Lead poisoning probably did not cause the downfall of the Roman Empire

Lead doesn't taste bad, though. They say it tastes sweet, and I'm sadly old enough to remember the smell of leaded gasoline.

True for complex systems, but West Roman empire didn't "collapse" instantaneously, nor within a year/decade.

If I remember correctly what I read on it, the actual date is arbitrarily taken for didactic clarity, and it's the date the capital moved to another city. But the kingdom still called itself Roman, so contemporaries didn't quite notice the difference. BTW, this is how modern Romania got its name -- smaller kingdoms in the former empire called themselves the glorious Rome.

The curious detail is that Barbarian leaders actually wanted to become king of Rome and to be acknowledged as equally civilized, rather than merely sack and loot it. Some of them were actually legioneers, if I remember it correctly. So it's not clear if a legioneer sacked Rome and set himself as king, was the new state still Roman or already not.

Is that an answer to their first question, their second, or both?

Do you think the Roman empire was notably rational, and that if Constantine hadn't converted to Christianity it would have been more rational than it was under Christianity? That seems highly not obvious to me, and I would be interested in any evidence you have.

Early on, the dole was just grain. During the late empire, it was replaced by bread, wine, olive oil and pork. So clearly the costs were rising as the empire was approaching its end.

What effect the dole had on the economy seems to be somewhat disputed. Clearly, far-left/marxist academics will want to downplay any effect and liberterian/right wing academics will probably overstate the effect.

Descriptively, it is a fact that inflation started to become a big problem not long after Marcus Aurelius added wine and pork to the dole.

Clearly, there were other factors involved, especially corruption. In fact, I think all factors were contributing to the same net effect, they all reduced the number of people (especially free people) contributing to economically to the economy and specifically the economy of the state.

- Slavery drove down the price of labor, laborers lost their jobs.

- The dole kept the laborers from re-joining the labor market, either as workers or by starting businesses.

- Corruption limited tax income from the upper clases.

- The governement introduced an increasing number of inefficiencies in the economy, by debasing the currency, allowing tax-farming and limiting economic freedoms (for instance, workers were turned into serfs and price controls on goods were introduced). All of which reduced the supply side of the economy.

- A mercenary based military was expensive to maintain, and very unreliable when not paid.

Another way to see the factors above, is that as the population (both upper and lower classes) were granted privileges during good times, these were seen as irrevocable rights by an increasingly entitled populace, while the comprehension of what goods and services were needed to make these benefits possible was lost to most people.

Gradually, the state was running out of money, and had to debase the currency and increase taxes to remain solvent. Both types of actions would only privide temporary relief. The debasement caused inflation, and tax increases led to corruption going up and production going down.

Eventually, the government ran out of ways to continue to pay the mercenaries. At that point, it was too late to convince the idle citizenry to go back to productive work or to serve in the army, as that part of Roman culture had died out.

Eventually, the collapse had to come. As barbarians took control at the borders, the economy collapsed, causing massive unrest in the entitled population. Partisan groups started clashing in the streets. Invasions, civil wars, utilities (such as aquaducts) shutting down and eventually an unstable food supply caused disease, hunger and death. At first, the population was going down slowly, then quickly. Over a few centuries the population of 1 million had become 30000.

In a 1000 years, maybe historians will have the same discussions about Western Civilization's collapse. Was it smog from coal plants, corruption of the leaders, mass migrations or simply the whole population becoming lazy and entitled that caused the collapse?