DNA Tests Can’t Tell You Your RaceDNA检测无法验明种族

It’s always a mess when Latinx1 folks take DNA tests. Things go alright， until we get to the “ancestry2” portion， which some commercial genetic tests label as “ethnicity.”

拉美裔做DNA检测总是一片混乱。本来一切正常，可一旦涉及“血统”部分（一些商业性基因检测称之为“种族渊源”）就会乱套。

My grandfather is Mexican， but fair3-haired and blue-eyed （we sometimes call people who look like him bolillo， which means “white bread”）. When he got his report back from Family-TreeDNA， he found out he had more North American ancestry than expected. My friend’s brother， also Mexican， came into the living room with his tests results printed out. “I found I’m 3 percent black，” he said.

我祖父是墨西哥人，但金发碧眼（我们有时称他这类长相的人为bolillo，意为“白面包”）。他收到家庭树基因检测公司的检测报告后，发现自己的北美血统成分高于预期。我朋友的兄弟也是墨西哥人，他拿着打印的检测结果走进客厅说：“我发现自己有3%的黑人血统。”

In the past few years at-home genetic testing has grown into a billion-dollar industry; since 2013， more than 26 million people have sent in their DNA for analysis. And while companies like 23&Me， AncestryDNA， and MyHeritage claim to be able to tell your “ethnicity”—a word they know many people will read as a synonym for “race”—none of them explicitly offer to tell consumers their racial make-up. There’s one simple reason for that： The science just doesn’t exist.

在过去几年里，居家基因检测已发展成为一个规模达10亿美元的产业；自2013年以来，已有2600多万人将自己的DNA送去检测。虽然诸如我与23对染色体公司、家谱基因检测公司和MyHeritage之类的公司声称能验明人的“种族渊源”——他们知道很多人会把这个词解读为“种族”的同义词——但它们当中没有任何一家公司明确表示可告知消费者其种族成分。原因很简单：这种科学知识根本不存在。

To understand this， let’s go back to my friend’s brother. He thought the test told him he was “3 percent black，” when in fact it reported that he had a 3 percent chance of having genetic ancestry from some part of the African continent.

为了理解这一点，我们再回到刚才我朋友的兄弟的例子。他以为检测结果显示他有“3%的黑人血统”，但其实检测报告说的是他的祖先来自非洲大陆某地的概率是3%。

How’s that different than being “3 percent black”？ First off， that percentage is being interpreted incorrectly. A lot of people read their DNA tests like a pie chart： You’re 25 percent this or 50 percent that. But that’s not at all what the statistics represent.

这与“3%的黑人血统”有何不同？首先，对该百分比的解读有误。很多人将自己的DNA检测结果解读为一张饼图：你有25%的这个或50%的那个。但那根本不是该统计数据所表示的意义。

“They are fractions， estimates. It’s saying that your genome has a certain percent estimate of representing a certain area，” says Marcus Feldman， a professor of biological sciences at Stanford University and director of the Morrison Institute for Population and Resource Studies.

“它们是分数，是估值，表示你的基因组按估算有一定比率代表某个地区。”斯坦福大学生物学教授、莫里森人口与资源研究所所长马库斯·费尔德曼说。

Feldman explains that when it comes to people’s roots， the tests are saying something more like： We’re 30 percent confident that your DNA indicates ancestry from Okinawa， Japan. That’s not the same thing as saying someone is 30 percent Okinawan.

费尔德曼解释说，就寻根问祖而言，此类检测结果更像是在说：我们有30%的把握相信，你的DNA表明你的祖先来自日本冲绳。这不等于说某人有30%的冲绳血统。

The vast majority of human DNA—we’re talking 99.9 percent—is entirely identical between individuals. So when the code diverges between two people， that’s interesting to scientists. A DNA ancestry test scans the entirety of your genome looking for single-letter differences. Statistical experts like Feldman have figured out that people from the same continent， on average， tend to have certain variations in the same regions of DNA. Still， it’s impossible to say that one tiny nuance comes from a specific place; analysts can only note when someone’s differences overlap a lot with a general geographic group.

绝大多数的人类DNA——我们说的是99.9%——在个体之间是完全相同的。因此，当两人之间的DNA密码有差异时，就会引起科研人员的关注。DNA血统检测筛查你的整个基因组，搜寻单字母差异。费尔德曼等统计专家发现，一般来说，来自同一大洲的人往往在相同的DNA区域有特定变异。但尚无法断言某一细微变异来自具体哪个地方；只有当某人的变异与某一地域整个群体有很多共同之处时，分析人员才会关注。

“You can’t take your DNA and chop it up and say， ‘This bit came from here， and that bit came from there，’” Feldman says， laughing.

费尔德曼笑言：“你不能把自己的DNA剁碎，然后说‘这一小块来自这里，那一小块来自那里’。”

You might think your ancestry works sort of like inheriting genes from your parents—an even 50/50 split. But that’s not the case when you go back another generation， as DNA reshuffles4 and reorganizes with every new transfer. So even if your mom gave you 50 percent of her own genes， doesn’t mean you got an even portion of， say， her Pakistani parent’s. In fact， if you dig far enough， it’s possible you’ll find a direct ancestor that you have no genes in common with.

你或许认为自己的血统有点像继承父母的基因，是对半开。但再上溯一代则不然。因为每次新的传承都会发生DNA重排、重组。因此，即使你妈妈将她50%的自身基因传给你，也不意味着你等比均分到（比如说）她的巴基斯坦父亲或母亲的基因。事实上，如果挖掘得足够深远，你可能会查找到一个与你之间毫无共同基因的直系祖先。

This means that you and your sibling can have significantly different ancestry results， given you’ve each inherited different portions of your parents’ DNA （unless you’re identical twins）.

这意味着你与兄弟姐妹之间在血统检测结果上可能会有明显差异，因为你们各自继承了不同比例的父母DNA（除非你们是同卵双胞胎）。

That brings us to another important detail： the fact that ancestry and physical appearance （or phenotypic5 traits） don’t directly overlap. Characteristics like skin color， hair texture， and eye shape are controlled by thousands of different genes—separate from the ones scientists look at when composing an ancestry profile. As a result， someone with a high estimate of West African ancestry might not look or even identify as black. Similarly， an individual whose tests come back with a very low estimate of West African ancestry might actually be black.