Editing Openai/69387669-585c-8006-99a6-cf3a14ca3aad (section)

=== 🧩 A. The Traditional View: Black Rats as the Main Vector ===

The classic model:
* Rattus rattus thrives in urban environments
* Flea species (Xenopsylla cheopis) jumps from dying rats to humans
* This produces bubonic plague

This model fits many outbreaks, especially in:
* India (1890s)
* China (late 19th c.)
* San Francisco (1900)

But the medieval case is increasingly questioned.

==== 🔍 B. Problems With the “Black Rat Did It” Theory ====

===== 1. Rats are almost absent from medieval urban archaeological layers =====

Recent zooarchaeology shows:
* Many European cities before 1500 had far fewer black rats than assumed.
* In much of northern Europe, they barely appear in bone assemblages from the 11th–14th centuries.

This undermines the idea of ubiquitous rat-driven spread.

===== 2. The plague spread far too fast for normal rat-flea epidemiology =====

Typical rat-flea transmission spreads:
* a few kilometers per week

But the Black Death spread:
* up to 30–40 km per day
* across thousands of kilometers in a single year

Much faster than any rat-based model.

Human fleas or lice may have played a major role.

===== 3. Climate doesn’t align with a rat-origin model =====

Rat populations decline in:
* cold northern climates
* high altitudes
* certain rural environments

Yet plague devastated:
* Norway
* Sweden
* Iceland (indirectly)
* Alpine villages

These regions were not suitable for large black rat colonies.

==== 🐛 C. Alternative Theory: Human Ectoparasites ====

Studies (2017–2024) model plague transmission via:
* Human fleas (Pulex irritans)
* Human body lice (Pediculus humanus)

These models:
* match the rapid medieval spread
* fit mortality patterns
* explain transmission where rats were scarce

This theory is increasingly influential.

==== 🐀 D. So were rats irrelevant? ====

Not irrelevant, but:

===== ✔️ Rats played a major role in Mediterranean port cities =====

Warm climates → abundant rats → classic rat-flea cycles.

===== ✔️ Rats played a minor or negligible role in much of northern Europe =====

Other vectors were needed to fit the data.

===== ✔️ Mongol-linked reservoirs in Central Asia were primary =====

European rats were secondary amplifiers, not the origin.