On the winter of 1934 during travel across Europe on board of the Orient Express Hercules Poirot, the famous Belgian detective faced the most intriguing and defiance case of his career: the murder of Mr. Ratchett. During the investigation Poirot reveals the real identity of the victim and the horrible crime that he committed in the past. Poirot also discovered that everyone on the coach had motives to kill Ratchett. With the help of Mr. Bouc, an acquaintance of Poirot and director of the company operating the Orient Express, Poirot arrives at two conclusions: first, a stranger boarded the train and murdered Ratchett; second, that all 13 people on the coach were complicit in the murder.
When Agatha Christie created this complicated plot in 1934, she never heard about the most perfect and yet mysterious death scene of all time: the Permo-Triassic extinction event. But that wasn’t her fault. Despite Cuvier’s notable remarks about massive periodic catastrophes or “revolutions” found in the fossil record, scientists only started to focus on the massive extinctions in the middle of the twentieth century.
The end-Permian extinction is the most severe biotic crisis in the fossil record. This great crisis occurred about 252 million years ago (Ma) during an episode of global warming. The extinction had a duration of 60,000 years. For years there was a great debate about the cause or multiple causes of this catastrophic event, so Douglas Erwin, in 1993, used Poirot’s second hypothesis to explain the Permo-Triassic event. He called this hypothesis “The Murder on the Orient Express Model”. But what forces converged to wipe out almost 97% of species on Earth?
At the Permian Period, almost all land masses were reunited in one single supercontinent: Pangea, which stretched from the northern to the southern pole. Due to the formation of this supercontinent, the habitable marine area was reduced and the climate showed severe extremes with great seasonal fluctuations between wet and dry conditions. Ten thousand years before the extinction event there was a spike of carbon dioxide in the atmosphere, that led to ocean acidification and warmer temperatures.
Massive volcanic eruptions in Siberia covered more than 2 millions of km 2 with lava flows, releasing more carbon in the atmosphere and high amounts of fluorine and chlorine increasing the climatic inestability. Warmer oceans, possibly had melted frozen methane located in marine sediments which pushed the global temperatures to higher levels.
Recently, a study analyzing rock samples from Meishan, China, pointed a new suspect: a microbe, called Methanosarcina. This microbe is related to a superexponential burst in the carbon cycle and a spike the availability of nickel. But, some scientist remain sceptical about when Methanosarcina actually evolved.
We are close to find the answer to the Great Dying, but thus far, the best possible explanation for this severe extinction still is: THEY ALL DID IT!
Agatha Christie, Murder on the Orient Express (1934), Collins Crime Club.
Douglas H. Erwin, Extinction: How Life on Earth Nearly Ended 250 Million Years Ago, Princeton University Press, 2006
Seth D. Burgess, Samuel Bowring, and Shu-zhong Shen, High-precision timeline for Earth’s most severe extinction, PNAS 2014, doi:10.1073/pnas.1317692111
Daniel H. Rothman, Gregory P. Fournier, Katherine L. French, Eric J. Alm, Edward A. Boyle, Changqun Cao, and Roger E. Summons (2014) “Methanogenic burst in the end-Permian carbon cycle,” PNAS doi: 10.1073/pnas.1318106111