"How could he be proconsul when he hadn't been consul yet? He is listed as praetor in "72 or 71," so shouldn't he have been propraetor in Spain?" ROMAHOST
The order of advancement through elected offices (magistracies) in Republican Rome was known as the Cursus Honorum.
The sequence of offices in the cursus honorum meant that an office couldn't be skipped, in theory. A Roman male of the upper classes became Quaestor before he could be elected Praetor. He had to be elected Praetor before Consul, but the candidate need not have been either an Aedile or Tribune. The Quaestor candidate had to be at least 28. Two years had to elapse between the end of one office and the beginning of the next step on the cursus honorum.
Originally,
the magistrates sought the advice of the Senate when and if they wished. Over time, the Senate, which was made up of the magistrates past and present, insisted on being consulted.
Quaestor
The first position in the cursus honorum was Quaestor. The term of Quaestor lasted a year. Originally there were 2 Quaestors, but the number increased to 4 in 421, to 6 in 267, and then to 8 in 227. In 81, the number was increased to 81.
The Assembly of the 35 tribes, the Comitia Tributa, elected Quaestors.
Tribune of the Plebs
Annually elected by the plebeian section of the Assembly of the Tribes (Comitia Tributa), known as the Concilium Plebis, there were originally 2 Tribunes of the Plebs, but by 449 B.C., there were 10. The Tribune held great power. His physical person was sacrosanct, and he could veto anyone, including another Tribune. A Tribune could not, however, veto a dictator.
Aedile
The Concilium Plebis elected 2
Plebeian Aediles each year. The Assembly of the 35 tribes or Comitia Tributa elected 2 Curule Aediles annually. It was not necessary to be an Aedile while following the cursus honorum.
Praetor
Elected by the Assembly of the Centuries, known as the Comitia Centuriata, the Praetors held office for a year. The number of Praetors increased from 2 to 4 in 227; and then to 6 in 197. In 81, the number was increased to 8. Praetors were accompanied by 2 lictores within the confines of the city. The lictores carried the ceremonial rods and axe or fasces that could, in fact, be used to inflict punishment.
Consul
The Comitia Centuriata or Assembly of the Centuries elected 2 Consuls annually. Their honors included being accompanied by 12 lictores and wearing the toga praetexta. This is the top rung of the cursus honorum.
Main Source: Marsh, Frank Burr; revised by H.H. Scullard. A History of the Roman World From 146 to 30 B.C. London: Methuen & Co. Ltd., 1971.