17:28 13 September 2011
Colin Barras, biomedical and environment news editor
Stromatolites have been hanging around for ages (Image:Roger Garwood & Trish Ainslie/CORBIS)
It is five years since Richard Fortey retired from his post as senior palaeontologist at London’s Natural History Museum. Yet that has hardly curbed his academic output or the enthusiasm that drove him to study fossils for more than half a century. If anything, he is rapidly cementing his position as one of his field’s great survivors.
Fortey’s latest book is all about survivors too. Life has notched up something like 3.8 billion years on Earth, and it has been a rough ride. The average mammalian species, for instance, rarely makes it much beyond its millionth birthday before evolution ushers it out of existence by churning out a replacement species that’s an even better fit to its particular environment. Even species who survive this never-ending competition are likely to be snuffed out during a rare mass extinction event.
But the fossil record suggests that every so often evolution hits the jackpot: an organism so impeccably and robustly suited to its environment that further modification is apparently unnecessary. These ancient survivors count their time on Earth in the tens or hundreds of millions of years, and seem able to endure the bleakest of mass extinctions. Darwin had a name for them:living fossils. That peculiarly oxymoronic moniker, too, has survived - for around 150 years.
In Survivors, we are presented with some very long life histories. Take the stromatolites, unassuming microbial mounds found today in a few inhospitable places including Shark bay, a World Heritage area in western Australia. The layered mounds are virtually indistinguishable from fossils found in rocks elsewhere in western Australia - formed 3.45 billion years ago, when life had barely begun to secure a toehold on Earth. Such permanence is remarkable in anyone’s book.
Unfortunately, this longevity is rarely accompanied by beauty: these most ancient of survivors are often lacking in looks. Even Fortey confesses to momentary disappointment when, having travelled from the UK to Australia, he finally sees a living stromatolite.
Other species he encounters are similarly underwhelming in appearance. When he visits Hong Kong it is not in pursuit of some exquisite wild bird, but rather to plod through mudflats digging for worms and shells, including the brachiopod Lingula. There are many intricately whorled shellfish in this world, but as one of the few full-colour pictures in the book confirms, Lingula isn’t one of them. It looks a little like a badly bruised human tongue, and has looked that way for around 500 million years - long before such a thing as a human tongue appeared on Earth.
Perhaps it is because the most durable of survivors are so unimpressive in appearance that Fortey buries them in the middle of the book. We begin and end with far more charismatic - and younger - survivors, including lungfish similar to those found in 220-million-year-old rocks, and horseshoe crabs that have changed barely a jot in 450 million years. The latter appear on the front cover (perhaps inevitably, given that they are the closest living relatives to the trilobites Fortey spent many years studying). Horseshoe crabs are noteworthy for their blue blood - which seems only appropriate for an organism whose ancient looks make it as deserving of regal status as any in the animal kingdom.
This meander into and out of deep time - with leaps between unrelated branches of the tree of life - gives the book a delightfully rambling feel. It’s as if Fortey, free in his retirement to do as he pleases, has grabbed the opportunity to journey across time and taxonomy in a way that no academic tome on evolution would dare. Along the way he indulges in many fascinating asides, drawing on a career’s worth of anecdotes to keep us entertained.
Fortey’s curiosity to explore is undiminished. Seeing evolution’s survivors rarely satisfies him: wherever possible he is keen to touch, taste, hear and smell them too. (Horseshoe crab eggs taste so strongly fishy that they cannot be recommended, he notes.)
The innocent fun that his field can provide is evident in his accounts. One particularly important fossil outcrop he visits in Newfoundland can be explored only if visitors remove their shoes. Like children queuing for a turn on an inflatable castle at a village fete, Fortey and his guides obediently shed their footwear. For a palaeontologist, life doesn’t get much better than a sunny day in such surroundings, he says.
The abiding mystery of the book - one that even Fortey’s many years in palaeontology can provide no answer for - is quite what singles out an organism as a survivor-in-waiting. Conspicuous by its absence, too, is any suggestion that our own species might make the grade. In fact, Fortey’s repeated concern is that 100 million years or more of almost unchanged existence might not be enough to guarantee an ancient survivor’s passage even to the next century. The coiled nautilus made it through the extinction that wiped out the dinosaurs, but might not outlive a tourist industry that prizes its pearly shells.
Enduring survivors are likely to have the last laugh, though. Fortey’s epilogue on cockroaches, virtually unchanged for 300 million years and famously likely to be the sole survivors of a nuclear apocalypse, provides an unsettling reminder of our own species’ surprising fragility.
Survivors: The animals and plants that time has left behind
By Richard Fortey
Published by: Harper Press