Now that it is 2010 and the "Darwin Year" is over, we can expect the tide of evolution-themed documentaries and books to ebb. A notable exception, however (if I do say so myself), is my forthcoming book about evolution and the fossil record called Written in Stone. After years of hard work it will finally hit shelves on November 1, 2010. But before I get too carried away with self-promotion, I have to address a question that I have been asked many times during the writing process: "Do we really need another book about paleontology?"
The answer is an emphatic "Yes!" Even though numerous summaries of the overwhelming evidence for evolution have been published in the past year, the discipline of paleontology has often taken a backseat to genetics and microbiology. Fossils might demonstrate the fact of evolution, some authors imply, but to really understand how evolution works we need to look at living systems that we can observe right now. As Richard Dawkins wrote in The Ancestor's Tale, even if there were no fossil record at all, living organisms still would provide abundant evidence for evolution. Hence, in Dawkins' view, the fossil record is a non-essential "bonus" that is not truly necessary to understand how life has changed.
But I am not convinced by Dawkins' argument. During the 19th century, speculations about evolution (or a "natural law" that regulated the origin of species, as it was often referred to at the time) were heavily influenced by fossils. Not only had fossils confirmed that species could become extinct, but they also illustrated that life on Earth was composed of a shifting cast of actors that appeared and disappeared over time. This was particularly significant to Charles Darwin, who began the introduction to On the Origin of Species by explaining how the relationship between the living and fossil mammals of South America got him thinking about the "mystery of mysteries," evolution.
Even though Darwin deduced the mechanisms of natural and sexual selection from what could be observed among living organisms, the true power of his view of evolution was that all living things were linked together by common ancestry through a natural process that had operated over millions of years. What was observed in the present could be used to make predictions about the shape of the tree of life, and so the findings of paleontology have acted as a test of Darwin's ideas. At first many paleontologists felt that the fossil record did not accord well with evolution by natural selection, but during the past sixty years scientists have confirmed that Darwin was right about the pattern of life.
This is where many accounts stop, with paleontology acting as a sort of handmaiden to other evolutionary sciences, but there is much more to the story. Geology and comparative anatomy still make up the core of paleontology, but many researchers have been combining these more traditional aspects of the discipline with methods from genetics, microbiology, embryology and other sciences. Paleontologists are no longer just documenting transitions in the fossil record. They are using new approaches to explain how those transitions could have occurred.
Research published within the subdiscipline of dinosaur paleontology during the past year alone illustrates the spread of this synthetic approach. Last June paleontologists published a description of Limusaurus, a strange theropod dinosaur that may help explain a developmental shift in how the hands of dinosaurs and their bird descendants formed. Another team found degraded soft tissue material inside the bones of a different dinosaur, Brachylophosaurus, and the research drew upon microbiology and genetics as much as on traditional paleontology. And, since we know that birds are living dinosaurs, some paleontologists have even considered trying to reverse-engineer a chicken into something dinosaur-like by fiddling with genes the birds still possess. There are many more studies that could be mentioned, but this handful of examples illustrates how paleontology is becoming more of an interdisciplinary science that can provide new insights into how life evolved.
So while I will not dispute Dawkins' point that we could learn a lot about evolution by studying living creatures alone, I cannot so easily write off the fossil record as just a collection of curiosities. An understanding of the history of life on Earth has always been important to considerations about evolution. The interdisciplinary nature of many new studies has made paleontology more important than ever. No understanding of evolution is complete without a healthy appreciation for the fossil record, and I hope that my forthcoming book will help explain why so much of what we understand about evolution is written in stone.