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Until the advent of molecular genetics,
在分子遗传学出现前
archaeology had few firm answers.
考古学对很多问题都给不出确定的答案
All you have to play with are the bones
你能够做的只有研究动物的骨头
and so when you look at the bones, if you don't have
因此当你观察那些骨头的时候
a very small flat-faced round-headed pug in
如果考古学中没有出现过
the archaeological record,
扁脸圆头哈巴狗的化石
you don't know where that came from.
你就不知道它从何而来
Those are questions that
那些问题在遗传学出现之前
before genetics you really couldn't answer.
真的是难以回答的
To unravel the evolutionary origins of dogs,
为了发现犬类的进化原型
molecular Geneticists compared DNA
分子遗传学家比对了
from dogs with that of their wild relatives.
狗与其野生亲属的DNA
Specifically, they looked at mitochondrial dna sequences
他们目标明确的着手于线粒体的DNA顺序
Which are passed unchanged down the maternal line.
这些DNA完全遗传于母系
What's so useful for scientists
随着时间的推移线粒体DNA只改变了
is that mitochondrial DNA changes little over time
很小一部分 这对科学家来说非常有用
And so acts as a kind of signature
这就如同一个签名
left by an animal's ancestors.
遗传自某类动物的祖先
Those markers in domestic dogs show them to be much more
从这些家狗的线粒体DNA中可以发现
closely related to grey wolves
和其他物种对比
than they are to any other species.
他们与灰狼的基因更加相似
There's no admixture
这里没有任何的基因的糅合
so we never see a mitochondrial signature of saying
我们从未在家狗身上发现任何存在于
An african wild dog, jackal or coyote in a domestic dog.
非洲野狗 豺 山狗身上的线粒体DNA
Of thousands upon thousands of mitochondrial DNA
在成千上万的线粒体DNA中
that has been extracted from domestic dogs,
那些从驯养狗身上萃取下来的DNA
every single one of them just looks just like a grey wolf.
每一部分都与灰狼的DNA非常接近
