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Books

IN 1871, a now-obscure biologist called St George Jackson Mivart published . As its title suggests, the book was a riposte to Darwin’s theory of natural selection, published in 1859. Mivart had been an avid Darwinian, but the more he thought about it, the stronger his doubts grew. In particular, he couldn’t see how natural selection could account for the appearance of novel structures.

This was the start of a debate that has raged ever since: just what caused the major transitions in the history of life? How, for example, did birds evolve flight? Or animals evolve to live on land? The problem is that a small, incremental step towards structures such as wings, feathers or lungs would appear to be of little adaptive value, and so wouldn’t have been selected for by evolution. Ditto the sweeping anatomical and physiological changes required to take to the air or colonise the land. As the late palaeontologist and science writer Stephen Jay Gould put it, what use is 2 per cent of a wing?

Pretty much every major transition hits this problem, and creationists exploit it in their attempts to discredit the theory.

Neil Shubin at the University of Chicago is well placed to answer the question. As a palaeontologist, he predicted the location of, and then found, the fossilised remains of Tiktaalik roseae, a 375-million-year-old transitional form. Tiktaalik is what we used to call a missing link: it is an intermediate stage between aquatic and terrestrial animals, and one of the best pieces of physical evidence for the theory of evolution.

“As palaeontologist and science writer Stephen Jay Gould put it, what use is 2 per cent of a wing?”

The story of Tiktaalik‘s hard-won discovery in the Canadian Arctic was the centrepiece of Shubin’s excellent previous book, Your Inner Fish. His latest book, Some Assembly Required, plays to his other specialism, molecular biology, where he works to understand how genetics and developmental biology explain such major transitions – for instance, how a class of regulatory genes called Hox orchestrate the development of all body plans.

His new book is a skilful and fascinating account of how his two very different worlds produce a coherent answer to the 2-per-cent-of-a-wing question. Spoiler alert: evolution rarely comes up with anything truly new but simply repurposes what is available. Thus lungs evolved from swim bladders, feathers from dinosaurs’ insulating fuzz, and so on. When true novelty arises, it often comes from an unlikely source: viruses.

Shubin covers both the groundbreaking science and the scientists who broke it, telling a vivid and human story of the excitement, frustration and often sheer serendipity of progress.

Tiktaalik (and Shubin) also have a cameo appearance in another fine book by prolific author and palaeontologist Donald Prothero at California Polytechnic State University. Shubin and Prothero were university classmates and remain friends.

The buddies have produced very different books. Fantastic Fossils is an insider’s guide to finding, collecting, identifying and understanding fossils, including a comprehensive walk through the different life forms that fossil hunters might hope to unearth, from sponges to vertebrates.

There is a lot of ground to cover, but enough “wow” moments to keep you going, much like a real-life fossil-hunting expedition. Did you know, for example, that the earliest turtles had shells on their bellies rather than their backs? Or that the 15-million-year-old leaves in the fossil beds of Idaho are so exquisitely preserved they are still green? There is all this and much more to enjoy in both of these books.