Section outline

  • Silhouettes depicting stages of human evolution from primates to modern humans.

    Can you watch evolution happening?
    ::你能看进化发生吗?

    Usually evolutionary changes occur at a very slow pace. Human evolution took millions of years. However, sometimes evolution can also happen quite quickly.
    ::进化变化通常以非常缓慢的速度发生,人类进化花费了数百万年时间,但有时进化也可能很快发生。

    Tracing Evolution
    ::追踪演变

    How fast is evolution? Can you actually see evolution happening within your lifetime? Usually evolution takes a long time. So how can we visualize how it has happened?
    ::进化的速度有多快?你真的能看到进化发生在你的一生中吗?进化通常需要很长时间。我们如何想象它是如何发生的呢?

    Rates of Evolution
    ::变化率

    How long did it take for the giraffe to develop a long neck? How long did it take for the Galápagos finches to evolve? How long did it take for whales to evolve from land mammals ? These, and other questions about the rate of evolution , are difficult to answer.
    ::长颈鹿长颈需要多长时间?加拉帕戈斯的鳍需要多长时间才能进化?鲸鱼从陆地哺乳动物中进化需要多长时间?这些以及其他关于进化速度的问题很难回答。

    The rate of evolution depends on how many of an organism’s genes have changed over a period of time. Evolution is usually so gradual that we do not see the change for many, many generations. The rate of evolution also depends on the generation time of a particular species .
    ::进化速度取决于一个生物体的基因在一段时间内的变化。 进化速度通常如此缓慢,以至于我们看不到许多代人的变化。 进化速度也取决于特定物种的生成时间。

    Not all organisms evolve at the same rate. Humans took millions of years to evolve from a mammal that is now extinct. It is very difficult to observe evolution in humans. However, there are organisms that are evolving so fast that you can observe evolution! A human takes about 22 years to go through one generation. But some bacteria go through over a thousand generations in less than two months. Some bacteria go through many generations in a few days. And sometimes a bacterial generation is as fast as 20 minutes! We can actually trace their evolution as it is happening.
    ::并不是所有生物都以同样的速度进化。人类花了数百万年的时间从哺乳动物进化而成,哺乳动物现在已经灭绝。很难观察人类的进化过程。然而,有些生物的进化速度如此之快,以至于你可以观察进化过程。人类需要大约22年的时间才能经历一代。但有些细菌在不到两个月的时间里经历了一千代的进化过程。有些细菌在短短的几天里经历了几代人。有时细菌的进化速度会达到20分钟。我们实际上可以追踪它们的进化过程。

    Evolutionary Trees
    ::进化树

    If evolution can take a very long time, how can we visualize how it happens? Charles Darwin came up with the idea of an evolutionary tree to represent the relationships between different species and their common ancestors ( Figure ). The base of the tree represents the ancient ancestors of all life. The separation into large branches shows where these original species evolved into new species.
    ::如果进化需要很长的时间,那么我们如何想象它是如何发生的呢?查尔斯·达尔文提出了进化树的概念,以代表不同物种与其共同祖先之间的关系(图)。树底代表着所有生命的古老祖先。将这些原始物种分成大树枝表明这些原始物种是如何演变成新物种的。

    The branches keep splitting into smaller and smaller branches as species continue to evolve into more and more species. Some species are represented by short twigs spurting out of the tree, then stopping. These are species that went extinct before evolving into new species. Other “Trees of Life” have been created by other scientists ( Figure ). If the evolutionary tree went back far enough to begin with the first living organism, what type of organism would that be? Animal , plant, protist , or none of those?
    ::随着物种继续演变成越来越多的物种,树枝不断分裂成较小和较小的树枝。有些物种代表着短小的树枝从树上跳出来,然后停止。这些物种在演变成新物种之前就灭绝了。其他“生命之树”是由其他科学家创造的(图 ) 。 如果进化树的距离足够远,可以从第一个生物体开始,那么哪种生物会是哪种?动物、植物、原生物体,或者这些生物都不存在?

    Two evolutionary trees illustrating species relationships and common ancestors in evolution.

    Darwin drew this version of the “Tree of Life” on the left to represent how species evolve and diverge into separate directions. Each point on the tree where one branch splits off from another represents the common ancestor of the species on the separate branches. Scientists have drawn many different versions of the “Tree of Life” to show different features of evolution. The Tree of Life on the right was made by Ernst Haeckel in 1879.
    ::达尔文在左边绘制了这个版本的“ 生命之树 ” , 以代表物种的演变和不同方向。 树上的每个点,其中一根树枝从另一根树分开,代表了不同树的物种共同祖先。 科学家们绘制了许多不同的“生命之树 ” , 以显示不同的进化特征。 右边的生命之树是1879年恩斯特·海克尔制作的。

    Summary
    ::摘要

    • Evolution is usually so gradual that we do not see the change for many, many generations.
      ::进化过程通常如此缓慢,以至于我们许多代人看不到变化。
    • An evolutionary tree can be drawn to visualize the relationships between different species and their common ancestors.
      ::可以画一棵进化的树来想象不同物种与其共同祖先之间的关系。

    Explore More
    ::探索更多

    Use the resource below to answer the following questions.
    ::使用以下资源回答下列问题。

    • Richard Dawkins: Why are there still Chimpanzees? at  (1:47)

      ::理查德·道金斯(Richard Dawkins):为什么还有黑猩猩?
    1. Are we descended from chimpanzees? Explain your answer.
      ::我们是黑猩猩的后裔吗?
    2. When reading an evolutionary tree, what does it mean if two species are very close on the tree?
      ::当阅读进化树时,如果树上有两个物种非常接近,那是什么意思?
    3. What does it mean if two species are very far apart on a tree?
      ::如果树上有两个物种非常相距甚远,那是什么意思?
    4. What five species comprise the Great Apes?
      ::什么五种物种构成大猩猩?

    Review
    ::回顾

    1. How fast is evolution?
      ::进化的速度有多快?
    2. What is the purpose of an evolutionary tree?
      ::进化树的目的是什么?
    3. Who came up with the idea for the evolutionary tree?
      ::谁想出进化树的想法?