By around 200,000 years ago, there were a few early humans living in Italy. We know about them from their flint axes, and from one of their villages that has been excavated west of Rome at Torrimpietra. These were not modern humans, though, but a different species of human called Homo Erectus. More Homo Erectus people, Neanderthals, lived near Rome around 100,000 years ago.
But the first people who were genetically the same as modern Italians, Homo Sapiens Sapiens, came in the Upper Paleolithic (the Old Stone Age) about 10,000 BC. These people’s DNA shows that they came to Italy from West Asia. They left some more stone tools, and some engravings of animals on cave walls and on bone, but nothing as fancy as the great cave paintings of France and Spain at this time. There must still not have been very many people in Italy.
There was a big change about 5000 BC when Neolithic (New Stone Age) people arrived in Italy. They seem to have come from Greece, in boats across the ocean, and they already had New Stone Age technology when they arrived: they knew how to farm and how to make pottery and build houses. They brought wheat with them, and cows, and sheep. Apparently they domesticated European pigs for themselves. They dug ditches around their villages in southern Italy to protect themselves from wild animals and strangers.
The bones of people from one of these villages, Ripa Tetta, show some interesting things: women in this village had their teeth pulled out on purpose, maybe to make themselves more beautiful (like getting a lip piercing or binding your feet). In general, they had terrible cavities in their teeth, from living so much on bread and porridge and beer. There was a lot of violence and broken bones in the village, among both men and women. But in other ways they were healthier than later people: they got a lot of exercise through walking around, and they lived in such small groups that they didn’t catch many infectious diseases.
By about 3500 BC, in the Late Neolithic, these people had gradually spread into northern Italy, even up into the Po valley. But a warming trend shortly after that made southern Italy too dry to farm, and so they gradually abandoned southern Italy and moved to the north. Some of them settled near Rome.
The Romans: From Village to Empire, by Mary Boatwright, Daniel Gargola, and Richard Talbert (2004). Okay, it’s a little dry, but it is up to date and has all the facts you could want.
The Journey of Man : A Genetic Odyssey, by Spencer Wells (2004). Traces the genetic history that shows when people came to Italy, among other things.