VOA科学技术2024--Study Aims to Find Out Why Some People Are Left-handed

What do Lady Gaga, Barack Obama, and Bill Gates have in common - aside from their fame? They are all left-handed.

But why are 10 percent of people left-handed while most are right-handed?

Researchers are trying to find out.

A recent study identified a genetic² cause of left-handedness in some people. Researchers found rare variants⁴ of a gene¹ involved in controlling the shape of cells. They found the variants to be 2.7 times more common in left-handed people.

These genetic variants account for possibly 0.1 percent of left-handedness. But the researchers said a gene, called TUBB4B, might play a part in the development of brain asymmetry⁵.

In most people, the two halves, or hemispheres, of the brain have slightly different structures and are dominant⁶ for different activities.

"For example, most people have left-hemisphere dominance for language, and right-hemisphere dominance for tasks that require directing visual attention to a location in space," said Clyde Francks of the Max Planck Institute for Psycholinguistics in the Netherlands. Francks was the top writer of the study published recently in Nature Communications.

Francks suggested that for most people, the left side of the brain controls the dominant right hand. "The nerve fibers⁸ cross from left-to-right in the lower part of the brain," Francks said. He added, "In left-handers, the right hemisphere is in control of the dominant hand. The question is: what causes the asymmetry of the brain to develop differently in left-handers?"

TUBB4B controls a protein that gets formed into filaments¹⁰ called microtubules. These microtubules give structure to the insides of cells. The changes in TUBB4B that are more common in left-handers suggest that microtubules are involved in setting up the brain's normal asymmetries¹¹, Francks said.

The two brain hemispheres start to develop differently in the human embryo¹². Scientists do not know the mechanism¹³ that controls this.

"Rare genetic variants in just a handful of people can pinpoint¹⁴ genes¹⁵ that give clues to developmental mechanisms¹⁶ of brain asymmetry in everyone," Francks added. TUBB4B is an example.

The study's findings were based on genetic data from more than 350,000 middle-aged¹⁷ to older adults in Britain. It was from the UK Biobank. About 11 percent of the people involved were left-handed.

For most people, left- or right-handedness might come down to chance. Changes in the levels of some molecules¹⁸ during important times of brain development could influence it, Francks suggested.

Historically, many cultures disapproved¹⁹ of left-handedness and forced people to become right-handed.

In English, the word "right" also means "correct" or "proper." And the expression a "left-handed compliment" means that a comment might seem nice but is an insult.

The levels of left-handedness differ around the world, with lower rates in Africa, Asia and the Middle East compared to Europe and North America, Francks said.

"This likely reflects suppression of left-handedness in some cultures - making left-handed kids switch to right-handedness, which also used to happen in Europe and North America," Francks added.

The new findings might have use in the field of mental health. People with schizophrenia are around twice as likely to be left-handed or ambidextrous²⁰. People with autism are around three times as likely, Francks said.

He observed that genes involved in developing the brain in early life might be involved in brain asymmetry and mental health.

"Our study found suggestive evidence of this, and we have also seen it in previous studies where we looked at more common genetic variants in the population," Francks added.

Words in This Story

variant³ - n. different in some way from others of the same kind

asymmetry - n. having two sides or halves that are not the same

dominant -adj. having the most control, strength or ability to influence

fiber⁷ -n. a long, thin piece of material that has strength to it

filament⁹ - n. a long thread made of proteins

mechanism - n. a process or system produces a particular result

ambidextrous - adj. able to use both hands equally well

1 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

2 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

3 variant   

adj.不同的，变异的；n.变体，异体

参考例句：

• We give professional suggestions according to variant tanning stages for each customer.我们针对每位顾客不同的日晒阶段，提供强度适合的晒黑建议。
• In a variant of this approach,the tests are data- driven.这个方法的一个变种，是数据驱动的测试。

4 variants   

n.变体( variant的名词复数 )；变种；变型；（词等的）变体

参考例句：

• Those variants will be preserved in the'struggle for existence". 这些变异将在“生存竞争”中被保留下来。 来自辞典例句
• Like organisms, viruses have variants, generally called strains. 与其他生物一样，病毒也有变种，一般称之为株系。 来自辞典例句

5 asymmetry   

n.不对称；adj.不对称的，不对等的

参考例句：

• These bands must introduce longitudinal asymmetry in the planetary albedo.这些云带必定引起行星反照率的经向不对称性。
• In any event the asymmetry is clear enough.总之，不对称是非常明显的。

6 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。

7 fiber   

n.纤维，纤维质

参考例句：

• The basic structural unit of yarn is the fiber.纤维是纱的基本结构单元。
• The material must be free of fiber clumps.这种材料必须无纤维块。

8 fibers   

光纤( fiber的名词复数 )； （织物的）质地； 纤维，纤维物质

参考例句：

• Thesolution of collagen-PVA was wet spined with the sodium sulfate as coagulant and collagen-PVA composite fibers were prepared. 在此基础上，以硫酸钠为凝固剂，对胶原-PVA共混溶液进行湿法纺丝，制备了胶原-PVA复合纤维。
• Sympathetic fibers are distributed to all regions of the heart. 交感神经纤维分布于心脏的所有部分。

9 filament   

n.细丝；长丝；灯丝

参考例句：

• The source of electrons in an electron microscope is a heated filament.电子显微镜中的电子源，是一加热的灯丝。
• The lack of air in the bulb prevents the filament from burning up.灯泡内缺乏空气就使灯丝不致烧掉。

10 filaments   

n.（电灯泡的）灯丝( filament的名词复数 )；丝极；细丝；丝状物

参考例句：

• Instead, sarcomere shortening occurs when the thin filaments'slide\" by the thick filaments. 此外，肌节的缩短发生于细肌丝沿粗肌丝“滑行”之际。 来自辞典例句
• Wetting-force data on filaments of any diameter and shape can easily obtained. 各种直径和形状的长丝的润湿力数据是易于测量的。 来自辞典例句

11 asymmetries   

n.不对称( asymmetry的名词复数 )

参考例句：

• However the pattern of asymmetries is different for the pre-and post-QFII periods. 然而，格局的不对称性是不同的为会前和会后QFII时期。 来自互联网
• One problem, of course, is the striking asymmetries between the group's members. 其中一个问题，当然是集团成员之间惊人的不对称。 来自互联网

12 embryo   

n.胚胎，萌芽的事物

参考例句：

• They are engaging in an embryo research.他们正在进行一项胚胎研究。
• The project was barely in embryo.该计划只是个雏形。

13 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

14 pinpoint   

vt.准确地确定；用针标出…的精确位置

参考例句：

• It is difficult to pinpoint when water problems of the modern age began.很难准确地指出，现代用水的问题是什么时候出现的。
• I could pinpoint his precise location on a map.我能在地图上指明他的准确位置。

15 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

16 mechanisms   

n.机械( mechanism的名词复数 )；机械装置；[生物学] 机制；机械作用

参考例句：

• The research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
• He explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》

17 middle-aged   

adj.中年的

参考例句：

• I noticed two middle-aged passengers.我注意到两个中年乘客。
• The new skin balm was welcome by middle-aged women.这种新护肤香膏受到了中年妇女的欢迎。

18 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

19 disapproved   

v.不赞成( disapprove的过去式和过去分词 )

参考例句：

• My parents disapproved of my marriage. 我父母不赞成我的婚事。 来自《简明英汉词典》
• She disapproved of her son's indiscriminate television viewing. 她不赞成儿子不加选择地收看电视。 来自《简明英汉词典》

20 ambidextrous   

adj.双手很灵巧的，熟练的，两面派的

参考例句：

• I'm neither left-handed nor right-handed;I'm ambidextrous.我不是只用左手或右手，我是双手并用。
• Jack is an ambidextrous hitter;he can bat right-handed or left-handed.杰克是一位双手都很灵巧的打击手，他可以用右手或左手打击。