PBS.新星.狗狗的起源与演化（2004）

There's the famous part, which encodes proteins.
但另一部分更为鲜为人知的
Then there's the less-appreciated part,
我觉得那才是关键所在
where I think the real action is,
也就是所谓的"调控"DNA
and this is in the so-called "regulatory" DNA.
它决定DNA编码
It tells the protein coding part of the gene
何时或者何地发生变异
where and when to be active.
就如同基因组的控制软件
It is the software of the genome.
依照莱文所言
According to Levine,
该软件仅凭细微变化
subtle changes in this software
甚至不需改变DNA序列
could produce remarkable diversity
就能产生形态万千的狗狗
and do it without changing the DNA that makes a dog a dog.
所有狗可能都有长腿基因
All these dogs could have the same genes for leg growth,
唯一差别就是 那些基因是否始起作用
the only difference may be in when those genes are turned on and off.
令迈克·莱文等基因学家沮丧的是
The frustration for geneticists like Mike Levine is that,
迄今为止他们仍无法破译"调控"DNA
so far, they haven't been able to crack the code of the regulatory DNA.
我们知道这种DNA存在
We know the DNA exists,
我们知道"调控"DNA决定了
we know that the cis-regulatory DNA controls in detail
基因何时会被激活或抑制的细节
where genes are turned on and off,
在发展与进化过程中都明白
both in development and in evolution,
但我们仍然无法破解这段DNA
but we just don't have a handle on the language of that DNA.
这就如同
It's sort of like
发现了藏宝室的大门却没有钥匙
discovering the Dead Sea scrolls and not knowing Hebrew.
我们需要找到一种
We need to find a language
破译"调控"DNA的语言
to decipher the meaning of the cis-regulatory DNA
否则将永远无法了解基因组的奥秘
if we're ever going to understand the functions of complex genomes
狗和人的都无法了解
such as dog genomes and human genomes.
就算不能破译调整DNA
Even without being able to read the regulatory DNA,
科学家仍然确信
scientists are convinced of
它决定了动物的外形
its importance in determining an animal's physical shape.
那么遗传行为又如何解释呢
But what about inherited behaviors,
譬如有些狗总喜欢把东西拣回来
like the unquenchable desire some dogs have to retrieve?
他们是否也受到"调控"基因影响呢
Could they, too, be influenced by when genes are turned on and off?
生物学家用这一观点来解释查理的行为
It's certainly a part of how biologists explain Charlie's behavior.
举例来说 狗对羊的反映
He has, to say the least, a very different reaction
和他们的祖先狼截然不同
to sheep than his wolf cousins.
对狼来说 羊只是一顿饱餐
Sheep, to a wolf, are dinner on the hoof.
而对查理来说
To Charlie,
羊是需要它保护的对象
sheep are comrades to protect from nasty predators like wolves.
很久以前 这种行为就已建立了
It's a bond he formed early in life.
当时查理还是涉世未深的小狗
When Charlie was a puppy he went through a stage of life
他尤其渴望学到一切新的技能
when he was especially open to new experiences.
这就是所谓的 "社会化进程关键期"
It's called the "critical period of socialization."
所有脊椎动物都有其关键期
All animals, all vertebrates, anyway, have this critical period,
他们在这段时期内认识自己的种群
where the animal learns what species it belongs to.
譬如说在鸟的关键期
Birds, they have a critical period
它们学会了其物种特有的鸣叫
where they learn the species' specific song.
如果你不会它们的鸣叫
If you don't learn the song, then you can't go out there
那你就不能靠它来求偶
and sing the song and get a mate.
所以它们必须学会
So they have to learn it.
而且必须在这段短暂时期内学会
And they can only learn it in this one little window of time.
狗的社会化发展的关键期
Now, dogs' critical period for social development
差不多只有16周左右的时间
is probably about the first 16 weeks.
16周过后
At that point,
其社会化进程学习将会停止
a signal from the genes closes this critical social window.
对狼而言 关键期只有3周
In wolves, that signal comes when they're about three weeks old,
意味着狗有5倍的时间完成社会化
which means dogs have five times as long to form social bonds.
如果一条狗的关键期是在羊群中度过
If a dog grows up in its critical period of socialization in a flock of sheep,
那么它就能与羊融洽相处
then it can socialize with sheep.
同样方法它也能融洽地与人相处
If it grows up in a flock of people, it socializes with people.
这段时期的可塑性相当强
It's very malleable in that kind of way.
基因何时激活和抑制同样也被决定了
When genes are turned on and off may also determine
也决定了各自的特色
why some breeds are so much better
比如有的学会了牧羊
at characteristic activities like herding,
有些则擅长追踪与寻回
tracking and retrieving.
这些都来源于其天生捕猎的本能
All of these have their roots in the instinctive way a wolf hunts.
所有的掠食动物都一样
Every predator hunts in basically the same way.
先从搜寻猎物开始
It starts with "search,"
然后锁定潜在的猎物
which turns into "eye-stalk" when a potential meal is found.
一旦接近猎物 迅速出击
Once close enough, "chase" begins. "
撕咬着扑倒猎物 最后送上致命一击
Grab-bite" brings dinner down, and "kill-bite" finishes the job.
一匹狼 一旦开始了这一顺序
A wolf, once he starts into the sequence,
它就必须从头到尾地执行
he's got to go all the way to the end.
因此它从搜寻一直到锁定目标扑上去
So he goes from the searching to the eye-stalk to the chase,
你绝无可能从中轻易阻止
and you can't say,
不可能对它说 "乖孩子 放松 别过去"
"Look, all right boy, easy, easy, easy—don't go there,"
因为终结羊的性命
because for the wolf it's appetitive;
那是狼饥饿时的天性
at the other end of it is a dead sheep.
而狗的食物则由人类赐予
But dogs get their food from people.
即使是猎犬也没有必要为生存而捕猎
Even hunting dogs like this pointer don't need to hunt for a steady meal.
那些遗传基因里诸如追捕的本能
That means there's no downside if the genetic signal for an instinct
并未言过其实 也从未被削弱
like stalk or chase is exaggerated, weakened,
DNA也从未被完全地改变
or even turned off completely.
因此如果我与它一起
All right, so if I go to the pointer,
它能够帮我搜索猎物
I have him searching, he goes into the eye,
但我并不担心追捕
but I don't care about stalk.
我不希望他去追赶 这明显是个错误
I don't want him to chase, chase is a fault.
它会把鸟赶出去的
I don't want him chasing the bird out of there.
如果你想要寻回犬
If you look at, say, a retriever—
我并不怀疑它们的眼力
I don't care about eye-stalk in a retriever.
我想要获取猎物的方位
I really want the orientation.
希望他们能够帮我追踪
I want them searching for something, and when I find it,
在我发现猎物之后去帮我叼回来
I want them to go right to grab-bite.
这两个阶段总有些矛盾
So those two stages in the middle,
我的目标不是那些
bango, I don't want those.
我只希望他们能把正确的猎物带回来
I just want them to go right to grab-bite.
我希望他们完成致命一击吗
Do I want kill-bite?
不 当寻回犬对猎物使出致命一击
No. And when I get kill-bite in a retriever..
那就叫做 桀骜难驯
that's called "hard mouth."
他会停下来吃了它 你知道吗
He stops and eats it, you know?
每个猎人最不希望的场景莫过于
Every retriever man's worst scenario of
突然之间猎狗停下来把猎物吃掉了
all of a sudden the dog stops and eats the bird.
跟踪 指示 寻回 牧群
Tracking, pointing, retrieving, herding,
我们今天用以评价狗勤勉作为的
many of the behaviors we most value in dogs today,
都只是狼生存的基本技能
are simply aspects of what a wolf does to survive.
人类使用狗追踪猎物的气味
Give a dog a job, say, to follow a scent,
奖赏那些最出色的狗
reward the ones that do it best,
历经上千年的传承 这些本能产生了进化
and over thousands of generations a distinct behavior will evolve.
结果产生了地球上种类最繁多的哺乳动物
The result is the most diverse mammal on earth.
全球共有囊括400种以上超过4亿条狗
There's more than 400 different dog breeds and more than 400 million dogs.
那比狼的数量高出数千倍
That's thousands of times more dogs than wolves.
在进化过程中狗是真正的赢家
In evolutionary terms, the dog is a real winner.
有些狗狗更是中了头彩
And some dogs have hit the jackpot,
它们有幸享受
like the lucky few who are regulars
曼哈顿犬类日托中心的服务
at this Manhattan doggy day care center.
它们能在这里交朋友 游泳
Here they can hang with friends, swim in the pool,
享用美味饼干和个性化高级护理
enjoy biscuits on demand and the attentions of a personal stylist.
他们甚至可以去旅行
They even take field trips.
有时我们把狗狗带到南安普顿
Sometimes we have... we take the dogs to Southampton.
在11月底我们还将举♥行♥一次巡游
We're going to have a cruise at the end of November.
曾经的工作犬基本都成了宠物
Once primarily working animals, dogs today are mostly pets.
比起他们的行为和工作能力
They're frequently chosen more for what they look like than
他们的长相才是其被宠爱的原因
what they can do or how they behave.
但是对于外观的过分追求也有弊端
But a preoccupation with appearance is not without consequences.
所有纯种狗都是强度育种的结果
All purebred dogs are products of intensive breeding,
而每年越来越多的纯种犬
and every year more and more of them
正在遭受日益增长的遗传疾病的威胁
suffer from an ever-growing list of genetic diseases.
有趣的是
Interestingly,
狗的疾病和宠物地位
the disease problem and the dog's elevated place in our lives
都可追溯到维多利亚时期的英格兰
can both be traced to Victorian England.
当时崛起的中产阶级为了炫耀
A growing middle class, looking for ways to show they've arrived,
模仿有钱人开始领养宠物