John A. Long's "The Dawn of the Deed"

John Long is vice president of research and collections at the Natural History Museum of Los Angeles County. His books include Frozen in Time: Prehistoric Life of Antarctica and The Rise of Fishes.

He applied the “Page 99 Test” to his new book, The Dawn of the Deed: The Prehistoric Origins of Sex, and reported the following:

Page 99 of my book starts a new chapter with the intriguing title of “Finding the Daddy Fish”. It implies that some fishes have ‘daddies’ and that it is worth the effort of finding them and writing about it all. In reality we set out on a mission to find the world’s oldest father as pertaining to the radiation of jawed animals. We were searching collections of well-preserved fossil placoderm fishes, amongst the oldest and most primitive of all jawed backboned creatures (vertebrates). What we set out to find was the origins of sexual dimorphism, when fishes first developed distinct male and female body parts for the act of mating by copulation. For us, finding the daddy fish implied that we would find the oldest known male genitalia in fishes of this age.

We did find it, and as the chapter reveals, like many discoveries in science, it was for me a totally serendipitous event. In fact the specimen showing the male organ was one my student had prepared and studied, but together we both missed the obvious feature that was there right under our noses. When it was identified by my colleague Per Ahlberg it was a big surprise and netted us another paper in the prestigious journal Nature (August 2009). What Per found was an elongate bony extension of the pelvic fin that equates to the cartilaginous male claspers in living sharks. Our earlier discovery of the world’s oldest unborn embryos inside female placoderm fishes was the first sign of gender in these peculiar little fishes. That discovery pushed back the evidence for live birth in vertebrates by almost 200 million years, even making it into the Guinness Book of World Records (p54, 2010 edition).

Page 99 also tells us that “we are fortunate to serendipitously uncover rare glimpses of the past lives of extraordinary people, led there by the need to find out information on very obscure topics”. This relates to the story of a true renaissance man, Dr Harold Leigh Sharpe, who worked primarily as an parasitologist studying minute little crustaceans called copepods. He then became interested in how they entered shark bodies, so devoted many years dissecting and electrifying shark male mating organs (claspers). He wrote the definitive leading works on the anatomy and function of shark claspers, but also he composed classical music and wrote some 11 symphonies. What a guy! I hope this insight from page 99 whets your appetite to read more of my book.

Learn more about The Dawn of the Deed at the University of Chicago Press website.

--Marshal Zeringue