万物简史 第579期:生命的物质(5)（在线收听）

That is why it can be recovered from patches of long-dried blood or semen in murder investigations and coaxed from the bones of ancient Neandertals. It also explains why it took scientists so long to work out how a substance so mystifyingly low key — so, in a word, lifeless — could be at the very heart of life itself.

这就是人们在谋杀案调查中能从干涸已久的血迹或精液中，以及能从古代尼安德特入骨骼中提取出DNA的原因。这也解释了为什么科学家花了如此长的一段时间才破译出这样一种看似无关紧要的——一句话，没有生命的——神秘物质，在生命本身中却占据十分重要地位。

As a known entity, DNA has been around longer than you might think. It was discovered as far back as 1869 by Johann Friedrich Miescher, a Swiss scientist working at the University of Tubingen in Germany. While delving microscopically through the pus in surgical bandages, Miescher found a substance he didn't recognize and called it nuclein (because it resided in the nuclei of cells). At the time, Miescher did little more than note its existence, but nuclein clearly remained on his mind, for twenty-three years later in a letter to his uncle he raised the possibility that such molecules could be the agents behind heredity. This was an extraordinary insight, but one so far in advance of the day's scientific requirements that it attracted no attention at all.

作为一种已知的实体，DNA存在的时间之长超乎你的想像。可是，直到1869年，DNA才由一位任职于德国蒂宾根大学的瑞士科学家约翰·弗里德里希·米歇尔发现。在通过显微镜研究外科手术绷带的脓液时，米歇尔发现了一种他不认识的物质，他给它取名为核素（因为它寄居在细胞核里）。当时米歇尔只注意到它的存在，但核素显然在他的心中留下了深刻印象。23年后，在给他叔叔的一封信中，米歇尔提出，这种分子可能是隐藏在遗传背后的原动力。这是一个极具洞察力的观点，但是这个观点超出了当时的科学要求，因此根本没有引起人们的注意。

For most of the next half century the common assumption was that the material — now called deoxyribonucleic acid, or DNA — had at most a subsidiary role in matters of heredity. It was too simple. It had just four basic components, called nucleotides, which was like having an alphabet of just four letters. How could you possibly write the story of life with such a rudimentary alphabet? (The answer is that you do it in much the way that you create complex messages with the simple dots and dashes of Morse code — by combining them.)

在以后的半个世纪的大部分时间里，人们普遍认为，这种物质——现在被称为脱氧核糖核酸或DNA——在遗传中所扮演的充其量是一个微不足道的角色。它太简单了，主要由4个被称为核苷酸的基本物质组成。这就好比一个只有4个字母的字母表。你怎么可能用这区区4个字母编写生命的故事？（答案在很大程度上类同于你用莫尔斯电码的点和划——将它们串连起来——去写一封内容复杂的电报。）