ancestor

这种古代鱼类被认为是现代哺乳动物的祖先。

This ancient fish is considered an ___ancestor of modern mammals.

蒸汽机被认为是现代内燃机的前身。

The steam engine is considered the ___ancestor of modern internal combustion engines.

我的祖先来自一个古老的山村。

My ___ancestor came from an ancient mountain village.