Sunday, April 21, 2013

Wonderful Life: The Burgess Shale and the Nature of History - Stephen Jay Gould

Stephen Jay Gould’s Wonderful Life: The Burgess Shale and the Nature of History is both a brilliant history of the Burgess Shale fossils and its discoverer Charles Doolittle Walcott, and an in depth look at the zoology of the animals behind the fossils. However, this book is not an easy read in many ways and is certainly not for the faint of heart. Gould does not hold back on the zoology. He bandies about scientific terms and evolutionary debates as though every potential reader has at least a Bachelor degree in biology. Yet despite of my own background in invertebrate zoology and taxonomy, there was a period of time where I put the book down and wondered, “Why am I pushing myself to read this?”. Perserverence is key, as by the time Gould wraps up the book all of the time spent learning about the work done in the 1970s on these fossil animals makes perfect sense.

Gould proclaims the Burgess Shale the most important fossil bed in the world as it was the first major find of fossils of soft-bodied creatures from the period just after the pre-Cambrian explosion 570 million years ago. The Cambrian explosion itself is important as it “marks the advent (at least into direct evidence) of virtually all major groups of modern animals – and all within the miniscule span, geologically speaking, of a few million years”. For Gould, the story of the Burgess Shale is interesting on a human scale from where classification of the fossils began with Walcott, the discoverer, and where it ended up with the reexamination by Harry Whittington of Cambridge University.

When Walcott discovered the Burgess Shale in southeast British Columbia during a field season in 1909, he was the head of the Smithsonian Institution in Washington, DC. Walcott’s commitments to administrative tasks led to years of putting serious research into his Burgess fossil collection on the backburner. He published a few preliminary papers, and a few monographs on some of the sponges and algae but none on the more complex animals. Unfortunately Walcott was not able to spend more time with his fossils during his retirement as he died shortly after it began.

After his death, Walcott’s wife prevented any serious study of the Burgess Shale fossils, primarily as she believed no one was up to the task. The massive fossil collection languished on high and out-of-the-way shelves in the Smithsonian. No paleontology student or research was likely to come upon them and have a eureka moment that would launch them into a lifetime of research, further pushing the Burgess Shale fossils to the back of every paleontologist’s mind. It was not until 1959 that one of the first major post-Walcott publications on Burgess Shale arthropods appeared. Leif Stormer, a Norwegian paleontologist, created a classification scheme published in the collectively written “Treatise on Invertebrate Paleontology”. Stormer’s classification was entirely different from Walcott’s, bringing nearly all arthropods into the same grouping as trilobites based on what he saw as similarities in their primitive appendages.

It was with Stormer’s classification that Harry Whittington, a paleontologist out of Cambridge University, and his two grad students, Derek Briggs and Simon Conway Morris, began their own intensive study of the Burgess Shale fossils. Much of this book is a discussion of the dilemmas thrown up during fossil study. Whittington started with an analysis of Marrella splendens as it is by far the most abundant fossil in the Burgess Shale. Walcott, in 1912, admitted that Marrella was not a conventional trilobite, but still placed it in the class Trilobita even as some of his contemporaries expressed their doubts. However, even these doubters did not stray from the notion that all of the Burgess fossils should fit into classification groups already known, even if they did not seem to fit. In 1971 Whittington knew that Marrella was different, but even he felt constrained by the belief that Burgess fossils were old yet primitive versions of modern species, and to keep Marrella in the Class Trilobita despite evidence that suggested otherwise.

For example, when he was working on reconstructing Marrella’s head with its appendages, he came up with a very different configuration than Walcott. In fact, Stormer had also seen differences in his own reconstructions compared to Walcott, and had decided to ignore the head when making his classification (instead concentrating on leg structure). Upon studying the illustrations Walcott had made of Marrella’s head, Whittington noticed that they had been retouched to the extent that they were essentially falsified, showing mouth part features that were not there. Despite these differences, and those Whittington noticed in the legs, Gould writes that “on the brink of a transforming insight he chose caution and tradition this one time – and placed Marrella in Stormer’s Trilobitoidea…yet as he did so felt the pain of betraying his own better judgment.”

Regardless, this first study and its conservative conclusion by Whittington eventually led to a revolution in classification of the Burgess fossils. The third Burgess fossil Whittington worked on, Opabinia, was what Gould calls a “eureka moment” in this restudy. By dissecting one of the ten fossil specimens of this organism, Whittington found that Walcott had been mistaken in his classification: it did not have the right leg appendages to be classed as an arthropod, nor did it have any features that would classify it in any of the known groups. It was an orphan. Finally, Whittington was able to free himself from the constraints of fitting a specimen into the existing scheme, and could simply describe an organism as he saw it, writing in his monograph, “My conclusions on morphology have led to a reconstruction which differs in many important respects from all earlier ones.”

The more Burgess organisms Whittington’s team investigated, the more they confirmed that Burgess organisms in the Cambrian showed body plans beyond the range of those seen in later times. There was tremendous diversity and disparity at the time, and as evolution proceeded this was whittled down to fewer different body plans in fewer different groups of organisms. These reclassifications of Burgess fossils are significant, as they demonstrate how the beliefs and world view of society or the paleontologist of the time can affect how the fossils are seen to fit in to the evolutionary record. More generally, how the personal views of a scientist can affect their interpretation of a revolutionary scientific idea. Gould associates Walcott’s “shoehorn” of Burgess fossils into existing taxonomical groups with his traditional, conservative, political, social and religious beliefs.

The remainder of the book is an exploration of this as Gould postulates evolutionary “what if” scenarios that challenge the notion that there is only one way to think about the progression of life, based on preconceptions of scientists like Walcott. Gould ends up reminding us that we should not let ourselves be led into thinking that there is only one path to take, one choice, one way of doing things because it is the one that we are willing to accept based on our expectations or comfort level. We need to explore what is possible, and be willing to accept even the most revolutionary idea, the most revolutionary change.

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