韩冬:为什么男人无名指比中指长

Why Most Men's Ring Fingers Are So Long

为什么男人无名指比中指长

Finger length linked to aggression, musical ability, sexual orientation.

手指的长度与人的暴力程度、音乐天赋和性取向息息相关。

Is your ring finger longer or shorter than your index finger? The reason for the difference is in our hormones, a new study in mice shows for the first time.

Before birth, the sex hormones estrogen and testosterone control genes that in turn dictate finger length, the study found. Like us, mice naturally have both hormones in their bodies. (Get a genetics overview.)

你的无名指比中指长还是短？一项新的小鼠研究实验首次表明，这种差异与我们的荷尔蒙有很大关系。

该研究表明，在我们出生之前，体内的雌激素和雄激素这两种性激素通过基因决定了我们的手指长度。和人类一样，老鼠生来体内也同时存在这两种激素。

As a result, most men have ring fingers that are longer than their index fingers, and the reverse is true in women.

所以，男性大多都是无名指长于中指，而女性则相反。

Differences in finger length have been repeatedly linked to a range of human traits, from aggression to musical ability to sexual orientation. There are also connections to health problems such as autism, depression, heart attacks, and cancer.

指长差异与各种人类特征息息相关，从攻击性到音乐天赋，再到性取向。手指长度通常和一些病症也有很大关系，比如自闭症，抑郁症，心脏病和癌症。

(See "Women With High Testosterone Take Financial Risks.")

（点此阅读“雌激素水平较高的女性易陷入金融危机”）

"It's difficult to look at an adult or a newborn child and determine what was happening during their embryonic development," said study leader Zhengui Zheng, a developmental biologist at the Howard Hughes Medical Institute in Florida.

该研究组的组长郑珍贵是弗洛里达州哈弗大学休斯敦医学院的一名发育生物学家。他说：“单看一个成年人或一个刚出生的小宝宝很难看出他们在子宫里成长期间经历了什么。”

"But the discovery that digit proportions reflect the prenatal hormonal environment helps us to explain all those correlational studies," said Zheng, who works in the laboratory of study co-author Martin Cohn.

郑说：“但是我们发现手指能够反映出产前的激素环境，这为我们做此类相关研究提供了很大的帮助。”郑珍贵在该研究的合伙人马丁·科恩的实验室内工作。

First Proof That Hormones Affect Finger Length

Scientists had already suspected that sex hormones played a part in finger length, but "causality had never been demonstrated—no one had ever tested the hypothesis that these hormones directly cause the digits to grow differently in males and females," Cohn said.

第一大证据：荷尔蒙影响手指长度

科学家们早就开始怀疑性激素对手指长度有一定影响，但据科恩说“此中缘由却从未有人证实过——没有人曾证实这一假设，即性激素会直接导致男女手指长度差异。”

Zheng and Cohn took two general approaches for their experiments, which are detailed this week in the journal Proceedings of the National Academy of Sciences.

郑珍贵和科恩在他们的实验中采用了两种普通的方法，这在本周的《国家科学院院刊》上有详细内容。

First, they used genetic tools to deactivate cell receptors—molecules that send and receive signals to and from other cells—for testosterone and estrogen in the developing limb buds of mouse embryos. Second, the scientists boosted the hormone levels of pregnant female mice.

首先，他们用基因手段禁止了细胞受体的活动——细胞受体即那些向其他细胞发送和从其他细胞接受信号的分子们——因为雌激素和雄激素存在于正在发育的老鼠胚胎的肢芽中。然后，科学家给怀孕的母老鼠注入激素。

The results proved consistent: Male mice that lacked testosterone receptors in the womb were born with shorter, typically feminine digit proportions, or had index digits longer than their ring digits. Male mice without estrogen receptors had longer ring digits.

实验结果与人类一致：在子宫里就缺少雄激素受体的雄性老鼠出生后指爪部分会短些，雌性老鼠指爪部分尤其短，或者它们的中指比无名指长。而没有雌激素受体的雄性老鼠的无名指则更长。

Female mice that lacked an estrogen receptor were born with longer digits, and those that did not have testosterone had shorter, superfeminine digits.

而缺少雌激素受体的雌性老鼠生来指爪就更长，那些没有雄激素老鼠的指爪则更短，并且非常女性化。

The team also found that hormones controlled the rate of cell division in a mouse's developing digits.

研究组还发现，激素还决定着老鼠正在发育的指爪中细胞的分裂率。

In the ring digit, testosterone stimulates cell division, building up cartilage and bone to make the digit longer. Estrogen, on the other hand, slows down cell division, leading to a shorter digit.

无名指中的雄激素会刺激细胞分裂，生长出软骨和骨骼使该指变得更长。而另一方面，雌激素会减缓细胞分裂，使手指变短。

But what really surprised the researchers was that it wasn't the absolute level of hormones—say, the total amount of estrogen—that influenced digit length, but rather the balance of hormonal activity in the mouse's limb buds, Cohn noted.

科恩说，但实际上真正让研究人员惊讶的是，影响手指长度的不是激素的绝对水平——比如说雌激素的总量——而是老鼠肢芽中激素活力的平衡状态。

Mouse-Digit Experiment "Elegant"

老鼠指爪实验“非常优美”

Scott Simpson, an anatomist at Case Western Reserve University in Ohio, said the study used a "very elegant and well-designed experiment."

斯科特·辛普森是俄亥俄州凯斯西储大学的一位解剖学家。他评价该研究用了一个“非常优美而构思精致的实验。”

That's because the team traced every step in how hormones change mouse bodies, from the gene level to maturity—a still little-understood progression, said Simpson, who was not involved in the research.

那是因为该研究组描出了老鼠体内激素的每一次变化，从基因状态到成熟期——这个发展历程至今仍保持着神秘，辛普森说。他并不是该研究组的一员。

(Explore a human-body interactive.)

"We all know we are the product of our genes, what are all the steps from gene to us?"

“我们都知道基因决定了每个个体，但基因是如何使我们成为现在的我们的呢？”

What's more, the study is valuable in finding that hormones begin affecting us much earlier than thought—as early as the first trimester of pregnancy. Many scientists have believed that hormones are more active after birth.

而且，该研究还有另一个价值，那就是我们发现激素开始影响我们比我们预想的早多了——早到怀孕期的前三个月。许多科学家一直认为激素在我们出生后才更加活跃。

"This isn't just an interesting curiosity that's focused on the hand—it really says something about the behavioral and development biology of adults," he noted.

他补充道：“这可不仅仅只是关于手指的有趣发现——它对于成年人的行为发育生物学有着极大意义。”

Finger Length a Snapshot From the Womb?

手指长度是来自子宫的快照？

Overall, the results suggest that our finger length can be almost a "readout" of a person's hormonal balance during a very narrow window of development in the womb, Cohn said.

科恩说，总之，这个结果表示，通过子宫发育这个小窗口，我们几乎能从手指长度“读出”一个人的激素状况。

For instance, if a man has a longer index finger than ring finger, he may have had an elevated dose of estrogen at some point during his development—which is not necessarily a bad thing.

比如说，如果一个男性的中指长于无名指，那么某种程度上他在发育期雌激素水平较高——这不一定是件坏事。

But, in some cases, such irregularities can lead to medical conditions in adulthood. Exposure in the womb to synthetic chemicals that mimic or block hormones, for example, has been linked to health problems in children and adults.

然而，对一部分人来说，这种反常情况可能导致成年时健康出问题。在子宫内就接触人造化学物质——比如说，它们会模拟或堵塞激素，这会使孩子在儿童期和成年期出现健康问题。

(Also see "Sex-Changing Chemicals Can Wipe Out Fish, Study Shows.")

Previously, it was difficult to know if a mother had been exposed to a chemical during pregnancy that disrupted hormone activity in her child.

但在此之前，谁也不知道一位准妈妈在怀孕时是不是接触了那些会扰乱胎儿激素活动的化学物质。

Now, "our findings suggest such an event might leave a signature," Cohn said. That "might be a useful tool" for figuring out the cause of a disease, malformation, or even a behavioral trait.

目前，科恩说道：“我们发现此类事件是可能留下痕迹的。”那“可能是找出疾病病因、畸形或某种行为特征的有效手段”。