Why are there lefties and righties?

2024/11/13

Unexplainable

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Bird Pinkerton

Meredith Hodnot

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Jonquilyn Hill: 作为一名经常混淆左右手的个人，我对这一话题非常感兴趣，并希望了解其背后的科学原因。我与其他嘉宾讨论了三个相关的科学谜题：为什么有些人难以区分左右手？为什么存在左撇子？为什么生命分子只存在单一手性？ Bird Pinkerton: 研究表明，区分左右手的难易程度因人而异，这可能是因为人体左右对称，导致区分难度增加。虽然研究发现人们在区分左右手时会参考自身身体，但这并不能解释为什么有些人能自动区分，而有些人却不能。关于左撇子的成因，研究表明遗传因素约占25%，但主要原因可能是随机的，这与细胞内部的随机活动有关。 Meredith Hodnot: 分子手性在化学反应中至关重要，药物沙利度胺的例子说明了这一点。生命分子只存在单一手性形式，这是一个困扰科学界150多年的谜题。最近的研究表明，早期地球上的磁性矿物可能对生命分子的手性选择起到了关键作用，磁场可能分离了左旋和右旋分子，导致生命分子只存在单一手性。 Ineke van der Ham: 区分左右手并非异常现象，而是自然现象，这与人体左右对称有关。 Veronica Odinsova: 左右手习惯的遗传因素约占25%，主要原因可能是随机的。 Furkan Ozturk: 分子具有手性，即存在镜像异构体，在化学反应中，其手性可能至关重要。实验表明，磁性矿物可以分离左旋和右旋分子，这可能是早期地球上生命分子单一手性的原因之一。

Deep Dive

Key Insights

Why do some people struggle to tell their left from their right?

It's a natural phenomenon due to our symmetrical nature. When a stick figure is facing away, it's easier to distinguish left and right, suggesting we consult our own bodies to figure it out. The exact reason why some do this automatically and others don't is still unclear.

What makes someone a lefty or a righty?

Genetics play a role, but only about 25%. Scientists think it's largely random due to 'jitter in the system,' where cellular activity in the womb leads to handedness. There are 41 gene locations influencing this, but the exact mechanism remains unexplained.

Why do molecules of life only exist as either left or right-handed?

Recent research suggests magnetic minerals on early Earth could have separated left and right-handed molecules, favoring one over the other. This could explain why life molecules are homochiral, though the origins of life itself remain unsolved.

Chapters

This chapter explores the mystery of why some people find it difficult to distinguish between their left and right sides, a phenomenon that affects people like Piper and the host, JQ.

People consult their own bodies to figure out left and right.
When a stick figure is turned away, it's easier to tell left and right apart.
The reason why some people do this automatically while others struggle is still unknown.

Shownotes Transcript

This week on Unexplainable or Not, we’ve got three scientific mysteries all about left and right. Jonquilyn Hill, host of Vox’s new podcast Explain It to Me), is going to guess which of them has been solved and which ones are still unexplainable.

Guest: S. Furkan Ozturk), researcher at Harvard University

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