Lastly, the purpose of the Birthright (#3):There must have been a reason to pass the birthright down and why it contained all the things promised. The reason can be found amongst the same verses that tell what the promises contain, i.e.:And I will bless them that bless thee, and curse him that curseth thee: and in thee shall all families of the earth be blessed. (Genesis 12)And in thy seed shall all the nations of the earth be blessed; because thou hast obeyed my voice.(Genesis 22)And they blessed Rebekah, and said unto her, Thou art our sister, be thou the mother of thousands of millions, and let thy seed possess the gate of those which hate them. (Genesis 24)And I will make thy seed to multiply as the stars of heaven, and will give unto thy seed all these countries; and in thy seed shall all the nations of the earth be blessed {Genesis 26)And thy seed shall be as the dust of the earth, and thou shalt spread abroad to the west, and to the east, and to the north, and to the south: and in thee and in thy seed shall all the families of the earth be blessed. (Genesis 28)In short, God created a people (family) for the purpose of blessing a fallen world, and it would be through these blessed people, and nobody else that this would be accomplished (both in OT and NT covenants, as the promises have elements of both).The apostle Paul saw the "seed" as Christ Himself, in whom, all people would be blessed, and he based that argument (esp in Genesis 22) on the fact that seed is singular tense. But in the context, one can see that the physical seed would be many as well, and thus the promises were talking about Abraham's descendants.That's the birthright in a nutshell and why God instituted it to carry out His plan---- the one (physical seed) and the multitudes of (physical) seed from Abraham's loins that would become many nations, with many kings, well blessed, and a blessing to all the world. In the book of Numbers, the prophet Balaam compares the number of the seed to a quarter of the world's population.