By the fifth century AD (401-500 AD), things got so bad for the people living within Roman rulership that large numbers of them began to leave. A man called Salvian the Presbyter wrote about it this way:
Far and wide, they migrate either to the Goths or to the Bagaudae, or to other barbarians everywhere in power; yet they do not repent of having migrated. They prefer to live as freemen under an outward form of captivity, than as captives under the appearance of liberty.
As so a large number of people walked away from Rome. And it wasn’t only formerly productive people and slaves, quite a few nobles made deals with the northern tribes (often called “barbarians”), who were taking over Roman territory, piece by piece.
In 410 AD a group of these northern “barbarians” sacked Rome (defeated its armies and went through the city stealing a great deal of silver, gold and so on), by 476 AD the last official emperor was given a deal to leave and remain alive, and by 554 AD the city of Rome was in ruins. The eastern half of the Roman empire continued in an altered form for many centuries more, but the European half of the empire had lost its legitimacy, then lost its power, and fell apart, piece by piece.
This pulling-apart of the empire, however, didn’t affect the people living in those areas for very long. They had to evade the fights between the various armies, of course, and many had their food and animals stolen by those armies, but after the fighting stopped, they went back to their usual and productive ways.
Also as a result of the pulling-apart of the empire, the taxes that were extracted from the people fell substantially. This, obviously, was good for them, leaving much more of their money in their own hands, and in many places life got noticeably better: People had more food, built better buildings, and so on. The gigantic mansions of the Roman elite were torn apart, and their materials were used to build large numbers of comfortable houses for non-elites.
A clergyman and historian named Gregory of Tours noted this in about 590 AD:
The collectors of the tribute (taxes) had suffered great losses, since in the course of time the estates had been divided into small parts and the tribute could be collected only with difficulty.
Notice not just the tax losses, but that “the estates had been divided.” This means that the giant farms were divided into multiple small farms, and that many of the families who had been pushed out regained a decent piece of land and a decent way of life.
And as much as the “barbarians” (Goths, Visigoths, Franks, Vandals and many others) tried to keep things as they had been – as much as they wanted to become the new Roman elite – legitimacy had declined badly and people were doing what they thought was best for themselves, which wasn’t enough to sustain the barbarian kingdoms either. And so Europe decentralized, in most places down to the family level.
A historian named Robert Latouch noted this:
A state of anarchy prevailed in Gaul throughout the whole of the Merovingian period.
Gaul is the area of modern France, anarchy means “having no ruler,” and the Merovingian period ran from roughly 500 to 700 AD.
And so the western Roman empire split into smaller and smaller pieces, and the people living there were mainly left alone to do as they wished.
With the Roman government no longer ordering things and paying for them, the roads were no longer maintained and pirates came back to the Mediterranean Sea. These were difficulties, but people adapted: They transported goods by river rather than by road, and they moved their trading from the Mediterranean to the North Sea. Certainly there must have been a good deal of inconvenience involved, but life continued.
Here are two quotes from historian Chris Wickham on the quality of life through this period:
Cologne… was a major metal manufacturing center throughout the early Middle Ages; Paris was not only a fair but also had shops selling jewelry opposite Notre Dame in the 580s.
The North Sea in the eighth century almost certainly had more shipping than the Mediterranean.
Here are a few passages from archaeologist Peter Wells:
… a typical rural settlement of the sixth century, the houses were small and plain. There is no trace of any larger architecture, such as a leader’s house, a public assembly , or a ritual structure such as a chapel. But material culture is abundant and of good quality. Much of the pottery is decorated. Iron was readily available and was used to make a wide range of implements, including nails, belt buckles, and knives…
Like bronze, the fragments of ornate glass vessels show that the community had important outside contacts and had wealth to trade for imported luxury goods…
Their diet was diverse, and there is no evidence that their lives were unusually harsh. They had access to a wide range of craft technologies to produce objects they needed, as well as the ability to acquire luxury goods through trade with other communities.
Between A. D. 400 and 800, new craft industries expanded to include a variety of different materials… as the manufacturing systems expanded, so did the commercial networks through which the goods flowed.
And here, from 530 AD, is a man named Gildas reporting what he saw in Britain:
No sooner were the ravages of the enemy checked (that competing tribes stopped fighting), than the island was deluged with a most extraordinary plenty of all things, greater than was before known.
You can see from this image (depicting the trade routes of a somewhat later time) that the North Sea trade route connected much of Europe quite well, especially considering all the rivers, which are not included in this image.