TEDGlobal 2013
Suzana Herculano-Houzel: What is so special about the human brain?
苏珊娜·郝库蓝诺-赫佐尔: 人类大脑最特别的地方在哪里？
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人类的大脑是一个迷 -- 对于我们的身体来说，它是出奇地大。它的重量和那一个奇形怪状的密集的大脑皮层消耗了大量的能量。但是：为什么？神经学家苏珊娜带上她的侦探帽，带领我们探索这个神秘的大脑。通过制作“大脑汤剂”，她得到了一个惊人的结论。
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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对于人类的大脑来说，什么是最特别的？
00:15
Why is it that we study other animals
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我们为什么要研究其他的动物？
00:17
instead of them studying us?
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而不是他们研究我们？
00:19
What does a human brain have or do
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有没有什么是人类大脑可以做的
00:21
that no other brain does?
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而其他的大脑不能做的？
00:23
When I became interested
in these questions about 10 years ago,
in these questions about 10 years ago,
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十年前，我对这些问题产生兴趣
00:26
scientists thought they knew
what different brains were made of.
what different brains were made of.
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科学家认为他们知道大脑不同的组成部分
00:28
Though it was based on very little evidence,
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即使那些都是基于一些非常小的证据，
00:30
many scientists thought that all mammalian brains,
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很多科学界认为所有的哺乳动物的大脑，
00:32
including the human brain,
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包括人类的大脑
00:34
were made in the same way,
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是由同样的东西组成，
00:35
with a number of neurons that was always
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一系列的神经元和大脑的大小
00:37
proportional to the size of the brain.
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总是成为成正比
00:39
This means that two brains of the same size,
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这个以为着，两个同样大小的大脑
00:41
like these two, with a respectable 400 grams,
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就看这两个，有大概400克，
00:45
should have similar numbers of neurons.
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应该有同样数量的神经元
00:47
Now, if neurons are the functional
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如果我们说神经元是大脑
00:49
information processing units of the brain,
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功能信息处理的单位
00:52
then the owners of these two brains
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然后，这些两个大脑各自的拥有者
00:54
should have similar cognitive abilities.
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应该有的相近的认知能力。
00:56
And yet, one is a chimp,
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然而，其中一个是黑猩猩，
00:59
and the other is a cow.
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和另一种是一头母牛。
01:01
Now maybe cows have a really rich
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现在也许牛有很丰富的
01:04
internal mental life and are so smart
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精神生活，并且很聪明
01:06
that they choose not to let us realize it,
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他们选择不会让我们意识到这一点，
01:10
but we eat them.
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但我们吃他们。
01:11
I think most people will agree
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我想大多数人会同意
01:13
that chimps are capable of much more complex,
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相比于牛来说，黑猩猩具有更加复杂
01:15
elaborate and flexible behaviors than cows are.
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和细节，以及灵活的行为。
01:18
So this is a first indication that the
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所以这是第一个征兆显示
01:20
"all brains are made the same way" scenario
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"所有的大脑的构成方式都是一样的"
01:22
is not quite right.
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不是特别正确的。
01:24
But let's play along.
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我们不妨继续这个比喻
01:25
If all brains were made the same way
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如果所有的大脑由相同的方式组成
01:27
and you were to compare animals
with brains of different sizes,
with brains of different sizes,
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你要将大脑大小不同的动物拿来做比较,
01:30
larger brains should always have more neurons
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大一点的大脑对于小一点的大脑来说
01:32
than smaller brains,
and the larger the brain,
and the larger the brain,
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应该具有等多的神经元，
并且越大的大脑，
并且越大的大脑，
01:34
the more cognitively able its owner should be.
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它的主人应该更有认知能力。
01:37
So the largest brain around should also be
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所以最大的脑应该具有
01:39
the most cognitively able.
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最好的认知能力。
01:42
And here comes the bad news:
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这里有个坏消息要说：
01:43
Our brain, not the largest one around.
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我们的大脑，不是最大的一个。
01:46
It seems quite vexing.
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看起来相当棘手。
01:47
Our brain weighs between 1.2 and 1.5 kilos,
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我们的大脑重量 1.2 和 1.5 公斤之间
01:50
but elephant brains weigh between four and five kilos,
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但大象脑子称之间四、 五公斤
01:54
and whale brains can weigh up to nine kilos,
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鲸鱼大脑可重达 9 公斤
01:56
which is why scientists used to resort to saying
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这就是为什么科学家们用来诉诸说
02:01
that our brain must be special
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我们的大脑肯定是非常特别地
02:03
to explain our cognitive abilities.
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来解释我们的认知能力。
02:06
It must be really extraordinary,
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它必须是真的非同寻常，
02:09
an exception to the rule.
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一个例外情况。
02:11
Theirs may be bigger, but ours is better,
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他们的大脑可能会更大，但我们的更好，
02:14
and it could be better, for example,
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并且我们的可以变得更加好，例如，
02:16
in that it seems larger than it should be,
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在这似乎比它应该更大
02:18
with a much larger cerebral cortex
than we should have
than we should have
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与很多大大脑皮层比我们应该有的
02:21
for the size of our bodies.
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对于我们的身体的大小。
02:22
So that would give us extra cortex
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因此，这样将会给我们额外皮质
02:24
to do more interesting things
than just operating the body.
than just operating the body.
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去做更多有趣的事情，而不是只主管我的身体。
02:27
That's because the size of the brain
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这是因为大脑的大小
02:29
usually follows the size of the body.
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通常遵循身体的大小。
02:31
So the main reason for saying that
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所以说这句话的主要原因就是
02:33
our brain is larger than it should be
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我们的大脑已经比它应有的大小大出好多了
02:35
actually comes from comparing ourselves
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其实是来自于比较我们自己
02:37
to great apes.
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和巨猿。
02:39
Gorillas can be two to three times larger than we are,
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大猩猩可以是比我们大两到三倍
02:41
so their brains should also be larger than ours,
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因此，他们的大脑也应该比我们的大
02:44
but instead it's the other way around.
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但相反，它的大脑比我们的小。
02:46
Our brain is three times larger than a gorilla brain.
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我们的大脑是比大猩猩脑大三倍。
02:49
The human brain also seems special
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人类的大脑似乎也很特别
02:51
in the amount of energy that it uses.
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在于它使用的能源的量。
02:53
Although it weighs only two percent of the body,
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虽然它的重量只有全身的2%，
02:56
it alone uses 25 percent of all the energy
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但是它单独使用
02:59
that your body requires to run per day.
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你身体每天所需能量的25%
03:02
That's 500 calories out of a total of 2,000 calories,
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2000卡路里里面的500卡路里
03:05
just to keep your brain working.
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仅仅只是为了让你的大脑的工作。
03:07
So the human brain is larger than it should be,
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所以，人类的大脑已经比应有的大小大出很多了
03:10
it uses much more energy than it should,
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它消耗了更加多的能量，对于他应该消耗的来说
03:12
so it's special.
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所以它很特殊。
03:14
And this is where the story started to bother me.
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这是这个故事开始让我感到疑惑。
03:16
In biology, we look for rules
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在生物学中，我们发现规则
03:18
that apply to all animals and to life in general,
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一般情况下，适用于所有的动物和生活
03:21
so why should the rules of evolution
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那么为什么进化的规则
03:23
apply to everybody else but not to us?
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应用到了其他生物，但不是我们？
03:26
Maybe the problem was with the basic assumption
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也许这个问题是一个基础的假设
03:29
that all brains are made in the same way.
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所有的大脑都是由相同的方式组成。
03:30
Maybe two brains of a similar size
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也许两个大小相似的大脑
03:32
can actually be made of
very different numbers of neurons.
very different numbers of neurons.
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实际上可以由数目不同的神经元组成。
03:35
Maybe a very large brain
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也许是一个非常大的大脑
03:36
does not necessarily have more neurons
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不一定需要具有更多的神经元
03:38
than a more modest-sized brain.
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对于一个更具规模适度的大脑。
03:40
Maybe the human brain
actually has the most neurons
actually has the most neurons
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也许，相比于其他大脑来说，人类的大脑具有
03:43
of any brain, regardless of its size,
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最多的神经元，无论其规模大小，
03:46
especially in the cerebral cortex.
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尤其是在大脑皮质中。
03:48
So this to me became
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所以这对我来说成为了
03:50
the important question to answer:
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对于这个答案来说最重要的问题
03:51
how many neurons does the human brain have,
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人类大脑有多少神经元
03:54
and how does that compare to other animals?
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和其他动物比较起来怎样？
03:56
Now, you may have heard or read somewhere
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现在，您可能会听到或读到过
03:59
that we have 100 billion neurons,
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我们有 1000 亿个神经元
04:01
so 10 years ago, I asked my colleagues
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10 年前，我就问我的同事们
04:03
if they knew where this number came from.
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他们是否知道这个数字是从哪里来的。
04:05
But nobody did.
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但没人知道。
04:06
I've been digging through the literature
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我通过深入细致的研究文献
04:08
for the original reference for that number,
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试图找出该数字的原始参考
04:10
and I could never find it.
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但我找不到它。
04:11
It seems that nobody had actually ever counted
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这似乎其实没有人去真正的数过
04:14
the number of neurons in the human brain,
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人类大脑里面的神经元数量，
04:16
or in any other brain for that matter.
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或者其他任何的大脑里面神经元的数量。
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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所以我想出了我自己的方式来统计大脑里面的细胞，
04:22
and it essentially consists of
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它最重要的一个步骤是
04:24
dissolving that brain into soup.
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那大脑溶解在试剂里。
04:27
It works like this:
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它的工作方式：
04:29
You take a brain, or parts of that brain,
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你带一个大脑或部分的大脑，
04:32
and you dissolve it in detergent,
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让它溶化在洗涤剂里，
04:34
which destroys the cell membranes
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洗涤剂会破坏细胞膜
04:35
but keeps the cell nuclei intact,
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但保持细胞核不变，
04:38
so you end up with a suspension of free nuclei
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所以你最终会看到细胞核悬浮
04:41
that looks like this,
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看起来像这样，
04:43
like a clear soup.
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像一碗清汤。
04:44
This soup contains all the nuclei
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这汤包含所有细胞核
04:46
that once were a mouse brain.
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曾经是一个老鼠的大脑。
04:48
Now, the beauty of a soup is that because it is soup,
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现在，这个液体的魅力在于因为它是液体，
04:51
you can agitate it and make those nuclei
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可以摇晃它，并使这些细胞核
04:54
be distributed homogeneously in the liquid,
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在液体中均匀分布
04:56
so that now by looking under the microscope
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所以，现在通过在显微镜下观察
04:58
at just four or five samples
of this homogeneous solution,
of this homogeneous solution,
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只需四个或五个
这种细胞核均匀分布的样本
这种细胞核均匀分布的样本
05:02
you can count nuclei, and therefore tell
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你可以数数原子核，并能够知道
05:05
how many cells that brain had.
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有多少脑细胞了。
05:06
It's simple, it's straightforward,
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这样很简单，非常直接，
05:08
and it's really fast.
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并且，这样的速度也很快。
05:09
So we've used that method to count neurons
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所以我们使用了这种方法来计数神经元
05:11
in dozens of different species so far,
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目前为止计数了几十个不同的物种，
05:14
and it turns out that all brains
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结果发现，所有的大脑
05:15
are not made the same way.
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是由不同的方式组成的。
05:18
Take rodents and primates, for instance:
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以啮齿类动物和灵长类动物为例：
05:20
In larger rodent brains, the average size
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在大一些的啮齿类动物大脑里，
05:22
of the neuron increases,
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神经元的平均尺寸在增加，
05:24
so the brain inflates very rapidly
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所以，大脑非常迅速地膨胀
05:27
and gains size much faster than it gains neurons.
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尺寸增长比获得神经元更加快
05:30
But primate brains gain neurons
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但灵长类动物的大脑得到神经元
05:32
without the average neuron becoming any larger,
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而不需要神经元平均尺寸增大
05:34
which is a very economical way
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这是一种非常经济的方法
05:35
to add neurons to your brain.
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在你大脑里添加神经元
05:37
The result is that a primate brain
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结果是灵长类动物的大脑
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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和啮齿动物相同大小的脑相比, 总有更多的神经元
05:42
and the larger the brain,
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和大脑越大
05:44
the larger this difference will be.
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这种差异性將越來越大
05:46
Well, what about our brain then?
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那么,我们的大脑又是如何呢?
05:48
We found that we have, on average,
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我们发现我们平均有
05:50
86 billion neurons,
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860 亿个神经元
05:51
16 billion of which are in the cerebral cortex,
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其中有 160 亿个存在于大脑皮质里
05:54
and if you consider that the cerebral cortex
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而且如果你认为大脑皮质
05:56
is the seat of functions like
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是下列功能的基础，
06:00
awareness and logical and abstract reasoning,
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意识,逻辑和抽象推理，
06:03
and that 16 billion is the most neurons
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那么，这160 亿个神经元
06:06
that any cortex has,
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对大脑皮质来说是最重要的
06:08
I think this is the simplest explanation
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我想这是最简单的說明
06:10
for our remarkable cognitive abilities.
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对于我们卓越的认知能力。
06:13
But just as important is what
the 86 billion neurons mean.
the 86 billion neurons mean.
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但,就和 860 亿神经元的意义一样重要
06:16
Because we found that the relationship
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因为我们发现了
06:18
between the size of the brain
and its number of neurons
and its number of neurons
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大脑的大小和其神经元数目之间的关联
06:20
could be described mathematically,
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是可以用数学模型来计算的
06:22
we could calculate what a human brain
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我们可以计算出人类大脑
06:24
would look like if it was made like a rodent brain.
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如果被作成像是一个啮齿类动物的大脑会如何。
06:27
So, a rodent brain with 86 billion neurons
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所以，有着 860 亿神经元的啮齿类动物大脑
06:30
would weigh 36 kilos.
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将重 36 公斤。
06:33
That's not possible.
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那是不可能的。
06:35
A brain that huge would be crushed
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巨大的大脑將会被
06:37
by its own weight,
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它自己本身的重量所挤压，
06:38
and this impossible brain would go
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这个不可能的大脑將会适用于
06:40
in the body of 89 tons.
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一个89吨的身体 。
06:44
I don't think it looks like us.
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我不认为它看起来跟我们一样。
06:46
So this brings us to a very important
conclusion already,
conclusion already,
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因此，这已经带給我们的一个非常重要的结论，
06:48
which is that we are not rodents.
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我们不是啮齿类动物。
06:51
The human brain is not a large rat brain.
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人类的大脑不是一个大老鼠的大脑。
06:54
Compared to a rat, we might seem special, yes,
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和一只老鼠相比，我们看起来可能特别些，是的
06:57
but that's not a fair comparison to make,
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但这样的比较不公平，
06:59
given that we know that we are not rodents.
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我们知道我们不是啮齿类动物。
07:01
We are primates,
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我们是灵长类动物，
07:02
so the correct comparison is to other primates.
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因此和其他的灵长类动物做正确的比较。
07:05
And there, if you do the math,
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這里还有，如果你自己来算一下，
07:06
you find that a generic primate
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你会发现一般的的灵长类动物
07:09
with 86 billion neurons
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有着860 亿神经元
07:11
would have a brain of about 1.2 kilos,
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3003
将会有一个约 1.2 公斤的大脑
07:14
which seems just right,
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这似乎刚刚好，
07:16
in a body of some 66 kilos,
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1972
在大约66 公斤身体中，
07:18
which in my case is exactly right,
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在我的研究是完全正确的
07:21
which brings us to a very unsurprising
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我们对此一点儿也不惊讶
07:23
but still incredibly important conclusion:
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但这仍是令人难以置信的重要结论：
07:26
I am a primate.
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我是灵长类动物。
07:28
And all of you are primates.
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而且,你们全部都是灵长类动物。
07:30
And so was Darwin.
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达尔文也是。
07:32
I love to think that Darwin
would have really appreciated this.
would have really appreciated this.
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我认为达尔文会很欣赏这个研究结论。
07:35
His brain, like ours,
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他的大脑，像我们一样，
07:37
was made in the image of other primate brains.
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和其它灵长类动物的大脑一样。
07:41
So the human brain may be remarkable, yes,
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2302
所以，人类的大脑可能是显著的,是的
07:43
but it is not special in its number of neurons.
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2781
但它特别之处不在于其神经元的数目。
07:46
It is just a large primate brain.
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它只是一个大的灵长类动物的大脑。
07:48
I think that's a very humbling and sobering thought
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我想这是个非常谦卑和发人深省的思考
07:51
that should remind us of our place in nature.
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提醒了我们在自然界的位置。
07:54
Why does it cost so much energy, then?
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为什么我们的大脑消耗这么大的能量，然后呢？
07:56
Well, other people have figured out
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有些人已经想通了，
07:58
how much energy the human brain
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人类的大脑能消耗多少能量
07:59
and that of other species costs,
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1407
和其他物种的大脑消耗多少能量
08:01
and now that we knew how many neurons
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而现在,我们知道
08:02
each brain was made of, we could do the math.
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每个大脑中有多少神经元，我们可以算一算。
08:05
And it turns out that both human
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结果是,人类
08:07
and other brains cost about the same,
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2823
和其他物种的大脑消耗相同的能量
08:09
an average of six calories
per billion neurons per day.
per billion neurons per day.
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平均每日，每十亿个神经元消耗六个卡路里的热量。
08:13
So the total energetic cost of a brain
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2139
所以一个大脑全部精力的消耗
08:15
is a simple, linear function
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2034
是简单的，线性函数
08:17
of its number of neurons,
211
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1709
可计算其神经元的数目
08:19
and it turns out that the human brain
212
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结果发现，人类的大脑
08:21
costs just as much energy as you would expect.
213
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3841
消耗的能量就跟你预期的一样
08:25
So the reason why the human brain
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2091
所以，为什么人类的大脑
08:27
costs so much energy is simply because
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1672
消耗如此多的能量的原因容易理解，
08:28
it has a huge number of neurons,
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1983
因为它有大量的神经元，
08:30
and because we are primates
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1485
还有,因为我们是灵长类动物
08:32
with many more neurons for a given body size
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在一个特定大小的身体里,
08:34
than any other animal,
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1522
人类比任何其他的动物，有着更多的神经元
08:36
the relative cost of our brain is large,
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3540
我们的大脑的相对消耗量是很大的，
08:39
but just because we're primates,
not because we're special.
not because we're special.
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3001
但只是因为我们是灵长类动物，不是因为我们是特別的。
08:42
Last question, then:
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1190
最后一个问题，
08:44
how did we come by this
remarkable number of neurons,
remarkable number of neurons,
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我们为什么有数量巨大的神经元，
08:47
and in particular, if great apes
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1900
特别是，如果巨猿
08:49
are larger than we are,
225
517178
1555
比我们更大，
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
那为什么他们沒有一个有着更多神经细胞,比我们还大的大脑呢?
08:54
When we realized how much expensive it is
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2090
当我们意识到这个有多珍貴,
08:56
to have a lot of neurons in the brain, I figured,
228
524588
2333
在大脑中有大量的神经元，我想，
08:58
maybe there's a simple reason.
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2003
可能有一个简单的原因。
09:00
They just can't afford the energy
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1683
他们只是不能负担
09:02
for both a large body
and a large number of neurons.
and a large number of neurons.
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2950
一个大型的身体以及多量的神经细胞共存所需的能量。
09:05
So we did the math.
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1429
所以我们算过
09:06
We calculated on the one hand
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1600
一方面，我们计算着
09:08
how much energy a primate gets per day
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1941
一个灵长类动物每一天获取多少能量
09:10
from eating raw foods,
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1350
借由吃生的食物，
09:11
and on the other hand, how much energy
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2037
另一方面，有多少能量
09:13
a body of a certain size costs
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1764
在一个特定大小的身体中消耗
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
和有多少能量在含有特定数量神经元的大脑中消耗
09:19
and we looked for the combinations
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547065
1489
然后我们找到一个结合
09:20
of body size and number of brain neurons
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身体尺寸和大脑神经元数目
09:22
that a primate could afford
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灵长类动物能夠负担得起
09:24
if it ate a certain number of hours per day.
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如果它每天花一定数量的时间在吃上面。
09:26
And what we found is that
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1816
然后, 我们发现到
09:28
because neurons are so expensive,
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1712
因为神经细胞太珍貴了，
09:30
there is a tradeoff between
body size and number of neurons.
body size and number of neurons.
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3370
有一个权衡出先在身体大小和神经元的數量之间。
09:33
So a primate that eats eight hours per day
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2951
所以, 一个灵长类动物每天吃八个小时
09:36
can afford at most 53 billion neurons,
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3024
能够负担最多 530 亿神经元，
09:39
but then its body cannot be any bigger
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1727
但是，它的身体不能
09:41
than 25 kilos.
249
569383
1954
超过25 公斤。
09:43
To weigh any more than that,
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1701
任何比这更重的重量
09:45
it has to give up neurons.
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1769
它必须放弃一些神经细胞。
09:46
So it's either a large body
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2653
所以,它不是一个庞大身体
09:49
or a large number of neurons.
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1495
就是一个大数量的神经元。
09:50
When you eat like a primate,
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当你吃的像灵长类动物时，
09:52
you can't afford both.
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2236
你不能负担任何一方。
09:54
One way out of this metabolic limitation
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1964
一个方法超出此种代谢限制是
09:56
would be to spend even more hours per day eating,
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3401
每一天花更多的时间在吃饭上面，
09:59
but that gets dangerous,
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587921
1363
但是，这样是很危险的
10:01
and past a certain point, it's just not possible.
259
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2719
某种程度上，它是不可能发生的。
10:04
Gorillas and orangutans, for instance,
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1537
大猩猩和红毛猩猩，例如，
10:05
afford about 30 billion neurons
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1923
能夠负担约 300 亿个神经元
10:07
by spending eight and a half hours per day eating,
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2966
它们每天花八个半小时吃饭，
10:10
and that seems to be about as much as they can do.
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3116
这似乎是它们所能做的一切。
10:13
Nine hours of feeding per day
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1791
9 个小时的每日饲喂
10:15
seems to be the practical limit for a primate.
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3271
是灵长类动物的实际限制。
10:18
What about us?
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那我们呢?
10:20
With our 86 billion neurons
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1600
根据我们的860 亿神经元
10:21
and 60 to 70 kilos of body mass,
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3035
和 60 到 70 公斤的体重，
10:25
we should have to spend over nine hours
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3561
我们应该要花超过九个小时
10:28
per day every single day feeding,
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3575
每天在吃饭上
10:32
which is just not feasible.
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2039
这是不可行的。
10:34
If we ate like a primate,
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1834
如果我们像灵长类动物一样吃，
10:36
we should not be here.
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2253
我们不应该在这里。
10:38
How did we get here, then?
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2127
我们怎么在这里呢？
10:40
Well, if our brain costs just as much energy
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2735
好吧，如果我们的大脑消耗的能量跟他
10:43
as it should, and if we can't spend
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631157
1723
应该所消耗的一致，并且如果我们不能把每天
10:44
every waking hour of the day feeding,
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3674
醒着的时间都花在吃饭上，
10:48
then the only alternative, really,
278
636554
1911
然后这个唯一的选择，真的，
10:50
is to somehow get more energy
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638465
1958
是以某种方式
10:52
out of the same foods.
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1953
从相同的食品上获取更多的能量。
10:54
And remarkably, that matches exactly
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3800
引人注目的是，这和我们的祖先
10:58
what our ancestors are believed to have invented
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3037
早已发现的完全匹配
11:01
one and a half million years ago,
283
649213
1839
在一百五十万年前，
11:03
when they invented cooking.
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2782
他们发明了烹饪。
11:05
To cook is to use fire
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653834
1970
要做饭就得使用火
11:07
to pre-digest foods outside of your body.
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3800
在食物进入你身体前预先消化食物。
11:11
Cooked foods are softer, so they're easier to chew
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2606
煮熟的食物比较软，所以他们更容易嚼烂
11:14
and to turn completely into mush in your mouth,
288
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2563
在你的嘴里完全粉碎
11:16
so that allows them to be completely digested
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2152
这就使他们能够完全被消化
11:18
and absorbed in your gut,
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1436
并且被你的肠道所吸收，
11:20
which makes them yield much more
energy in much less time.
energy in much less time.
291
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3655
这使得它们在更少的时间内带来更多能源。
11:24
So cooking frees time for us to do
292
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2489
所以烹饪让我们有更多的时间，
11:26
much more interesting things with our day
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2062
去用我们的神经元
11:28
and with our neurons
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1480
做更多有趣的事情
11:30
than just thinking about food,
295
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1905
而不是只想着食物，
11:31
looking for food, and gobbling down food
296
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1704
寻找食物，并吞噬下食物
11:33
all day long.
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1225
花去整整一天。
11:34
So because of cooking, what once was
298
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2499
所以由于烹饪，曾是
11:37
a major liability, this large,
299
685380
2353
一个沉重的负担，这个大，
11:39
dangerously expensive brain with a lot of neurons,
300
687733
3033
且极其昂贵的，有着一大堆神经元的大脑，
11:42
could now become a major asset,
301
690766
2036
现在能够成为一项重要资产，
11:44
now that we could both afford
the energy for a lot of neurons
the energy for a lot of neurons
302
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3251
现在，我们可以为给予神经元提供能量
11:48
and the time to do interesting things with them.
303
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2503
并且把时间用在去做一些有趣的事情。
11:50
So I think this explains why the human brain
304
698559
1974
因此，我认为这就解释了为什么人类的大脑
11:52
grew to become so large so fast in evolution,
305
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3240
在进化过程中增长如此之快，
11:55
all of the while remaining just a primate brain.
306
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3897
当所有剩余的只是一个灵长类动物的大脑。
11:59
With this large brain now affordable by cooking,
307
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2774
与这么大的大脑现在可以负担地起烹饪，
12:02
we went rapidly from raw foods to culture,
308
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2913
我们去迅速地进步着，从生食到文化，
12:05
agriculture, civilization, grocery stores,
309
713357
2606
农业、 文明、 杂货店、
12:07
electricity, refrigerators,
310
715963
1625
电力、 冰箱、
12:09
all of those things that nowadays
311
717588
1607
所有这些事物，现今
12:11
allow us to get all the energy we need
312
719195
2042
使我们能够得到我们需要的所有能量
12:13
for the whole day in a single sitting
313
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2782
一整天所需的所有能量
12:16
at your favorite fast food joint.
314
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2954
来自于你最喜欢的快餐食品。
12:18
So what once was a solution
315
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2437
所以曾是一种解决办法
12:21
now became the problem,
316
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1699
现在成为了这一问题，
12:23
and ironically, we look for the solution in raw food.
317
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5517
讽刺的是，我们在生食中寻找解决方案。
12:28
So what is the human advantage?
318
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2556
那么人类的优势是什么？
12:31
What is it that we have
319
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1503
我们有什么东西
12:32
that no other animal has?
320
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2535
是其他动物没有的吗？
12:35
My answer is that we have the largest number
321
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2348
我的答案是我们有最大数量
12:37
of neurons in the cerebral cortex,
322
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1472
神经元存在于大脑皮层中，
12:39
and I think that's the simplest explanation
323
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1844
并且我认为这能最简单地解释
12:40
for our remarkable cognitive abilities.
324
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2013
为什么我们有卓越的认知能力。
12:42
And what is it that we do that no other animal does,
325
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3227
还有就是我们做了什么是没有其他动物做的，
12:46
and which I believe was fundamental
326
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1969
我认为
12:48
to allow us to reach that large,
327
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3083
使我们能够达到这么多的，
12:51
largest number of neurons in the cortex?
328
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2222
最多数量的神经元存在于大脑皮质中的基本原因是
12:53
In two words, we cook.
329
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2215
两个词，我们做饭。
12:55
No other animal cooks its food. Only humans do.
330
763613
3566
没有其他动物烹饪它们的食物。只有人类才做。
12:59
And I think that's how we got to become human.
331
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2870
而且我认为，这就是我们是怎么成为人类的。
13:02
Studying the human brain changed
the way I think about food.
the way I think about food.
332
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2460
研究人类大脑改变我对食物的想法。
13:04
I now look at my kitchen,
333
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1645
现在我看看自己的厨房，
13:06
and I bow to it,
334
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1470
然后我向它鞠躬，
13:07
and I thank my ancestors for coming up
335
775624
1705
然后我谢谢我的祖先想到
13:09
with the invention that probably made us humans.
336
777329
1900
这个有可能使我们成为人类的发明。
13:11
Thank you very much.
337
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2132
谢谢。
13:13
(Applause)
338
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6353
（掌声）
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