expression, noun
most recent common ancestor
Technical term in evolutionary biology and genetics, referring to the most recent individual from which all organisms in a group are directly descended.
ヒトとチンパンジーの最も近い共通祖先は約700万年前に生きていたと考えられている。
The most recent common ancestor of humans and chimpanzees is thought to have lived about 7 million years ago.
共通祖先 means 'common ancestor' in general, while 最も近い共通祖先 specifies the most recent one.
A compound phrase: 最も (most) + 近い (close) + 共通 (common) + 祖先 (ancestor). A direct translation of the English term 'most recent common ancestor'.