地平线系列：失落的部族（2016）

we are very closely related, right?
现代人类与尼安德特人的差异并不大
Modern humans and Neanderthals are not that different from one another,
因此很难
which makes it really hard
发现有趣的差异点
to work out where are the interesting differences.
所以我们掩盖并
And so what we do is, instead, we mask out,
移除人人相同的部分
we remove all the sites where everyone is the same.
只观察个体与参照基因组有差异的部分
And we only look at the sites where individuals differ from the referenced genome.
现在就能看出丹尼索瓦人和尼安德特人
And so what you see here now is the Neanderthals and the Denisovan
在这儿 这儿 那儿 还有那部分
carry a difference from the modern human reference
与当今人类的参考值不同
at this position and here and there and there.
这些不同之处
And some of those differences
有的在许多群体中都存在
are shared by a number of populations,
包括非洲人
including the African individuals.
而一些不同之处
And some of those differences
却只在少数人身上才有
are shared just by a few individuals,
看这儿 这儿 和这儿
so here, and there, and there.
这些人的基因组证明
The genomes of certain individuals contained evidence
我们流浪的祖先们跟尼安德特人繁衍后代
that our wandering ancestors bred with Neanderthal tribes
这些后代存活下来
and had offspring who survived,
并世代传递他们的基因
passing on their genes down the generations.
这些证据不单存在于几个人身上
And it wasn't just evident in a couple of individuals.
我们研究了非洲人
When we went through the genomes of Africans
欧洲人和亚洲人的基因组
and of Europeans and Asians,
计算每个人种的基因组里有多少DNA碱基对
and counted how many DNA bases
同尼安德特人的基因组相匹配
in each of the genomes matched the Neanderthal genome,
发现除非洲人以外的所有种群
we saw very consistently that all the groups outside of Africa
都比非洲人保留更多尼安德特人的DNA
shared more Neanderthal DNA than the groups inside of Africa.
拥有非洲血统的人
People with African heritage
普遍没有尼安德特人的DNA
don't generally have Neanderthal DNA.
但其他人基本上都有
But virtually everyone else does.
包括我
Including me.
我分♥析♥了自己的基因组
Well, I've had my own genome analysed
我拥有2.7%的尼安德特人基因
and I am 2.7% Neanderthal.
有趣的是
And what is interesting is that
我的这点尼安德特人DNA
my bit of Neanderthal DNA will be different
跟其他人的尼安德特人DNA不一样
to the bit of Neanderthal DNA in another person's genome.
除了非洲人
All people whose roots are outside Africa
所以人都有一点尼安德特人的DNA
carry a bit of Neanderthal DNA.
每人平均携带1%到2%
On average, each person carries somewhere between 1% and 2%.
再来看看现在不同人携带的不同基因片段
If we now look at these different pieces that different people carry today,
今天有多少尼安德特基因组
how much of the Neanderthal genome is still running around today
仍存在于不同个体中
on two legs in different individuals?
它们加起来有多少
How much do we get if we add it up?
而评判标准尚未定型
And the jury is still a bit out on that.
但如今人们身上至少仍存在
But in the order of at least half of the Neanderthal genome
大约一半的尼安德特基因组
still exists today in people.
分♥析♥的人群越多
And that number just keeps rising,
这一数值就越大
the more people they analyse.
难以置信的是
It's incredible to think that
今天仍有约一半的尼安德特基因
around about half the Neanderthal genome
好好的活在我们身上
is still alive and well in us today.
往前推十年
And going back just ten years ago,
我们都不知道有人会有尼安德特人的DNA
we had no idea that any of us had Neanderthal DNA.
现在我们知道几乎每个
Now we know that practically everybody
不是非裔的人
of predominantly non-African heritage
基因组里都含有尼安德特人的DNA
has Neanderthal DNA in their genome.
我们把它理解为
We interpreted that to mean
尼安德特人和那些人的祖先
that the mixture from the Neanderthals into the ancestors of those individuals
是很早之前结合的
had to have been very early.
差不多就是他们离开非洲的时间
At the point very close to when they exited Africa,
也许在中东的某个地方
perhaps somewhere in the Middle East,
当他们仍是一个独♥立♥种群的时候
when they were still a single population.
之后随着他们向外迁徙
And then as they spread out,
他们把尼安德特人的DNA带到各个地方
they carry with them that Neanderthal DNA to wherever they go.
丹尼索瓦人的DNA也能在现代人身上找到
And Denisovans also left their mark in the DNA of living people.
有的多有的少
Some more than others.
举个例子 如果你的祖先是
So if your origins are in
巴布亚新几内亚人或者土著澳大利亚人
Papua New Guinea or aboriginal Australians, for example,
他们大约有5%的DNA来自于丹尼索瓦人
they have in the order of 5% of their DNA from Denisovans,
比他们或欧洲人所拥有的尼安德特人基因
so three or four times more than they have,
还要多个三四倍
or people in Europe would have, from Neanderthals.
亚洲人身上也能找到丹尼索瓦人的DNA
Traces of Denisovan DNA can also be found in populations
在印度 喜马拉雅山脉和中国都有
across Asia, in India, the Himalayas and China,
据估计现仍存在的丹尼索瓦人基因组
and it's estimated that there could be as much as 60-80%
可能多达60-80%
of the Denisovan genome still in existence,
遍布全球各个人种
spread around the world's populations.
显然 早期现代人的迁徙部落
So, clearly, the wandering tribes of early modern humans
与人类近亲发生了亲密接触
readily mixed with our human cousins.
在他们开始接触的地方
Where they come into contact,
他们产生了交集 留下了后代
they are doing some interbreeding where they overlap.
可能包括收养小孩
And it could have included things like adopting babies,
寻找尼安德特人的孤儿和丹尼索瓦人的宝宝
finding orphaned Neanderthals, Denisovan babies,
把他们带到部落里带大
taking them into the group and then bringing them up in your group.
这可能是留下后代的原因
So that could have been part of it, too.
有时也可能是掠夺其他群落
At other times, it might have been raiding groups
抢夺女人 因为本群落缺乏女性
and stealing women, because a group lacked females.
实际上他们可能会去偷一些回来
They would actually go and steal some.
这些在今天的黑猩猩种群里也有出现
And this happens today in chimpanzee groups
在现代的狩猎-采集者聚群中也有发生
and it happens today in some hunter-gatherer groups,
因此我肯定过去也是这样
so I'm sure that was happening as well.
我认为这种联姻的形成原因
So I think we've got a whole range of possibilities
多种多样
of how these matings actually happened.
我们认识到 这些人类群体
We have realised that these groups of humans
并没有完全灭绝
are not totally extinct, if you like.
有一小部分今天仍存留在现代人体内
They live on a little bit in people today.
人类失落的历史中
The most fascinating and surprising secrets
最迷人也最令人惊喜的秘密终于被揭开了
of our long-lost past are finally being uncovered.
从前认为是晚期智人征服了其他人种
The idea of modern humans crushing all other species
简单又戏剧化地占领了地球
in a brief and dramatic conquest of the globe
现在各人类种群逐渐同化的观点占据了主导
has to give way to a process of assimilation
同化使人类演变成今天的样子
that has truly shaped who we are today.
但故事还没有结束
But that's not the end of the story.
随着基因技术的进步
As genetic techniques get better
我们对DNA的探究加深
and as we delve deeper into our DNA,
最近一个新的秘密被揭开
a new secret has recently been revealed.
在当今的非洲大草原上
On the grasslands of present-day Africa,
某些人的基因组里深藏着的基因
hidden deep in the genomes of certain people,
来自第五个消失的人类族群
are the remnants of a fifth human population,
这一失落群落的其他踪迹已消失殆尽
a lost tribe of whom all other traces have disappeared.
非洲中部平原的环境严峻又残酷
The plains of central Africa are a harsh and unforgiving environment.
一个与世隔绝的原始人部落仍顽强生存
And yet, an isolated hominid tribe doggedly clings to survival,
未在这片大地留下一丝痕迹
leaving no trace in the landscape.
这个部落其实是在一万五千千米外
This tribe was actually discovered 9,000 miles away in Seattle,
美国西海岸的西雅图发现的
on the West Coast of America.
遗传学家乔舒亚·阿基一直致力于分♥析♥
Geneticist Joshua Akey has been analysing the genes
某些现代非洲人的基因
of certain modern African populations
发现了在现代其他人种身上
and he's uncovered sections of DNA
找不到的DNA序列
that can't be found in other modern humans.
我们能够鉴定出
We were able to identify sequences
起源古老的基因序列
that we're confident are archaic in origin,
但当我们试着将序列与尼安德特人
but when we try to match them to the Neanderthal
或是丹尼索瓦人的序列匹配时
or the Denisovan genomes,
结果却完全不匹配
they didn't match at all.
显然 该基因来自于
So this is clearly
生存在非洲的不知名人类群落
from an unknown group of humans that existed in Africa.
乔舒亚·阿基教授 华盛顿大学
我们没有他们的化石数据
We don't have any fossil data for them,
对他们一无所知
we don't know anything about them,
只有当今非洲人身上保留的
except for the trace amount of DNA
他们的微量DNA
that they've left in the present-day individuals from Africa.
想想人类系谱图
So, think about the human family tree.