Highly symmetrical bodies in animals might signal quality genes, and better offspring.

动物界存在的高度对称的体型可能代表着高质量的基因、以及更好的后代。

Generally in the animal kingdom, once you evolve a bilaterally symmetrical body plan you don’t go back.

一般来说，在动物王国中，一旦你进化出双边对称的身体计划，你就不会再回头了。

That is to say, a body plan with a head endand a tail end with a symmetrical body on either side.

也就是说，一个头部和尾部的身体计划，两侧身体对称。