja prije 10 godina,
00:26
scientists thought they knew
what different brains were made of.
what different brains were made of.
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znanstvenici su mislili da znaju od čega su sačinjeni različiti mozgovi.
00:28
Though it was based on very little evidence,
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Iako je postojalo vrlo malo dokaza,
00:30
many scientists thought that all mammalian brains,
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mnogi znanstvenici su mislili da je mozak sisavaca,
00:32
including the human brain,
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uključujući i ljudski mozak,
00:34
were made in the same way,
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sačinjen na isti način,
00:35
with a number of neurons that was always
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s brojem neurona koji su uvijek
00:37
proportional to the size of the brain.
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proporcionalni veličini mozga.
00:39
This means that two brains of the same size,
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To znači da dva mozga jednake veličine,
00:41
like these two, with a respectable 400 grams,
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poput ova dva, s dobranih 400 grama,
00:45
should have similar numbers of neurons.
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bi trebali imati sličan broj neurona.
00:47
Now, if neurons are the functional
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Sad, ako su neuroni funkcionalna
00:49
information processing units of the brain,
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jedinica mozga koja procesuira informacije,
00:52
then the owners of these two brains
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tada bi vlasnici ovih mozgova
00:54
should have similar cognitive abilities.
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trebali imati slične kognitivne sposobnosti.
00:56
And yet, one is a chimp,
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A ipak, jedna je čimpanza,
00:59
and the other is a cow.
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a druga je krava.
01:01
Now maybe cows have a really rich
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Sad, moguće je da krave imaju vrlo bogat
01:04
internal mental life and are so smart
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unutarnji mentalni život i da su toliko pametne
01:06
that they choose not to let us realize it,
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da nam ne dopuštaju da to vidimo,
01:10
but we eat them.
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ali mi ih jedemo.
01:11
I think most people will agree
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Mislim da će se većina ljudi složiti
01:13
that chimps are capable of much more complex,
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da su čimpanze sposobne za mnogo složenije,
01:15
elaborate and flexible behaviors than cows are.
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planirano i fleksibilno ponašanje nego krave.
01:18
So this is a first indication that the
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To je prvi pokazatelj da
01:20
"all brains are made the same way" scenario
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„svi su mozgovi sačinjeni na isti način“ scenarij
01:22
is not quite right.
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nije sasvim točan.
01:24
But let's play along.
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Ali hajdemo se zabaviti.
01:25
If all brains were made the same way
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Ako su svi mozgovi sačinjeni na isti način
01:27
and you were to compare animals
with brains of different sizes,
with brains of different sizes,
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i ako ćemo uspoređivati životinje
s mozgovima različitih veličina,
s mozgovima različitih veličina,
01:30
larger brains should always have more neurons
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veći mozgovi bi uvijek trebali imati više neurona
01:32
than smaller brains,
and the larger the brain,
and the larger the brain,
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no mali mozgovi, i što je veći mozak,
01:34
the more cognitively able its owner should be.
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veće su kognitivne sposobnosti njegovog vlasnika.
01:37
So the largest brain around should also be
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Znači najveći mozak koji postoji bi trebao
01:39
the most cognitively able.
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biti kognitivno najsposobniji.
01:42
And here comes the bad news:
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I ovdje dolaze loše vijesti:
01:43
Our brain, not the largest one around.
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Naš mozak nije najveći.
01:46
It seems quite vexing.
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To je poprilično zbunjujuće.
01:47
Our brain weighs between 1.2 and 1.5 kilos,
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Naš mozak teži između 1.2 i 1.5 kila,
01:50
but elephant brains weigh between four and five kilos,
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ali mozak slona teži između četiri i pet kila,
01:54
and whale brains can weigh up to nine kilos,
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a mozak kitova može težiti i devet kila
01:56
which is why scientists used to resort to saying
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zbog čega znanstvenici sa sigurnošću tvrde
02:01
that our brain must be special
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da je naš mozak poseban
02:03
to explain our cognitive abilities.
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kako bi objasnili naše kognitivne sposobnosti.
02:06
It must be really extraordinary,
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Stvarno mora biti izvanredan,
02:09
an exception to the rule.
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iznimka pravilu.
02:11
Theirs may be bigger, but ours is better,
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Možda je njihov veći, ali naš je bolji,
02:14
and it could be better, for example,
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i mogao bi biti bolji, na primijer,
02:16
in that it seems larger than it should be,
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u tome što se čini većim no što je,
02:18
with a much larger cerebral cortex
than we should have
than we should have
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s mnogo većom moždanom korom no što bi trebali imati
02:21
for the size of our bodies.
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Za veličinu našeg tijela.
02:22
So that would give us extra cortex
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To bi nam dalo dodatne kore
02:24
to do more interesting things
than just operating the body.
than just operating the body.
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kako bi smo radili zanimljivije stvari
nego samo upravljali tijelom.
nego samo upravljali tijelom.
02:27
That's because the size of the brain
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To je zato jer veličina mozga
02:29
usually follows the size of the body.
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obično prati veličinu tijela.
02:31
So the main reason for saying that
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Zato je glavni razlog za tvrdnju da
02:33
our brain is larger than it should be
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je naš mozak veći no što bi trebao biti
02:35
actually comes from comparing ourselves
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zapravo dolazi od usporedbe nas
02:37
to great apes.
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s velikim primatima.
02:39
Gorillas can be two to three times larger than we are,
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Gorile mogu biti dva do tri puta veće od nas,
02:41
so their brains should also be larger than ours,
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pa bi i njihovi mozgovi također trebali biti veći od naših,
02:44
but instead it's the other way around.
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ali zapravo je obrnuto.
02:46
Our brain is three times larger than a gorilla brain.
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Naš mozak je tri puta veći od mozga gorile.
02:49
The human brain also seems special
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Ljudski mozak je također poseban
02:51
in the amount of energy that it uses.
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po količini energije koju koristi.
02:53
Although it weighs only two percent of the body,
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Iako teži samo 2% našeg tijela,
02:56
it alone uses 25 percent of all the energy
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sam koristi 25% cjeloukupne energije
02:59
that your body requires to run per day.
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koje naše tijelo treba u jednom danu.
03:02
That's 500 calories out of a total of 2,000 calories,
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To je otprilike 500 kalorija od sveukupnih 2000 kalorija,
03:05
just to keep your brain working.
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samo kako bi vam mozak radio.
03:07
So the human brain is larger than it should be,
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Znači ljudski mozak je veći no što bi trebao biti,
03:10
it uses much more energy than it should,
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koristi puno više energije no što bi trebao,
03:12
so it's special.
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pa je poseban.
03:14
And this is where the story started to bother me.
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I ovdje me je priča počela mučiti.
03:16
In biology, we look for rules
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U biologiji tražimo zakone
03:18
that apply to all animals and to life in general,
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koji su primjenjivi na sve životinje i život generalno,
03:21
so why should the rules of evolution
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pa zašto bi zakoni evolucije
03:23
apply to everybody else but not to us?
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bili primjenjivi na sve osim nas?
03:26
Maybe the problem was with the basic assumption
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Možda je problem sa osnovnom pretpostavkom
03:29
that all brains are made in the same way.
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da su svi mozgovi sačinjeni jednako.
03:30
Maybe two brains of a similar size
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Možda dva mozga slične veličine
03:32
can actually be made of
very different numbers of neurons.
very different numbers of neurons.
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mogu zapravo biti sačinjeni od različitog broja neurona.
03:35
Maybe a very large brain
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Možda veoma velik mozak
03:36
does not necessarily have more neurons
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ne mora nužno imati više neurona
03:38
than a more modest-sized brain.
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od nekog mozga umjerene veličine.
03:40
Maybe the human brain
actually has the most neurons
actually has the most neurons
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Možda ljudski mozak zapravo ima najvišen neurona
03:43
of any brain, regardless of its size,
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nego bilo koji mozak, neovisno o njegovoj veličini,
03:46
especially in the cerebral cortex.
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posebno u moždanoj kori.
03:48
So this to me became
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To mi je postalo
03:50
the important question to answer:
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važno pitanje za odgovoriti:
03:51
how many neurons does the human brain have,
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koliko neurona ima ljudski mozak,
03:54
and how does that compare to other animals?
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i kako to izgleda u usporedbi s drugim životinjama?
03:56
Now, you may have heard or read somewhere
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Sad, možda ste čuli ili pročitali negdje
03:59
that we have 100 billion neurons,
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da imamo 100 milijardi neurona,
04:01
so 10 years ago, I asked my colleagues
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i prije 10 godina, pitala sam svoje kolege
04:03
if they knew where this number came from.
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znaju li odakle je došao taj broj.
04:05
But nobody did.
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Nitko nije znao.
04:06
I've been digging through the literature
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Kopala sam po literaturi
04:08
for the original reference for that number,
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kako bi pronašla originalnu referencu na taj broj,
04:10
and I could never find it.
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i nisam ju mogla pronaći.
04:11
It seems that nobody had actually ever counted
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Izgleda da nitko nije zapravo prebrojao
04:14
the number of neurons in the human brain,
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broj neurona u ljudskom mozgu,
04:16
or in any other brain for that matter.
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ili u bilo kojem drugom mozgu zapravo.
04:18
So I came up with my own way
to count cells in the brain,
to count cells in the brain,
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Pa sam pronašla svoj način kako prebrojati stanice u mozgu,
04:22
and it essentially consists of
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a zapravo se sastoji od
04:24
dissolving that brain into soup.
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otapanja mozga u juhu.
04:27
It works like this:
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Ovako nekako ide:
04:29
You take a brain, or parts of that brain,
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Uzmete mozak, ili dijelove mozga,
04:32
and you dissolve it in detergent,
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i otopite ih u deterdžentu,
04:34
which destroys the cell membranes
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što uništi membrane stanica
04:35
but keeps the cell nuclei intact,
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ali ostavi stanične jezgre netaknutima,
04:38
so you end up with a suspension of free nuclei
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pa dobijete otopinu slobodnih jezgara
04:41
that looks like this,
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koje izgledaju ovako,
04:43
like a clear soup.
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poput čiste juhe.
04:44
This soup contains all the nuclei
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Ova juha sadrži sve jezgre
04:46
that once were a mouse brain.
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koje su bile mišji mozak.
04:48
Now, the beauty of a soup is that because it is soup,
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Sad, ljepota ove juhe je to što je to juha,
04:51
you can agitate it and make those nuclei
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možete ju izmućkati i sve te jezgre
04:54
be distributed homogeneously in the liquid,
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homogeno raspršiti u tekućini,
04:56
so that now by looking under the microscope
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tako da ako gledamo ispod mikroskopa
04:58
at just four or five samples
of this homogeneous solution,
of this homogeneous solution,
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samo četiri ili pet uzoraka
05:02
you can count nuclei, and therefore tell
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možete prebrojati jezgre, a time i saznati
05:05
how many cells that brain had.
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koliko mnogo stanica postoji u mozgu.
05:06
It's simple, it's straightforward,
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Jednostavno je, direktno,
05:08
and it's really fast.
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i stvarno brzo.
05:09
So we've used that method to count neurons
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Koristili smo ovu metodu kako bi izbrojali neurone
05:11
in dozens of different species so far,
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u nekoliko različitih vrsta zasad,
05:14
and it turns out that all brains
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i pokazalo se da svi mozgovi
05:15
are not made the same way.
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nisu sačinjeni jednako.
05:18
Take rodents and primates, for instance:
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Uzmite glodavce i primate, na primjer:
05:20
In larger rodent brains, the average size
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U najvećem mozgu glodavca, prosječan broj
05:22
of the neuron increases,
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neurona raste,
05:24
so the brain inflates very rapidly
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tako da mozak širi jako brzo
05:27
and gains size much faster than it gains neurons.
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i raste puno brže no što dobija neurone.
05:30
But primate brains gain neurons
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Ali mozgovi primata dobijaju neurone
05:32
without the average neuron becoming any larger,
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bez da prosječan neuron postaje veći,
05:34
which is a very economical way
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što je jako ekonomičan način
05:35
to add neurons to your brain.
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dodavanja neurona u mozak.
05:37
The result is that a primate brain
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Rezultat je to da će mozak primata
05:39
will always have more neurons than
a rodent brain of the same size,
a rodent brain of the same size,
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uvijek imati više neurona nego mozak glodavca iste veličine,
05:42
and the larger the brain,
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i što je veći mozak,
05:44
the larger this difference will be.
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veća će razlika biti.
05:46
Well, what about our brain then?
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A što je s našim mozgovima?
05:48
We found that we have, on average,
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Saznali smo da imamo, prosječno,
05:50
86 billion neurons,
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oko 89 milijardi neurona,
05:51
16 billion of which are in the cerebral cortex,
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od toga 16 milijardi su u moždanoj kori,
05:54
and if you consider that the cerebral cortex
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i ako uzmete u obzir to da je moždana kora
05:56
is the seat of functions like
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sjedište funkcija poput
06:00
awareness and logical and abstract reasoning,
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pažnje, logičnog i apstraktnog razmišljanja,
06:03
and that 16 billion is the most neurons
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i da je 16 milijardi najviše neurona
06:06
that any cortex has,
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što ikoja moždana kora ima,
06:08
I think this is the simplest explanation
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mislim da je to najjednostavnije objašnjenje
06:10
for our remarkable cognitive abilities.
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naših izvanrednih kognitivnih sposobnosti.
06:13
But just as important is what
the 86 billion neurons mean.
the 86 billion neurons mean.
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Ali jednako važno je i to što 86 milijardni neurona znači.
06:16
Because we found that the relationship
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Jer saznali smo da se veza
06:18
between the size of the brain
and its number of neurons
and its number of neurons
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između veličine mozga i broja njegovih neurona
06:20
could be described mathematically,
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može matematički objasniti,
06:22
we could calculate what a human brain
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možemo izračunati kako bi
06:24
would look like if it was made like a rodent brain.
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ljudski mozak izgledao da je sačinjen kao mozak glodavaca.
06:27
So, a rodent brain with 86 billion neurons
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Mozak glodavca sa 86 milijardi neurona
06:30
would weigh 36 kilos.
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težio bi 36 kila.
06:33
That's not possible.
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To nije moguće.
06:35
A brain that huge would be crushed
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Tako veliki mozak bi se urušio
06:37
by its own weight,
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zbog svoje težine,
06:38
and this impossible brain would go
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i ovakav nemoguć mozak bi morao
06:40
in the body of 89 tons.
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biti u tijelu od 89 tona.
06:44
I don't think it looks like us.
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Mislim da to ne izgleda kao mi.
06:46
So this brings us to a very important
conclusion already,
conclusion already,
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Ovo nas već dovodi do jako važnog zaključka,
06:48
which is that we are not rodents.
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a to je da nismo glodavci.
06:51
The human brain is not a large rat brain.
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Ljudski mozak nije veliki mozak štakora.
06:54
Compared to a rat, we might seem special, yes,
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U usporedbi sa štakorom, možda se činimo posebnima, da
06:57
but that's not a fair comparison to make,
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ali to nije pošteno napravljena usporedba
06:59
given that we know that we are not rodents.
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jer mi znamo da nismo glodavci.
07:01
We are primates,
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Mi smo primati,
07:02
so the correct comparison is to other primates.
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pa je pošteno da se uspoređujemo sa ostalim primatima
07:05
And there, if you do the math,
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i ako izračunate,
07:06
you find that a generic primate
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vidjeli bi da svaki primat
07:09
with 86 billion neurons
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1930
sa 86 milijardi neurona
07:11
would have a brain of about 1.2 kilos,
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3003
bi imao mozak težine otprilike 1.2 kile,
07:14
which seems just right,
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1889
što nam odgovara,
07:16
in a body of some 66 kilos,
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1972
u tijelu od nekih 66 kila,
07:18
which in my case is exactly right,
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što je u mom slučaju istina,
07:21
which brings us to a very unsurprising
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što nas dovodi do neiznenađujućeg
07:23
but still incredibly important conclusion:
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ali ipak vrlo važnog zaključka:
07:26
I am a primate.
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Ja sam primat.
07:28
And all of you are primates.
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Svi ste vi primati.
07:30
And so was Darwin.
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1900
I Darwin je bio.
07:32
I love to think that Darwin
would have really appreciated this.
would have really appreciated this.
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Volim misliti da bi Darwin
ovo stvarno cijenio.
ovo stvarno cijenio.
07:35
His brain, like ours,
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1967
Njegov mozak, poput naših,
07:37
was made in the image of other primate brains.
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3511
je sačinjen po istoj slici kao i mozak drugih primata.
07:41
So the human brain may be remarkable, yes,
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2302
Ljudski mozak je nevjerovatan, da,
07:43
but it is not special in its number of neurons.
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ali nije poseban po svome broju neurona.
07:46
It is just a large primate brain.
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1855
To je samo veliki mozak primata.
07:48
I think that's a very humbling and sobering thought
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Mislim da je to veoma skromno i razborito mišljenje
07:51
that should remind us of our place in nature.
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koje bi nas trebalo podsjetiti na naše mjesto u prirodi.
07:54
Why does it cost so much energy, then?
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Zašto onda koristi toliko energije?
07:56
Well, other people have figured out
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Drugi ljudi su zapravo otkrili
07:58
how much energy the human brain
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1503
koliko energije ljudski mozak
07:59
and that of other species costs,
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1407
i mozak drugih vrsta troši,
08:01
and now that we knew how many neurons
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i sada kada smo znali koliko neurona
08:02
each brain was made of, we could do the math.
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svaki mozak ima, mogli smo to izračunati.
08:05
And it turns out that both human
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I ispalo je da ljudski mozak
08:07
and other brains cost about the same,
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2823
i drugi mozgovi troše otprilike jednako,
08:09
an average of six calories
per billion neurons per day.
per billion neurons per day.
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prosječno šest kalorija po milijardi neurona na dan.
08:13
So the total energetic cost of a brain
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Konačni utrošak energije mozga je
08:15
is a simple, linear function
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2034
jednostavno, linearna funkcija
08:17
of its number of neurons,
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1709
njegovog broja neurona,
08:19
and it turns out that the human brain
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2183
i ispalo je da ljudski mozak
08:21
costs just as much energy as you would expect.
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3841
troši onoliko energije koliko bi ste očekivali.
08:25
So the reason why the human brain
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2091
Razlog zašto ljudski mozak
08:27
costs so much energy is simply because
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495271
1672
troši toliko energije je jednostavno jer
08:28
it has a huge number of neurons,
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496943
1983
ima velik broj neurona,
08:30
and because we are primates
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1485
i zato što smo primati
08:32
with many more neurons for a given body size
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s mnogo više neurona za našu tjelesnu veličinu
08:34
than any other animal,
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1522
nego druge životinje,
08:36
the relative cost of our brain is large,
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3540
relativni utrošak našeg mozga je velik,
08:39
but just because we're primates,
not because we're special.
not because we're special.
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507972
3001
samo zato što smo primati,
ne zato što smo posebni.
ne zato što smo posebni.
08:42
Last question, then:
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1190
Posljednje pitanje, onda:
08:44
how did we come by this
remarkable number of neurons,
remarkable number of neurons,
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512163
3115
kako smo dobili
poveći broj neurona,
poveći broj neurona,
08:47
and in particular, if great apes
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515278
1900
i specifično, ako su veliki primati
08:49
are larger than we are,
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1555
veći od nas,
08:50
why don't they have a larger brain
than we do, with more neurons?
than we do, with more neurons?
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3765
zašto nemaju veće mozgove
od nas, s više neurona?
od nas, s više neurona?
08:54
When we realized how much expensive it is
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2090
Kada smo shvatili koliko bi skupo bilo
08:56
to have a lot of neurons in the brain, I figured,
228
524588
2333
imati toliko neurona u mozgu, shvatila sam,
08:58
maybe there's a simple reason.
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526921
2003
možda postoji jednostavno rješenje.
09:00
They just can't afford the energy
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528924
1683
Jednostavno ne mogu priuštiti toliko energije
09:02
for both a large body
and a large number of neurons.
and a large number of neurons.
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2950
i za veliko tijelo i za velik broj neurona.
09:05
So we did the math.
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Bavili smo se matematikom.
09:06
We calculated on the one hand
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1600
Izračunali smo u jednu ruku
09:08
how much energy a primate gets per day
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536586
1941
koliko energije primat dobije na dan
09:10
from eating raw foods,
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1350
jedeći sirovu hranu,
09:11
and on the other hand, how much energy
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2037
i u drugu ruku, koliko energije
09:13
a body of a certain size costs
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541914
1764
troši tijelo određene veličine,
09:15
and how much energy a brain of a
certain number of neurons costs,
certain number of neurons costs,
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3387
i koliko energije troši mozak s određenim brojem neurona,
09:19
and we looked for the combinations
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1489
i pogledali smo kombinacije
09:20
of body size and number of brain neurons
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veličine tijela i broja neurona
09:22
that a primate could afford
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1270
koje primat može priuštiti
09:24
if it ate a certain number of hours per day.
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ako jede određen broj sati po danu.
09:26
And what we found is that
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1816
I otkrili smo da
09:28
because neurons are so expensive,
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1712
pošto su neuroni tako skupi,
09:30
there is a tradeoff between
body size and number of neurons.
body size and number of neurons.
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558311
3370
postoji kompromis između
tjelesne veličine i broja neurona.
tjelesne veličine i broja neurona.
09:33
So a primate that eats eight hours per day
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2951
Primati koji jedu osam sati na dan
09:36
can afford at most 53 billion neurons,
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3024
mogu priuštiti najviše 53 milijardi neurona,
09:39
but then its body cannot be any bigger
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1727
ali onda njihovo tijelo ne može biti veće
09:41
than 25 kilos.
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569383
1954
Od 25 kila.
09:43
To weigh any more than that,
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1701
Kako bi težilo više,
09:45
it has to give up neurons.
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1769
mora se odreći neurona.
09:46
So it's either a large body
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2653
Može biti ili veliko tijelo
09:49
or a large number of neurons.
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1495
ili veliki broj neurona.
09:50
When you eat like a primate,
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1365
Kada jedete kao primat,
09:52
you can't afford both.
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580320
2236
ne možete priuštiti oboje.
09:54
One way out of this metabolic limitation
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582556
1964
Jedini način kako izaći iz ovog metaboličkog ograničenja
09:56
would be to spend even more hours per day eating,
257
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3401
je provesti još više sati na dan jedući,
09:59
but that gets dangerous,
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1363
ali ovdje priča postaje nategnuta,
10:01
and past a certain point, it's just not possible.
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589284
2719
u jednom trenutku to više neće biti moguće.
10:04
Gorillas and orangutans, for instance,
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592003
1537
Gorile i orangutani, na primijer,
10:05
afford about 30 billion neurons
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593540
1923
su si priuštili 30 milijardi neurona
10:07
by spending eight and a half hours per day eating,
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2966
jedući osam i pol sati na dan,
10:10
and that seems to be about as much as they can do.
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3116
I to je otprilike najviše što mogu.
10:13
Nine hours of feeding per day
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1791
Devet sati hranjenja na dan
10:15
seems to be the practical limit for a primate.
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3271
izgleda da je stvarni limit za primate.
10:18
What about us?
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1791
Što je s nama?
10:20
With our 86 billion neurons
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1600
S naših 86 milijardi neurona
10:21
and 60 to 70 kilos of body mass,
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3035
i 60 do 70 kila tjelesne mase,
10:25
we should have to spend over nine hours
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3561
trebali bi provesti više od devet sati
10:28
per day every single day feeding,
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3575
po danu svaki put kada se hranimo,
10:32
which is just not feasible.
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2039
što jednostavno nije izvodljivo.
10:34
If we ate like a primate,
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622208
1834
Ako jedemo poput primata,
10:36
we should not be here.
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2253
ne bi smo trebali biti ovdje.
10:38
How did we get here, then?
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2127
Kako smo dospjeli onda ovdje?
10:40
Well, if our brain costs just as much energy
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2735
Pa, ako naš mozak troši onoliko energije
10:43
as it should, and if we can't spend
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631157
1723
koliko bi trebalo, i ako možemo potrošiti
10:44
every waking hour of the day feeding,
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3674
svaki budni sat u danu hraneći se,
10:48
then the only alternative, really,
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636554
1911
onda je jedino rješenje, zapravo,
10:50
is to somehow get more energy
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638465
1958
da nekako dobijemo više energije
10:52
out of the same foods.
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640423
1953
iz iste hrane.
10:54
And remarkably, that matches exactly
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3800
I značajno, to odgovara upravo
10:58
what our ancestors are believed to have invented
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3037
onome što se vjeruje da su naši preci izumili
11:01
one and a half million years ago,
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1839
prije jedan i pol milijun godina,
11:03
when they invented cooking.
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2782
a to je kuhanje.
11:05
To cook is to use fire
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653834
1970
Kuhanje je korištenje vatre
11:07
to pre-digest foods outside of your body.
286
655804
3800
kako bi se predprobavila hrana izvan našeg tijela.
11:11
Cooked foods are softer, so they're easier to chew
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2606
Kuhana hrana je mekša, lakša je za žvakanje
11:14
and to turn completely into mush in your mouth,
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2563
i pretvarajući se potpuno u kašu u našim ustima,
11:16
so that allows them to be completely digested
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2152
dozvoljava joj se da bude potpuno probavljena
11:18
and absorbed in your gut,
290
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1436
i apsorbirana u našoj probavi,
11:20
which makes them yield much more
energy in much less time.
energy in much less time.
291
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3655
što omogućava puno više energije u manje vremena.
11:24
So cooking frees time for us to do
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2489
Kuhanje nam oslobađa vrijeme kako bi radili
11:26
much more interesting things with our day
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2062
puno zanimljivije stvari s našim vremenom
11:28
and with our neurons
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1480
i s našim neuronima
11:30
than just thinking about food,
295
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1905
nego samo razmišljati o hrani,
11:31
looking for food, and gobbling down food
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1704
tražiti hranu i trpati ju u nas
11:33
all day long.
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1225
cijeli dan.
11:34
So because of cooking, what once was
298
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2499
Znači zbog kuhanja, što je prije bila
11:37
a major liability, this large,
299
685380
2353
velika prepreka, ovaj veliki,
11:39
dangerously expensive brain with a lot of neurons,
300
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3033
opasno skup mozak s puno neurona,
11:42
could now become a major asset,
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690766
2036
je uspio postati od velike važnosti,
11:44
now that we could both afford
the energy for a lot of neurons
the energy for a lot of neurons
302
692802
3251
sad kad možemo priuštiti i
energiju za mnogo neurona
energiju za mnogo neurona
11:48
and the time to do interesting things with them.
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2503
i vrijeme da radimo zanimljive stvari s njima.
11:50
So I think this explains why the human brain
304
698559
1974
Mislim da ovo objašnjava zašto je ljudski mozak
11:52
grew to become so large so fast in evolution,
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3240
postao tako velik tako brzo u evoluciji,
11:55
all of the while remaining just a primate brain.
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3897
ali i ostao samo mozak primata.
11:59
With this large brain now affordable by cooking,
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2774
S ovim velikim mozgom koji je omogućilo kuhanje,
12:02
we went rapidly from raw foods to culture,
308
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2913
ubrzo smo prešli sa sirove hrane do kulture,
12:05
agriculture, civilization, grocery stores,
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2606
poljoprivrede, civilizacije, trgovina s hranom,
12:07
electricity, refrigerators,
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1625
struje, hladnjaka,
12:09
all of those things that nowadays
311
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1607
svih tih stvari koje nam danas
12:11
allow us to get all the energy we need
312
719195
2042
dopuštaju da dobijemo svu energiju koju trebamo
12:13
for the whole day in a single sitting
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2782
kako bi smo cijeli dan proveli samo sjedeći
12:16
at your favorite fast food joint.
314
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2954
u vašem najdražem fast food restoranu.
12:18
So what once was a solution
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2437
Ono što je jednom bilo riješenje
12:21
now became the problem,
316
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1699
sada je postalo problem,
12:23
and ironically, we look for the solution in raw food.
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5517
i ironično, tražimo rješenje u sirovoj hrani.
12:28
So what is the human advantage?
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2556
Što je ljudska prednost?
12:31
What is it that we have
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1503
Što je to što imamo
12:32
that no other animal has?
320
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2535
a što druge životinje nemaju?
12:35
My answer is that we have the largest number
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2348
Moj odgovor je da imamo najveći broj
12:37
of neurons in the cerebral cortex,
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1472
neurona u moždanoj kori,
12:39
and I think that's the simplest explanation
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1844
i mislim da je to najjednostavnije objašnjenje
12:40
for our remarkable cognitive abilities.
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748884
2013
za naše odlične kognitivne sposobnosti.
12:42
And what is it that we do that no other animal does,
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3227
I što je to što mi radimo, a nijedna druga životinja ne radi,
12:46
and which I believe was fundamental
326
754124
1969
i što vjerujem je bila osnova
12:48
to allow us to reach that large,
327
756093
3083
koja nam je omogućila doseći taj veliki
12:51
largest number of neurons in the cortex?
328
759176
2222
najveći broj neurona u kori?
12:53
In two words, we cook.
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2215
U dvije riječi, mi kuhamo
12:55
No other animal cooks its food. Only humans do.
330
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3566
Nijedna druga životinja ne kuha svoju hranu. Samo ljudi da.
12:59
And I think that's how we got to become human.
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2870
I mislim da smo tako postali ljudi.
13:02
Studying the human brain changed
the way I think about food.
the way I think about food.
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2460
Proučavanje ljudskog mozga je promjenilo način na koji razmišljam o hrani.
13:04
I now look at my kitchen,
333
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1645
Sada gledam svoju kuhinji,
13:06
and I bow to it,
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1470
i poklanjam joj se,
13:07
and I thank my ancestors for coming up
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1705
i zahvaljujem svojim precima što su došli
13:09
with the invention that probably made us humans.
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1900
do otkrića koje nas je vjerojatno učinilo ljudima.
13:11
Thank you very much.
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2132
Hvala vam puno.
13:13
(Applause)
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(Pljesak)
ABOUT THE SPEAKER
Suzana Herculano-Houzel - NeuroscientistSuzana Herculano-Houzel shrunk the human brain by 14 billion neurons -- by developing a new way to count them.
Why you should listen
How many neurons make a human brain? For years, the answer has been (give or take) 100 billion. But neuroscientist Suzana Herculano-Houzel decided to count them herself. Her research approach involved dissolving four human brains (donated to science) into a homogeneous mixture -- in her lab at the Institute of Biomedical Sciences in Rio de Janeiro, they call it "brain soup." She then took a sample of the mix, counted the number of cell nuclei belonging to neurons, and scaled that up. Result: the human brain has about 86 billion neurons, 14 billion fewer than assumed -- but intriguingly, far more than other animals, relative to brain size.
She suggests that it was the invention of cooking by our ancestors -- which makes food yield much more metabolic energy -- that allowed humans to develop the largest primate brain. She's now working on elephant and whale brains to test her hypothesis.
Suzana Herculano-Houzel | Speaker | TED.com