Here are the possible solutions for human's earliest life stage clue
Answer
Clue
Relevancy
embryo
Clue
Human's earliest life stage
Human's early life stage
Definition
the entity which develops in a woman's womb until it is born as a baby, esp. up to about eight weeks, after which it is known as a foetus, also EMBRYON
eolithic
Clue
Related to the earliest period of human culture
Definition
of or like an eolith
onset
Clue
Earliest stage
Earliest stage, as of symptoms
Definition
a beginning
primeval
Clue
Like the earliest life forms
Definition
belonging to the earth's beginnings, also PRIMAEVAL
rumor
Clue
It could be spread human-to-human
fetus
Clue
Stage of human development after embryo
Definition
(Latin) the unborn in the womb with distinctly formed parts, also FOETUS