When the dog days of summer come to an end, one thing we can be sure of is that the school year that follows will see more fights over the teaching of evolution and whether intelligent design, or even Biblical accounts of creation, have a place in America’s science classrooms.

In these arguments, evolution is treated as an abstract subject that deals with the age of the earth or how fish first flopped onto land. It’s discussed as though it were an optional, quaint and largely irrelevant part of biology. And a common consequence of the arguments is that evolution gets dropped from the curriculum entirely.

This is a travesty.

It is also dangerous.

Evolution should be taught — indeed, it should be central to beginning biology classes — for at least three reasons.

First, it provides a powerful framework for investigating the world we live in. Without evolution, biology is merely a collection of disconnected facts, a set of descriptions. The astonishing variety of nature, from the tree shrew that guzzles vast quantities of alcohol every night to the lichens that grow in the Antarctic wastes, cannot be probed and understood. Add evolution — and it becomes possible to make inferences and predictions and (sometimes) to do experiments to test those predictions. All of a sudden patterns emerge everywhere, and apparently trivial details become interesting.

The second reason for teaching evolution is that the subject is immediately relevant here and now. The impact we are having on the planet is causing other organisms to evolve — and fast. And I’m not talking just about the obvious examples: widespread resistance to pesticides among insects; the evolution of drug resistance in the agents of disease, from malaria to tuberculosis; the possibility that, say, the virus that causes bird flu will evolve into a form that spreads easily from person to person. The impact we are having is much broader.

For instance, we are causing animals to evolve just by hunting them. The North Atlantic cod fishery has caused the evolution of cod that mature smaller and younger than they did 40 years ago. Fishing for grayling in Norwegian lakes has caused a similar pattern in these fish. Human trophy hunting for bighorn rams has caused the population to evolve into one of smaller-horn rams. (All of which, incidentally, is in line with evolutionary predictions.)

Conversely, hunting animals to extinction may cause evolution in their former prey species. Experiments on guppies have shown that, without predators, these fish evolve more brightly colored scales, mature later, bunch together in shoals less and lose their ability to suddenly swim away from something. Such changes can happen in fewer than five generations. If you then reintroduce some predators, the population typically goes extinct.

Thus, a failure to consider the evolution of other species may result in a failure of our efforts to preserve them. And, perhaps, to preserve ourselves from diseases, pests and food shortages. In short, evolution is far from being a remote and abstract subject. A failure to teach it may leave us unprepared for the challenges ahead.

The third reason to teach evolution is more philosophical. It concerns the development of an attitude toward evidence. In his book, “The Republican War on Science,” the journalist Chris Mooney argues persuasively that a contempt for scientific evidence — or indeed, evidence of any kind — has permeated the Bush administration’s policies, from climate change to sex education, from drilling for oil to the war in Iraq. A dismissal of evolution is an integral part of this general attitude.

Moreover, since the science classroom is where a contempt for evidence is often first encountered, it is also arguably where it first begins to be cultivated. A society where ideology is a substitute for evidence can go badly awry. (This is not to suggest that science is never distorted by the ideological left; it sometimes is, and the results are no better.)

But for me, the most important thing about studying evolution is something less tangible. It’s that the endeavor contains a profound optimism. It means that when we encounter something in nature that is complicated or mysterious, such as the flagellum of a bacteria or the light made by a firefly, we don’t have to shrug our shoulders in bewilderment.

Instead, we can ask how it got to be that way. And if at first it seems so complicated that the evolutionary steps are hard to work out, we have an invitation to imagine, to play, to experiment and explore. To my mind, this only enhances the wonder.

当三伏天要过完时，我们能确定的一个事情就是接着要来的学期会有更多有关进化论的教学的抗议，是否设计论或圣经的创造说在美国科学课堂上会占有一席之地。

在这些争议性话题中，进化论被当作一门抽象学科，它处理着地球的年代学或者讲述鱼最先是怎么样跳上陆地的。这种讨论好象是可选择的、离奇的或与生物根本无关的事情。争论的通常后果就是进化论从整个课程中下降了。

这是一个歪曲。

而且也很危险。

进化论应该教的，确实，进化论应该是生物课启蒙的核心。这样说基于下面三个原因。

其一，它朝代了有力的框架研究我们所生活的世界。没有进化，生物就只是一堆互不关联的事实，一套描述而已。让人吃惊的各种特性，从每晚狂饮酒的树鼩宝宝到长在南极荒场上的青苔，都不能得到调查和理解。加入进化论，才可以进行推论和預測，并且有时候可以做实验来验证这些預測。忽然间，花样到处出现，并且很明显，琐碎的细节也开始变得有趣。

进行进化论教学的第二个理由是这门课是此时此地就直接相关。我们对地球的影响使得其它生物体很快进化。而且我不仅仅是在谈论那些很明显的例子：昆虫对农药的广泛抵抗力，疾病抗体搞药性进化，从疟疾到肺结核；比如病毒导致禽流感的可能也进化成从人与人的传播方式。我们人家所具有的影响还要宽泛得 。

例如，我们打猎也可以使得动物进化。北大西洋鳕渔业导致鳕鱼的进化，使鳕鱼比40多年前成熟得更小更早。在挪威捕河鳟也导致这种鱼类也带来同样的变化。人类对大角绵羊战利性狩猎使这种大角绵羊进化为一种小角羊。以上种种又偶然地与进化预测相吻合。

相反，捕杀濒临灭绝的动物也会导致其原有被捕杀者物种的进化。有关孔雀鱼的实验就证明，没有捕食者以后，这些鱼进化的色彩更明亮，成熟得晚，较少扎堆在浅滩上，同时也失去了很快从某物上突然游走的能力。这种变化可以发生在5代以内。如果你接着又引入一些捕食者，鱼就会变得越来越少。

这样，没有考虑其它物种的进化也可能导致对物种保护不成功。同样，要保护我们自己免受疾病、害虫和食物短缺的伤害。总之，进化论并不是很远的抽象的学科。不能很好地教授这门学科可能会让我们对未来的挑战准备不足。

教进化论的第三个原因就更哲学一点。它考虑到对待证据的态度发展。“有关科学的共和战”，记者Chris Mooney雄辩地争论说，藐视科学证据，或任何形式的证据，充满在布什政府的政策中，从气候变化到性教育，从石油开采到伊拉克战争。对进化的不屑一顾是其普遍态度的主要原因。

此外，由于科学课堂本身就最先蔑视证据，因此也有争议说它是第一个需要培养的地方。一个意识形态不讲究证据的社会可能会出大乱子。这并不是说科学永远不会被左派意识曲解，如果有时候会这样，结果并不会更好。

但对于我来说，研究进化论的最重要的事情是一些更无形的事情。这就是说，一些努力包括深奥的乐观主义。这意味着，当我们遇到一些本质上复杂神秘的事情时，如细菌的鞭毛或萤火虫发现的光时，我们并不需要尷尬地耸肩。

相反，我们可以问问怎么会这样。如果最初看止去很复杂以至于很难理解进化的步骤，我们欢迎大家来想象、游戏、实验和探究。照我的看法，这只会增强好奇。