Primo what?….read on!
My source is Wikipedia. http://en.wikipedia.org/wiki/Primogeniture
During the Roman Empire, Roman law governed much of Europe with little distinction between the oldest, youngest, male or female, if the deceased left no will. Roman aristocracy was based on competition and a family could not maintain its position merely through hereditary succession or having title to lands. The eldest son would carry the fathers name however he was expected to construct his own career.
Primogeniture is the right, by law or custom of the firstborn child to inherit the family estate. In the absence of children, inheritance passed to collateral relatives, usually males, in order of seniority of their lines of descent. The eligible descendants of deceased older siblings, takes precedence over living younger siblings.
There are many variations on Primogeniture including that which is based on Country of birth, Absolute primogeniture, Male-Preference cognatic primogeniture, Agnatic and a variation that allows women to succeed only at the extinction of all the male descendants in the male line called Semi-Salic law.
The earliest account of primogeniture known, involved Isaac’s son Jacob being born second, and Isaac’s son Esau being born first and entitled to ‘birthright’ but eventually selling it to Isaac’s second son Jacob, for a small amount of food.
Returning to the Roman period briefly, Roman emperors indicated their choice of successor, usually a close family member or adopted heir and the presumption that the eldest or even a natural son, was not enshrined.
In England, primogeniture was mandatory for inheritance of land. In law, primogeniture is the rule of inheritance whereby land descends to the oldest son. Under the feudal system of medieval Europe, primogeniture generally governed the inheritance of land held in military tenure. The effect of this rule was to keep the father’s land for the support of the son who rendered the required military service. When feudalism declined and the payment of a tax was substituted for military service, the need for primogeniture disappeared. In England, consequently, there was enacted the Statute of Wills (1540), which permitted the oldest son to be entirely cut off from inheriting, and in the 17th century military tenure was abolished; primogeniture is, nevertheless, still customary in England.
For Australian succession law, look to The Perth Agreement at the 22nd Commonwealth Heads of Government Meeting in 2011 that discusses further the proposed changes.