living at the same time; contemporary
William Shakespeare and his fellow poet-playwright Christopher Marlowe were coeval, having been born in the same year, but Marlowe died young, while Shakespeare lived into his sixties.
com (equal)#aevum (age) (Latin)
COEVAL=CO+EVOLUTION so two things evolved at the same time sounds similar to co-evolve meaning EVOLVED OR BORN AT THE SAME TIME co-eval; eval means age. coeval means same age