Bodie Hodge & Andy McIntosh give a good answer to a good question: How Did Defense/Attack Structures Come About? | Answers in Genesis.
Some great stuff from A.W. Pink’s Divine Covenants, in which he explains the importance of the doctrine of Federal Headship. Highly recommended, and well worth the read!
“It is of vital importance for a right understanding of much in God’s Word to observe the relation which Adam sustained to his posterity. Adam was not only the common parent of mankind, but he was also their federal head and representative. The whole human race was placed on probation or trial in Eden. Adam acted not for himself alone, but he transacted for all who were to spring from him. Unless this basic fact be definitely apprehended, much that ought to be relatively clear to us will be shrouded in impenetrable mystery. Yea, we go further, and affirm that, until the federal headship of Adam and God’s covenant with him in that office be actually perceived, we are without the key to God’s dealings with the human race, we are unable to discern man’s relation to the divine law, and we appreciate not the fundamental principles upon which the atonement of Christ proceeded.
“Federal headship” is a term which has almost entirely disappeared from current religious literature—so much the worse for our moderns. It is true that the expression itself does not verbally occur in Scripture; yet like the words Trinity and the divine incarnation, it is a necessity in theological parlance and doctrinal exposition. The principle or fact which is embodied in the term “federal headship” is that of representation. There been but two federal heads: Adam and Christ, with each of whom God entered into a covenant. Each of them acted on behalf of others, each legally represented as definite people, so much so that all whom they represented were regarded by God as being in them. Adam represented the whole human race; Christ represented all those whom the Father had, in His eternal counsels, given to Him. Continue Reading