我们之间有血缘关系吗

这个是你
This is you.
这些是你的亲属 他们的关系网组成了一个
And these are your ancestors, a huge pyramid stretching into the past
平衡的金字塔
and balancing right on your head.
那么你究竟有多少亲属呢
How many ancestors do you have?
首先 你有两位父母
Well, you have two parents.
四位爷爷奶奶 和八位祖父母
Four grandparents and eight great-grandparents.
假如能四代同堂的话 你的直系先辈能达到30人
Four generations back, your direct ancestors total 30.
如果我们按照这种方式计算 每一代人的数量相当于后一代的两倍
If we continue down this line, doubling every step,
计算到40代人的时候 先辈的数量就达到了大概一万亿
just 40 generations ago we’d find a trillion ancestors,
假如他们和你都生活在一个年代
all living *at the same time*.
这简直不可想象
Which is… ridiculous.
这个数量不仅多过现存的人类数量
That’s not only more people than have ever been alive,
甚至超越银河系的星球量
it’s more stars than are in the Milky Way.
自从20万年前人类出现以来
Since our species came on the scene 200,000 years ago,
你的前面已经历经了七八千代
there’ve been maybe 7 or 8 *thousand* generations of humans leading up to… you.
那么你的先辈们都去哪里了呢
So where are all your missing ancestors?
显而易见 近亲繁殖是绝对存在的
Clearly, there’s been some inbreeding.
【音乐】
[MUSIC]
当然 我们并不是在开玩笑 也不是在说西班牙皇室 更不是在讨论瑟曦和詹姆的关系
We’re not talking banjo-playing, King-of-Spain, Cersei-Jamie inbreeding,
注释：瑟曦·兰尼斯特和詹姆·兰尼斯特是《权利的游戏》中的角色
两人是亲兄妹 却发生了亲密的关系
但是 家族树不可避免会长出分叉
but every family tree inevitably grows forks.
在探探出现之前 伴侣的选择往往局限于你的活动范围
Before Tinder, choices for mates were often limited to as far as you could walk.
注释：探探是国外的一款手♥机♥交友APP
作用是基于用户的地理位置，每天“推荐”一定距离内的四个对象
甚至查尔斯·达尔文和阿尔伯特·爱因斯坦这样的人都娶了自己的表亲
Even people like Charles Darwin and Albert Einstein married their first cousins.
因为很多拥有共同祖先的人都生育了后代
Because so many people with shared ancestors have reproduced,
而我们的祖先的实际数量比数学计算的要少得多
our number of actual ancestors is much smaller than what simple math tells us.
如果用花哨的数学来计算 考虑到人们的迁徙、生活、配对、
If we replace that with fancy math, factoring in how people moved and lived and paired up…
寿命、交易、地理等等因素 比如成吉思汗 我们发现了一个有趣的现象
life expectancy, trade, geography, Genghis Khan… we find something interesting:
注释：成吉思汗是冷兵器时代闪电战的英雄 被称为“世界的征服者”
他的蒙古骑兵让欧洲的基♥督♥教世界、西亚的伊♥斯♥兰♥教世界心惊胆寒
现存的人类当中 家族成员几乎彼此都拥有一位共同的祖先
every human alive today shares a common ancestor in their family tree,
而这位祖先最早追溯到3000年前
and this person lived only around 3,000 years ago.
所以说 下次你在网上和陌生人起争执时
That’s right, next time you get in a fight with a stranger on the internet,
要记得你们拥有一个曾曾曾……
just remember that you share the same great great great great great
（快进）曾祖父母
(fast foward) great grandfather or grandmother.
当然 我们并不认识这位祖先
But we don’t know who that person was.
只是通过数学计算得知他们的可能存在 他们也没有留下什么化石、古董文物、
The math tells us they must have existed, but they didn’t leave fossils or artifacts.
文书之类的给我们考证
Or like, a note or something.
再说了 给74亿曾曾曾……曾孙们写生日卡片
Though, writing birthday cards for each of their 7.4 Billion great great great great great
也是一个令人暖心的举动
(fast forward) great grandchildren would have been nice gesture.
我们的身体都刻录有祖先的基因信息
But we all carry a record of our ancestors in our genes.
因为DNA总是重复不断地复♥制♥给下一代 哪怕出现一点小插曲也会复♥制♥下去
Because DNA is copied over and over, every so often a mistake is written in.
然而 当你复♥制♥复印版时 得到的依然像原版吗
You know how when you make a copy of a copy, it’s doesn't come out as sharp?
比如说 我们体内的大部分DNA会发生变异而不影响机体运作
Like that, but since most of our DNA can be changed without affecting how things work,
而这些变异会遗传给下一代
many of these mutations slip through to the next generation.
这些基因变异会随着时间的推移以恒定的速率积累
These genetic changes accumulate at a steady rate through time,
因此 科学家们可以像分子钟那样读取它们 并且估算历经的时间
so scientists can read them like a molecular clock, and estimate how much time has passed.
注释：分子钟在1962年由扎克坎德尔和鲍林提出 即分子水平的进化存在恒速现象
个体内部的基因变异量可以告诉我们这些个体在血缘关系上的亲疏远近
And which changes individuals share tell us how closely or distantly related they are.
不同的个体看起来的确不一样 但是在DNA层面上是非常相似的
Human "seemed "really different, but on a DNA level were remarkably similar.
在中非 黑猩猩成群结队生活在一起
Groups of chimps in Central Africa, living right next to each other,
基因变异量比我们在人类群体中发现的还多
show more genetic variation than we find in the entire human population.
这种基因相似性表明现代人类在世间万物中是新物种
This genetic similarity tells us that our species is new,
从某点来说 我们的人口曾经很少
in the big scheme of things,and that at one point our population was small,
也许只有一万人
maybe as few as 10,000 of us.
换句话说
To put that in perspective,
这只是布鲁斯·斯普林斯汀平均观众量的三分之一
that’s only a third of your average Bruce Springsteen crowd.
布鲁斯·斯普林斯汀 1949.9.23日出生于美国 摇滚歌♥手 作词作曲家
对不起啦 老板
Sorry Boss.
今天 任何两个人每1000对碱基对中只有一对不同
Today, any two humans only differ by about 1 out of 1000 DNA base pairs.
但是我们的基因组太大了 大到有成千上万个不同的核苷酸
But our genome is so big, that’s still millions of single letter differences,
或者说单核苷酸多态性
or SNPs, for “single nucleotide polymorphism”.
我们大多是比对这些变异的数据 即单核苷酸多态性群
We tend to see combinations of these changes, chunks of SNPs,
查看基因的来源地
associated with different geographic locations.
基因检测公♥司♥
Companies that test your DNA ancestry
会读取基因组中变异的单核苷酸
read thousands of these single letter changes in your genome,
然后标记出独属于你的基因变异
to make a sort of signature of your unique genetic variation.
他们会拿你的数据
Then they compare your signature to thousands of reference individuals
同上千份来自世界各地的基因进行对比
from various parts of the world,
然后用大量华丽的数据来推算出
and do a bunch of fancy math to see which parts of your genome
来自某个地方的最有可能是基因组的哪部分基因
most likely came from certain geographic areas.
我的基因结果差不多是这样
My genetic results: Pretty much look like this.
我父母的祖先来自北欧和斯堪的纳维亚半岛
My ancestors on both sides of my family, are from Northern Europe and Scandinavia,
这也正好解释了我为啥姓这个性 这么高 还晒不黑
which explains my last name, why I’m tall, why I don’t tan,
以及比三分之二的人类拥有更多的尼安德特人的DNA
and also why I carry more Neanderthal DNA than 2/3rds of people.
注释：尼安德特人 简称“尼人” 是现代欧洲人祖先的近亲 但在两万四千年前消失了
如果你好奇我怎么会有尼人DNA
If you are confused why I have Neanderthal DNA?
你可以回看我之前的视频
You should watch our last video.
我的基因检测并没有什么特别之处
I didn’t find any surprises,
但是很多人都发现了原先并不知道的血缘关系
but many people learn about ancestry they didn’t know they had.
我们的身世来源不一定能从外表上看出来 但是DNA就不一样了
Where we come from isn’t always obvious on the outside, but DNA doesn’t lie.
在此之前 我们通过数学计算得知一位
Before, using math, we identified an ancestor,
与我们时代非常接近并且和我们大家都相关的祖先
not too long ago, that’s related to all of us.
但是这个人的基因序列在遗传过程中已经被严重破坏
But that person’s genetic influence has been shuffled
以至于无法从我们如今的DNA中看出原型
so much it’s invisible in our DNA today.
至今为止有谁的基因在遗传过程中没有破坏过吗
Is there someone whose genes have been passed on, unbroken, to today?
有没有人完整遗传到了现代人的始祖母的指纹
Some leftover fingerprint from the mother of everyone alive?
当然有
There is.
人体内有47条染色体
You have a 47th chromosome.
第47条染色体♥位♥于细胞的能量工厂——线粒体
It lives in mitochondria, the POWERHOUSE OF THE CELL!
对的 我们又要开始分♥析♥了
OK so we’re doing that again！
线粒体可以自♥由♥移♥动♥
mitochondria used to be free-swimming.
它们有自己的遗传物质
They have their own genetic material.
第47条染色体不像其它46条 在遗传过程中不会被破坏序列
Unlike your other 46 chromosomes, there’s no shuffling when it’s passed between generations.
更重要的是 你体内的线粒体全部来自母亲的卵子
What’s more, all your mitochondria came from your mother’s egg,
而不是父亲的精♥子♥
not your father’s sperm.
它们可以通过家族女性成员
They trace an unbroken line of ancestors
追踪一条完整的祖先的基因序列
stretching back through every female in your family tree.
通过比对数千年来基因的异变数据
By comparing the changes that have accumulated over the millennia,
我们发现 最古老的人体线粒体DNA来自非洲
we find the most ancient human mitochondrial DNA comes from Africa,
非洲是人类起源的地方
where our species originated.
我们甚至可以追溯到15万年前的一位女性
We can even trace it back to one woman, about 150,000 years ago.
与她同行的还有其她女性智人 但是只有她这一脉存活至今
Other Homo sapiens females lived alongside her, but only her lineage lives on today,
其她的都灭绝了
all other Homo sapiens lineages are extinct.
她堪称线粒体版的“夏娃”
This is mitochondrial Eve.
注释：夏娃是《圣经》中的人物 根据记载
她是神从亚当身上取下的一根肋骨而创造的女人 是众生之母
我们每一个人都是她的后代
And every single one of us, descend from her.
从最真实的意义上说 我们就是一家人
In the truest sense, we really are family.
哪怕我们只是隔了上百辈的表兄妹什么的
Even if we’re just hundredth cousins or something.
我们的血缘关系不仅仅联♥系♥了过去
But our ancestry isn’t just branches stretching into the past,
还延伸到未来
it’s also a tree that extends into the future.
如今 我们将比以往任何时候都拥有更多的力量
today，we have more power to mold that future
来塑造未来
down to the genetic level, than we’ve ever had before.
那么 人类的未来会是什么样子呢
So what might our species’ future look like?
请听下回分解
Next time.
保持好奇心
Stay curious.
这段视频属于人类故事的特别系列
This video is part of a special series we’re doing about the story of our species:
——人类的起源、人类的联♥系♥以及人类的未来
Where we came from, how we’re all connected, and where we’re going.
如果你还没有看过第一部分和第二部分 还不了解家族先辈的化石
If you haven’t already, check out part 1 and 2 to trace the fossils in our family tree
也不知道为什么我们是唯一现存的人类
and learn why we’re the only humans left.
记得点击关注 精彩内容不容错过
And be sure to subscribe so you don’t miss any of our videos.