That's not an estimate based on archaeological discovery, it's the classical date given by Varro Reatinus, which he took from Titus Atticus (I'm mentioning Varr

That's not an estimate based on archaeological discovery, it's the classical date given by Varro Reatinus, which he took from Titus Atticus (I'm mentioning Varro Reatinus simply because this timeline is now called the "Varronian timeline"). Titus Atticus came up with it based on various traditions and works available to him, but it's really just one of the dates that have been proposed by people in that age. It's the most common traditional date today largely because of a pretty complicated tradition of politics, and of legal and written works, that ends with Joseph Scaliger in the 16th century. It became, more or less, the "official" chronology used by the Roman state at one point, and it ended up inscribed on Augustus' Arch and on the Fasti Capitolini. But that's about it. In fact, it's likely that everyone even back then knew at least a good part of it was made up, since it was based on a bunch of traditional dates that didn't quite add up, and Tittus Atticus (edit: or Varro Reatinus? I don't remember which one) had to insert various "dark years" and "anarchic periods" in-between so that his chronology would match the timeline of consulships. It's hard to put a date on it, because Rome likely developed out of several villages in the region. The oldest arcaheological evidence from the area is way older than the 8th century BC. The Romans themselves didn't have anything other than a best guess about it, either (and several were put forth, not just this one). Edit: yep, I'm really fun at parties!