Depopulation as a primary cause of the fall of the western Roman Empire

In the concluding lecture of "The Early Middle Ages", Dr. Daileader
points out the shortcomings of the "fall" theories of both Edward
Gibbon and Henri Pirenne. Instead, he points to widespread
archaeological evidence of severe depopulation occuring between the
2nd and 7th centuries as the factor underming both the Roman economy
and the Roman military.

He stated that there was evidence of urban decay as early as 200 CE
with successive footprints of towns and cities growing smaller and
smaller. Although some of the urban population may have moved back to
the country, studies of laws dealing with deserted lands also became
increasingly more desperate from the 2nd century onward.

He admits climate change and increased warfare may have played a role,
but there is evidence that new diseases introduced during the second
century, measles and smallpox (probably from China), were devastating
even before the Bubonic plague made its first appearance in the 6th
century. The resulting deurbanization severely impacted such Roman
institutions as its educational systems.

Although he attributed the loss of organized institutions to
depopulation it still leaves the question of why there was a cessation
of tutorage among the elite unless they, too, became so impoverished
they could no longer afford tutors?

As for Pirenne's theory of economic collapse because of disruption of
trade routes by Islamic conquests, Dr. Daileader points out that
current research shows that trade was still quite active through the
Northern Arc via Viking traders. In fact, Daileader points out that
the number of major routes (via Russia) connecting the Mediterranean
with Carolingian Europe actually increased sixfold. He highly
recommended Michael Mccormick's book "Origins of the European Economy:
Communications and Commerce" that was published in 2001 as an
excellent study of this phenomenon.