As a nation state, Italy has emerged only in 1871. Until then the country was politically divided into a large number of independant cities, provinces and islands. The currently available evidences point out to a dominant Etruscan, Greek and Roman cultural influence on today's Italians.
In the Italian culture, how do they trace their family tree? In the U.S., it's usually done through the male line and their last name. Is it the same in Italy? If not, how do they trace their family tree?
There is not an Italian culture for genealogy.
Each person may trace it in a different way.
In my case I trace both the male and female lines through the last names.
I trace my ancestors, their siblings and their descendants.
I know some people that only trace the lineage (male ancestors with the same surname", other traces all ancestors but not their siblings....