Physically, mentally, emotionally or temperamentally.
So why did our founders say we shared unalienable rights equally?
Because our rights aren't granted or guaranteed by mere men. If they were they would be subject to whoever happened to be in power. Rights for humans were different under Stalin than they were under Eisenhower. That's because under Eisenhower they were protected by a constitution which asserted that rights were granted by a Creator. Under Stalin the "party" granted rights.
So here, as opposed to the USSR or communist China, our citizens are equal in the sense that our constitution guarantees equal protection of God given rights under the law. So the government theoretically doesn't have the authority to suppress your behaviour unequally because you're gay or black or uneducated or female or weak or old or not very skilled or worship Jesus Christ or Buddha.
But why if humans are not equal in any natural way would their Creator consider them to have equal rights? Its because we have equal VALUE in his eyes. We are his. No one has greater value than another. Any parent of a covey of children understands this principle. It is only the children themselves who see themselves as superior or inferior in some way to their siblings.