远古动物表明平行进化

AN UPDATED family tree of the animal kingdom could radically change the way we think about the evolution of species.

最近更新的动物界系谱树可能从根本上改变我们对物种进化的思维方式。

According to conventional thinking, simple animals, including sponges, jellyfish and corals, evolved step-by-step in a linear fashion into those with more complex bodies, such as mammals.

按照传统的见解，包括海绵、水母和珊瑚在内的简单动物按部就班发生演变，以线性方式形成像哺乳动物一样的更加复杂的生物体。

Now Rob DeSalle of the American Museum of Natural History in New York and his colleagues have challenged this way of thinking.

现在，纽约美国自然历史博物馆罗布·德萨尔乐及其同事对这种思维方式提出质疑。

The team analysed DNA and other molecular evidence across the animal kingdom, including tiny sea creatures called placozoans. They have found that the placozoans are the closest living thing to the ancestor of all animals.

这个团队分析了横跨动物界的DNA和其它分子证据，包括称为扁盘动物的微小海洋生物。他们发现，扁盘动物是离一切动物始祖位置最接近的活着的生物。 

More intriguingly, these simple creatures belong to a group of organisms that, as DeSalle's team discovered, evolved in parallel to those that later developed into humans.

引起人们更多好奇心的是，正如德萨尔乐研究小组发现的一样，这些简单动物属于这样一类有机体，它们与那些后来演变为人类的生物体是平行进化的。

Since this deep division was forged half a billion years ago, before animals developed nerves, the finding implies that the nervous system developed twice - evolving independently in simple organisms like jellyfish and also in complex animals.

由于这一位于深处的分枝是在动物神经系统发育之前即5亿多年前生成的，所以，这一发现意味着神经系统发育了两次——在水母似的简单生物，同样也在复杂动物身上独立演变。