According to the Cavalli–Sforza reconstruction of genetic history, there was little migration in Europe after the Iron Age. Most population growth can therefore be ascribed to the gradual expansion of local populations under conditions of improving fertility, rather than inter-regional transfer. That said, local migration from village to village may have been substantial; for the successful dedication and expansion of new settlements, it would have been necessary. The geography of the Mediterranean made this fairly convenient; at the beginning of the empire, about 750,000 Italians lived in the provinces. Julius Caesar, Mark Anthony and Octavian–Augustus settled many of their veterans in colonies, in Italy, and the provinces. Those established in Italy up to 14 BCE have been studied by Keppie (1983). In his account of the achievements of his long reign ("Res Gestae"), Augustus stated that he had settled 120,000 soldiers in twenty colonies in Italy in 31 BCE, then 100,000 men in colonies in Spain and southern Gaul in 14 BCE, followed by another 96,000 in 2 BCE. Brian Campbell also states "From 49 to 32 BCE about 420,000 Italians were recruited" – which would thus be the Veteran (citizen) stock that was largely sent to the provinces (colonies) during Augustus; The Lex Calpurnia however also allowed citizenship to be granted for distinguished bravery – as example the 1,000 Socii from Camerinum after Vercellae 101 BCE (Plutarch Mar. XXXVIII) or the auxiliary (later Legio XXII Deiotariana) after Zela. By the time of Augustus the legions consisted mostly of ethnic Latins/Italics and Cisalpine Gauls. Historian Theodore Mommsen estimated that under Hadrian nearly 1/3 of the eastern Numidia population (roughly modern Tunisia) was descended from Roman veterans.