primitive form

例句：

1. 1. The primitive form of the species was discovered in the fossil record.
   该物种的原始形态在化石记录中被发现。
2. 2. The primitive form of life on Earth is thought to have evolved from simpler forms.
   地球上生命最初的形态被认为是从更简单的形态进化而来的。
3. 3.The primitive form of this process has been observed in nature for millions of years.
   这一过程的原始形态已经在自然界观察到数百万年了。