He says animals like sponges are even more ancient, but they lack the bilateral symmetry that characterizes most animals today.

他表示，海绵等动更古老，但缺少现今大多数动的两侧对特性。

The scans confirmed the animals' bilateral body morphology and revealed the shape of the burrows they left from scavenging the seafloor.

扫描确认这些动的两侧对身体态，并揭示在海底觅食时留下的洞穴状。

Bilaterean body plans can be roughly divided into three sections.

两侧对的身体结构大致可以分为三个部分。

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

一般在动界，一旦进化出两侧对的身体结构，就不会再退回到不对的状态。

And you have to remember the signals, the yellow ones that are bilaterally symmetric might be just the ones that are offering the best rewards.

因此， 你必须记住这些信号，那些黄色且两侧对的， 可能正是提供最佳奖励的信号。

But starfish, despite being evolved from the same ancestors as other bilatereans, don’t seem to have an obvious tail, or head for that matter or clear symmetry.

但海星尽管与其两侧对动有着相同的祖先，却没有明显的尾巴， 或者说头部， 也没有清晰的对性。

And it’s an important piece of the puzzle when it comes to understanding bilaterean evolution and figuring out how strange creatures like echinoderms relate to creatures like us.

这对于理解两侧对的进化以及弄清楚像棘皮动这样的奇特与我这样的有何关联非常重要。

To settle the debate researchers mapped gene expression in different bits of starfish anatomy, looking specifically for the genes expressed in the forebrain, midbrain and trunk of other bilaterians.

为平息争论， 研究人员绘制海星不同部位的基因表达图谱，特别寻找在其他两侧对的前脑、中脑和躯干中表达的基因。