Myths and misconceptions about evolution. Let's talk about evolution. You've probably heard that some people consider it controversial, even though most scientists don't. But even if you aren't one of those people and you think you have a pretty good understanding of evolution, chances are you still believe some things about it that aren't entirely right, things like, "Evolution is organisms adapting to their environment." This was an earlier, now discredited, theory of evolution. Almost 60 years before Darwin published his book, Jean-Baptiste Lamarck proposed that creatures evolve by developing certain traits over their lifetimes and then passing those on to their offspring. For example, he thought that because giraffes spent their lives stretching to reach leaves on higher branches, their children would be born with longer necks. But we know now that's not how genetic inheritance works. In fact, individual organisms don't evolve at all. Instead, random genetic mutations cause some giraffes to be born with longer necks, and that gives them a better chance to survive than the ones who weren't so lucky, which brings us to "survival of the fittest". This makes it sound like evolution always favors the biggest, strongest, or fastest creatures, which is not really the case. For one thing, evolutionary fitness is just a matter of how well-suited they are to their current environment. If all the tall trees suddenly died out and only short grass was left, all those long-necked giraffes would be at a disadvantage. Secondly, survival is not how evolution occurs, reproduction is. And the world if full of creatures like the male anglerfish, which is so small and ill-suited for survival at birth that it has to quickly find a mate before it dies. But at least we can say that if an organism dies without reproducing, it's evolutionarily useless, right? Wrong! Remember, natural selection happens not at the organism level, but at the genetic level, and the same gene that exists in one organism will also exist in its relatives. So, a gene that makes an animal altruistically sacrifice itself to help the survival and future reproduction of its siblings or cousins, can become more widespread than one that is solely concerned with self-preservation. Anything that lets more copies of the gene pass on to the next generation will serve its purpose, except evolutionary purpose. One of the most difficult things to keep in mind about evolution is that when we say things like, "Genes want to make more copies of themselves," or even, "natural selection," we're actually using metaphors. A gene doesn't want anything, and there's no outside mechanism that selects which genes are best to preserve. All that happens is that random genetic mutations cause the organisms carrying them to behave or develop in different ways. Some of those ways result in more copies of the mutated gene being passed on, and so forth. Nor is there any predetermined plan progressing towards an ideal form. It's not ideal for the human eye to have a blind spot where the optic nerve exits the retina, but that's how it developed, starting from a simple photoreceptor cell. In retrospect, it would have been much more advantageous for humans to crave nutrients and vitamins rather than just calories. But over the millenia,
对于进化论的迷与误解 让我们来谈谈进化吧 你也许听说 某些人认为它颇具争议 尽管大多数的科学家不这么认为 就算你不是反对者 并且认为自己相当理解进化的概念 你可能依旧相信着 一些不完全正确的想法 比如 “演化意谓着生物适应其环境” 这是一个旧想法 现在却成了早已被推翻了的 进化理论 就在达尔文发表其伟大的著作的 60 年前 让-巴蒂斯特·拉马克拉马克指出了 生物在一生中形成的 各种特征 并且将它们传给后代的现象叫做进化 就像,他认为 由于长颈鹿终其一生 都在拉伸自己的颈子吃树梢上的叶子 牠们的后裔便因此有了更长的脖子 但现在我们知道 基因遗传并非如此 事实上,生物本身不会演化 是随机的基因突变 使得有些长颈鹿 生来便有更长的脖颈 这使它们的生存几率 比那些不幸没有长“长脖子”的高了许多 这将我们引领到 “适者生存”的概念 这听起来就好像 进化总是偏好 最硕大 最强壮 或速度最快的动物 但事实并非如此 首先,进化的适存度 仅仅反映了生物是否适合当下的环境 如果所有的树木瞬间消失 只剩下青草地 那么所有的长颈鹿 都将处于不利的位置 第二,演化的延续仰赖的不是生存 而是繁殖 世上物种何其多 比如雄性的安康鱼 它们刚出生时又小又不适存活 必须迅速于死亡前 寻找到配偶 这样我们便可以说 如果有一物种没繁衍就死亡 那它在演化上就没什么用了是吧? 大错特错! 请记住,自然的选择并不 针对某些物种的个体 而是针对基因的层面 存在于某一个个体的基因 也会存在于其亲属身上 所以让生物牺牲自我 来帮助后代生存 或生殖的基因 其繁衍的数目可以大过于 仅仅在乎保存自我的基因 任何能使更多基因复制 并传给后代的机制 都可以达到这个目的 除了 进化的目的 关于进化论的一个最困难的概念就是 当我们说 “基因想要增加自己的数量” 或甚至 “自然的选择” 这些其实都只是比喻罢了 基因其实不愿做任何事 也并不存在一种外部机制 来选择哪些基因最适合保存 那真正所发生的是,随机的基因突变 会使生物个体 产生不同的行为或发展 而其中,有些行为 最后使得某些突变的基因被传到下一代 仅此而已 并不存在一个使物种进化 趋于完美的计划 比如:人的视觉神经 与视网膜的接触点 会产生不完美的盲点 但是人眼就是这样的 它从一个简单的感光细胞发展而来 回顾以往 人类如果能着重 营养和维生素的摄取 而不单单只摄取热量的话 那该有多好 但是我们祖先
during which our ancestors evolved, calories were scarce, and there was nothing to anticipate that this would later change so quickly. So, evolution proceeds blindly, step by step by step, creating all of the diversity we see in the natural world.
在这几百万年来的进化过程中 热量是很难取得的 而且没有任何人能预料 情况转变地如此迅速 所以演化的过程是盲目的 它一步 接着 一步 创造出我们至今所见到的 多样化自然界