The statement that "men and women are equal" is well and good as a principle of law, as an enlightenment value and societal goal, and so on. However I think that few forget how rooted this principle is in theism - the notion that all have equal dignity and are absolutely valuable becomes incomprehensible when our common divine origin is obscured.
But suppose we do just that, being good modern philosophers and not taking for granted theistic principle. Then, what can we say about the equality of the sexes, or the equality of anybody for that matter? In fact this is not a worthless question, for it re-asks the question from a strictly naturalistic standpoint, and could serve to say something (in a round-about way) about God.
Sub specie aeternis, I do not say that "Men and women are equal"; as an abstract principle it is empty and meaningless. Rather, I say that men and women live in an infinitely recursive alternation of natural superiority and irreducible complementariness. Naturalistically speaking no male and no female is ever in a relationship in which "equality" has any currency; rather, owing in part to the roles their sexes take in different stages of life, and in part to other reasons, there is always, always a differential, and one is always giving deference to the other. There is always a primary, a secondary, and owing precisely to this differential, a special and unique fruit of the interaction. Equality, in an abstract and numerical sense, kills fruitfulness; but infinitely alternating inequalities are the rich soil of civilization.
"Woman is not independent of man or man of woman in the Lord. For just as woman came from man, so man is born of woman; but all things are from God." 1 Corinthians 11:11-12