Survivors
Geoscientist 21.09 October 2011
In his latest book Richard Fortey brings us a magical myth-busting tour of evolutionary survivors that have defied eruptions, impacts, ice ages and continental collisions for a very long time indeed.
Unlike “survival of the fittest”, “living fossil” was an original Charles Darwin coinage. He adopted “survival of the fittest” - it was irresistible – after Herbert Spencer gave it to the world 10 years later. Both terms, like the tenacious species so lovingly described in this magnificent book, have proved impossible to kill off.
From stupid creationist tracts to clever Guinness ads, evolution tends to be portrayed as linear; one form mutating into another, which replaces it; the implication being that ‘newer’ is intrinsically ‘better’. But evolution is a bush, not a ladder. Fortey seeks out the lungfish in Queensland, the horseshoe crab in Delaware Bay, and Lingula on Hong Kong mudflats and concludes: there’s nothing ‘inferior’ about such successful organisms, just because they claim old evolutionary origins.
Textbooks tended to repeat two glib mantras about living fossils. One was that they long ago reached ‘optimal adaptation’. (But what is so ‘optimal’ about a horseshoe crab?) The other was that they ‘lacked genetic variability’. This seemed plausible until, during the 1970s electrophoretic studies of DNA showed it to be nonsense.
Lineages naturally generate species at different rates. Statistically, some will sit at the low end of the range: “every bell-curve has its tail”, as Steve Gould put it. These will be rare, because low speciation is usually a recipe for extinction. But there will always be lucky ones. Lungfishes (three living genera) displayed wide variability hundreds of millions of years ago, and boasted many species. Growing morphological conservatism correlates perfectly with their falling diversity. Restriction and conservatism are two sides of the same coin.
But to survive, a species needs something else– habitat. Refugees need refugia. Fortey reveals how many biological stick-in-the-muds actually do spend their lives more or less stuck in mud - like Lingula. No past Earth, no matter how hostile, has ever lacked mudflats, where food supply is also never a problem. Living fossils are conservative, low diversity species, living in persistent habitats. It also helps, it must be said, not to ask too much of life.
Fortey’s intense, humane passion for everything that lives and has lived is amply proved on every page. This book demonstrates yet again that Fortey is, principally, not a scientist who can write, but a superb writer who happens to do science.
Reviewed by: Ted Nield
SURVIVORS – THE ANIMALS AND PLANTS THAT TIME HAS LEFT BEHIND
RICHARD FORTEY Published by: Harper Press; Publication date: September 2011;
ISBN 978-0-00-720986-6 (hbk)
List Price: £25 400pp www.harpercollins.co.uk