1) The belief in natural rights resulted in the creation of the Bill of Rights. This Bill of Rights ensured early in America's history that certain rights would not be taken away by the US government. This includes freedom of speech, freedom of religion, right to protest, right to petition, etc.
2) African Americans were not considered equal when writing the Constitution. This is evident from the passing of the 3/5ths Compromise. This law stated that every 5 African American people counted as 3 towards a states population. Along with this, hundreds of thousands of African American men were enslaved at this time and did not have the rights mentioned in question number 1.
3) The idea of natural rights has changed dramatically since 1787. In today's society men, women, and all races have the same legal and political rights. This means that all citizens can vote and are protected equally by the US Consitution.