A molecule whose presence in ancient rocks is regarded as evidence of the existence or early development of life; (in extended use) a molecule regarded as representing a feature of an earlier stage in development or evolution.
Origin
1960s.
Definition of molecular fossil in US English:
molecular fossil
noun
A molecule whose presence in ancient rocks is regarded as evidence of the existence or early development of life; (in extended use) a molecule regarded as representing a feature of an earlier stage in development or evolution.