expression
oldest in human history; oldest known to mankind
Used attributively to describe the earliest known example of something in human history, such as evidence, artifacts, or records.
この洞窟壁画は人類最古の芸術作品とされている。
These cave paintings are considered the oldest works of art in human history.
人類最古の文字は約5000年前のものだ。
The oldest known human writing dates back about 5,000 years.
Compound of 人類 (jinrui, 'mankind') + 最古 (saiko, 'oldest'). The exact historical derivation is uncertain, but the expression is a straightforward modern coinage.