Read the given passage and answer the questions that follow.
It is not an exaggeration to say that the question of where and when the Black Death, the deadliest pandemic ever, originated is one of the biggest mysteries in human history. After all, the Black Death was the first wave of the second plague pandemic of the 14th to early 19th centuries. It killed some 50-60% of the population in Europe, the Middle East and North Africa and an unaccountable number of people in Central Asia.
Different proposals, based on competing theories, have been put forward. But in 2017, I came across some records describing an intriguing medieval cemetery in Kara-Djigach, Chüy Valley, northern Kyrgyzstan, which I suspected may hold the key. As part of a multidisciplinary team co-led by Maria Spyrou at University of Tubingen, we have now investigated several specimens from individuals buried at that site – and come up with an answer. The idea that the Black Death originated in the east – territories overlapping, roughly speaking, Central Asia, Mongolia and China – dates back to the contemporaries of the pandemic in Europe and the Islamic world. The modern, academic Chinese origin theory dates back to at least to in 1756-8 and a publication about the history of Central Asia by French scholar Joseph de Guignes.
What is the theme of the passage?