Memoirs of an evolutionary life

18 July 2012

From the place where Captain Cook first stepped out of his longboat onto Australian soil, Rudy Raff looked out onto the rock platform. As fronds of brown kelp rose and fell in the waves, he focussed on a carpet of purple sea urchins covering a ledge of sandstone.

It was 1985, and Raff was part of a group of scientists in the United States that had just forged the brand new field of evolutionary developmental biology - nicknamed evo-devo. And here, in Sydney's Botany Bay, he was looking at the very species of sea urchin - Heliocidaris erythrogramma and Heliocidaris tuberculata- that he hoped would provide missing puzzle pieces to understanding mechanisms of developmental evolution.

"I never would have guessed that on Sydney's golden shores, there'd be a pair of organisms that could revolutionise the study of marine embryo evo-devo," he said.

Raff, a Distinguished Professor in biology at Indiana University, describes this pivotal moment in his new book, Once We All Had Gills, in which he takes readers on a journey of some of the most vibrant and living examples of evolution on earth.

As one of the founding fathers of evo-devo and a leader in developmental biology, Raff uses his own growth as a scientist as a backdrop to paint a fascinating picture of evolution, and the weird and wonderful ways that scientific inquiry has helped us understand it.

The book's scientific tid-bits range from descriptions of how asteroid collisions millions of years ago and mile thick ice only thousands of years ago shaped his native Quebec, to the incredible evolution of life in Australia, to the intricacies of embryos, to the dynamics of anti-evolution in the public sphere.

Science for the public

Raff's choice to take an autobiographical approach for his first foray into popular science writing happened two years ago, when he decided to write a family history for his children that he thought would be "about 20 pages long."

But when he started writing, Raff realised that he was interested in saying a lot more. "I started to take seriously the notion that scientists should talk to non-scientists, because we really don't do it enough," says Raff. "We don't talk about why we do science, and why sciences like evolution are critical in a changing world."

Concerned that science denial, such as creationism, poses a threat to such public understanding, Raff felt urged to respond. So he decided to use an autobiographical narrative thread to write a publically accessible book about science, which was to be different from his previous professional books on evolution, "because with those, you're just talking to your colleagues," he says.

Founding of Evo-Devo

Raff's seminal books, Embryos, Genes and Evolution (1983) and The Shape of Life (1996), which are still being used by students today, focus on how genes and development influence evolution of animal bodies. After publishing the 1983 book, Raff says he realized that "although interest in evo-devo was growing, there was little experimental work on evo-devo itself."

Raff thought that the sea urchins he used in studying embryonic development could become an ideal experimental animal for delving into evo-devo because of how easily one could study their embryonic and larval development.

A transformative moment

In 1985, Raff's career would reach a turning point after giving a lecture on sea urchins to an audience that included the famous marine ecologist, John Pearse. "I talked to John after the lecture, and he said 'You should see this paper by Don Anderson in the Australian Journal of Zoology.' And he gave me a copy'," remembers Raff.

The paper was about Heliocidaris erythrogramma, a southern hemisphere urchin that was remarkable due to its unconventional mode of embryonic development. In the northern hemisphere, urchins had become textbook examples of development where the fertilized egg grows into an adult via a feeding larval form called a pluteus. But H. erythrogramma had done what Raff thought seemed impossible: it had evolved a different developmental path that dispensed with the pluteus altogether.

"I read Don's paper on the plane and it was a transformative moment, really a cosmic joke," he says. Raff immediately wrote to Anderson, head of School of Biological Sciences at the University of Sydney, asking to come out to see the urchins, and arrived in Sydney on New Year's Eve.

The Sydney sea urchins H. erythrogramma and its close relative H. tuberculata - a species that in contrast does form a pluteus - would go on to become the central experimental part of Raff's work in elucidating the profound evolutionary transformations that embryos could undergo in a geologically short time.

This 25-year journey would take him back to Sydney's School of Biological Sciences almost every year - equating to a full month's sitting in airplanes over the Pacific - and lead to adventures of finding evolutionary intermediates in larval evolution in Panama and to unravelling the mechanisms that created soft-bodied fossils of embryos and of creatures like the 550 million year-old fossils in South Australia's Ediacara Hills.

Raff says: "Our research has been extremely fun, and I hope that with this book, people will realise that there is excitement in science and relevance in understanding and preserving our world."