Equal in Dignity
Each human being is unique and different, but they all have equal dignity, because that is not dependent on size, intelligence, maturity, age, social status, or anything else, but on the fact that Man is the crown of creation, the only creature of God made in His image and likeness. We have rational souls, unlike the other creatures of Earth, and bear the image of God in ourselves. This is our dignity, and equally common to us all, thus we have equal dignity.
However, "equality" is not taken to mean this today; more often, it means "fairness," which is also a term that has become convoluted. If from the beginning we were distinctly different, male and female, for example, perhaps there was a reason for that! We have equal dignity, and different roles that pertain to our natures. We can each be suited for different tasks and also look physically different, without ruining the equality we possess in our human dignity.