I'm pretty sure they're referring to the end of Roman slavery. Slavery was the foundation of the Roman economy, which wasn't true of Europe's economy again until the colonial period.

https://en.m.wikipedia.org/wiki/Slavery_in_ancient_Rome https://en.m.wikipedia.org/wiki/Slavery_in_medieval_Europe

Sure, but the end of Roman slavery was just the collapse of the economy. No one bought slaves any more so slaves became serfs - no longer sellable people but people tied to the land and coerced to work. That's hardly a sign of marvelous progress.

While still being a horrible situation serfs had significantly more freedoms than Roman slaves. Serfs were able to hold possessions, work for themselves, and did not have an owner that had complete freedom over them including killing them.

I'm unfortunately ignorant on history of serfdom in Western Europe, but serfs in Russia were effectively owned by landowners. Killings, corporal punishment, family separation were routine practices.

Roman slaves could own property including other slaves. They could be doctors, architects, teachers & other occupations that would be considered middle class today.

I would be really interested to read about the transition of slaves to serfs after the fall of Rome. Is this your own hypothesis or something that has been written about?

I think it was meant very much in the figurative way. In continental Europe, Roman society never really stopped, it just changed a lot. Even Goths and Lombards would try to "become Romans" as much as replace them, happily adopting titles and structures (with varying levels of success).

A big hindrance to seeing continuity is that popular knowledge of "romanness" is so focused on the late republican/early imperial era and there is surely not much visibly continuity between early medieval and a snapshot of the Roman state outdated by several hundred years.

Serfdom is just a mortgage by anyther name. Unless you own your house you are a serf too.

The start of European colonialism marks the end of the Middle Ages. Abolitionism was about abolition in the Americas, not Europe where it was largely replaced by serfdom in the Middle Ages. Slavery continues to exist in some forms today.

[1] https://en.m.wikipedia.org/wiki/Slavery_in_the_21st_century

Also following the end of slavery the British Empire used “Coolies” from India and Asia in various transportation and labour roles which were basically a transitionary role between slavery and free paid workers. So job-wise was somewhat similar to slavery, in practice, but largely voluntary at the source and paid in some form to their families or community rather than ‘stolen’ by slave traders. While also less constrained from leaving back to their home countries, which was still difficult and they were not compensated nearly enough.

https://en.m.wikipedia.org/wiki/Coolie