Asian tree rings explain historical plague outbreaks in Europe
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wsl.ch
1. Their conclusion is unverifiable. Science is about hypothesis, experiment, and falsification in a reproducible context. When someone says, "I can look at these tree rings and tell you whether rats or marmots spread the plague," I say, "Cool! Show me the results." And when they say, "What do you mean results? I just mean that we infer from the rings to the marmots," then I say, "Okay, well I just infer from planetary alignments to mood swings." Speculation is part of science. Speculation is not science.
2. An extremely strong inference is, by definition, acceptable without further evidence. You don't have to show me an experimental result if you can show me a strong logical case, with very strong causal or inferential links from one piece of evidence to the next. Although you can't reproduce for me a precise result showing that the Grand Canyon was the result of many, many millennia of erosion, you can show me over observable spans of time the general erosion rates in soil of that type with rainfall of that type and I'll accept your inference that many millennia were involved in the Grand Canyon. But tree rings in Asia to disease vectors in Europe? Give me a break.
[...] Moreover, their results challenge the long-standing, but poorly substantiated view that Yersinia pestis must have had a permanent wildlife reservoir in Europe, such as the urban black rat. Instead, new strains of the disease may have been frequently imported from Asia.
Nevertheless, an ultimate confirmation of this hypothesis depends on the availability of appropriate genetic material of ancient plague victims not only from different periods throughout time but also from different parts of Eurasia. The advent of aDNA techniques and international research collaboration across disciplinary boundaries will most likely be able to shed new light on this fascinating topic at the interface of human history and environmental variability.
We've already reconstructed Yersinia pestis strains from victims of the Black Death and the 6th Century Plague of Justinian....