这片森林保留了原始的地貌，树木可以追溯到远古时代。

This forest preserves its ___primordial landscape, with trees dating back to ancient times.

科学家们正在研究宇宙形成初期的原始物质。

Scientists are studying the ___primordial matter from the earliest stages of the universe.

科学家们在研究原始器官的形成过程。

Scientists are studying the formation of ___primordial organs.