The Hunt for the Golden Mole (27 page)

Hennig's big idea was a scoring system designed to show just how closely related various species, or groups of species, actually were. It is not just a matter of counting points of similarity – that might lead you to put whales in the same clade as fish – but rather of deciding which characteristics are the ones that matter. Crudely simplified, it means distinguishing between characteristics in their most primitive, ancestral state (
plesiomorphous
, if you want the technical term) from the derived or advanced (
apomorphous
) states that have been passed down the line. It is these derived characteristics which contain the ‘phylogenetic signals' and mark out family relationships. Simplifying further, it allows scientists to distinguish between species that are genuinely related, and those which have developed similarities – long probing snouts, powerful digging claws, dense waterproof coats, for example – simply through sharing similar environments. As an entomologist, Max takes his example from the world he knows best. ‘If you look at swimming insects,' he says, ‘they all look very similar. They all have fringes of bristles along the legs,
they all have some kind of water-repelling structures, and they all have some kind of air-carrying structures.' Usually, however, they have developed these characteristics independently and have not inherited them from common ancestors.
Lost
characteristics can be just as misleading. ‘Under a Linnaean system,' says Max, ‘flightless birds might all be put together as a group, whereas it may be that many birds that have appeared on oceanic islands have lost the ability to fly without in any way being related to one another.'

All this bears directly on nomenclature. At the time Linnaeus was devising his binomial system, most educated people in western societies would have known a smidgen of Latin. In every way, it made good sense. Having a shared academic language eased the problem of international communication. Everyone, or everyone who needed to, knew that
Homo
meant ‘man', and
sapiens
meant ‘wise'. The
sapiens
bit might be arguable, but Latin speakers knew their species from their genus, and understood clearly what was being said. In the twenty-first century even scientists tend to know Latin only by rote. For this reason, and because of the increasing participation of scientists using different alphabets, it is often suggested that the ponderous and often difficult binomials should be replaced with alpha-numerical codes that would be better understood by computers. It is hard to see this happening. ‘We have close to a million species already assigned Latin names,' says Max, ‘so any attempt to change the system would require absolutely vast retrospective work, taking lifetimes.' It is also alien to the human instinct for naming things. Not even a scientist would want to refer to number 53471c, rather than, say,
Brachytarsomys villosa
, or the hairy-tailed tree rat.

The number of taxonomic levels – main branches on the tree – has multiplied since Linnaeus, whose
genera
(plural of
genus
,
the groups into which related species are placed) were extremely large. Again Max takes his example from insects. ‘He had the genus
Papilio
, in which most of the butterflies were placed. Nowadays
Papilio
is only a group of swallowtail butterflies, and most of the others are in different genera because people have become aware of more species, and more differences, and as we've got more species we've had to come up with more categories in order to explain those differences. Since Linnaeus, people have been chopping the genera up smaller, and introducing other levels of classification.' At the end of my one-man seminar he lends me an undergraduate-level primer on the principles of taxonomy, which themselves seem to be evolving faster than any of the species under review. Armed with this, plus Joe's thesis and other learned volumes from various (mostly American) universities, I begin to construct some kind of basic understanding.

At the first level, life is divided into kingdoms. Linnaeus recognised just two – animals (
Regnum Animale
) and plants (
Regnum Vegetabile
). Two and a half centuries of exploration, analytical sophistication and genetic science have added four more – fungi, bacteria, archaea (single-celled micro-organisms) and protoctista (aquatic organisms including algae, seaweeds, protozoa and slime moulds). The kingdoms are then subdivided into
phyla
(plural of
phylum
), according to their basic characteristics. There are a great many of these, but the most important from the perspective of a mole-hunter are the
Chordata
– broadly, creatures with a spinal cord. Phyla are then split into classes. In animals there are six – mammals, birds, fish, reptiles, amphibians and arthropods (creatures with more than four jointed legs, including insects, spiders and crustaceans), each placed within the appropriate phylum. The classes then break down into
orders
. Typically there is no firm consensus
about the exact number of mammalian orders, their names, and which species belong where, but the number seems to hover around twenty-six. They include, for example, the self-explanatory
Carnivora
,
Rodentia
and
Primates
, though of more particular interest to us is the order
Afrotheria
, which includes the golden moles.

Orders then separate into
genera
, or families, and the genera into species. It is these two last, genus –
Homo
– and species –
sapiens
– that comprise the scientific name. Humans therefore share with golden moles their kingdom (
Animalia
), their phylum (
Chordata
) and their class (
Mammalia
), but diverge at the level of
order.
As relationships go, it's pretty remote. Other relationships are becoming more or less distant as DNA testing and molecular biology are reshaping the tree. Branches are lopped off, turned upside down and grafted back on different boughs. Golden moles, it turns out, are perfect examples of the unreliability of the old Linnaean method of grouping lookalikes. Their appearance, habitat and behaviour all so closely resemble the European mole's that their family relationship is obvious – obvious, that is, but wrong. In phylogenetic terms their shared common name could hardly be less appropriate.

False gold – European moles trapped in an English garden. The pale one is the colour of marmalade, but no relation to the golden moles of sub-Saharan Africa

The European mole, plague of field and garden, belongs to the order
Eulipotyphla
, which also contains the shrews (
Soricidae
) and hedgehogs (
Erinaceidae
) as well as forty-two species of ‘true' mole (
Talpidae
). Golden moles are of the order
Afrotheria
, which contains several other species that bear misleadingly strong resemblances to the
Eulipotyphla
. Madagascan tenrecs, for example, could easily double for European hedgehogs. But the golden moles are acquiring relations as well as losing them. Elephant shrews, for example, were first described in the 1880s and given their common name because they looked so much like all the other known shrews – long noses, sensitive whiskers and an appetite for worms and insects. In the 1990s, however, it was revealed by genetic sequencing that they were not shrews at all but twigs on a faraway branch that contained not just golden moles, tenrecs and aardvarks but was a near neighbour of some of the most improbable relatives it is possible to imagine – manatees, dugongs, hyraxes, marsupials and elephants. It was not that European and golden moles had descended from a common ancestor, but rather that natural selection had adapted them to their similar environments, a perfect example of what scientists call
morphological convergence
. As Max says, physical similarity very often
is
a good indicator of family relationships (horse, donkey, zebra, for example, or the cat family), but you can see how unknowingly difficult life was for scientists like Linnaeus who had only the evidence of their eyes to guide
them. A shrew is not always a shrew. A mole is not always a mole.

Calcochloris tytonis
and its golden brethren constitute the family
Chrysochloridae
, and were originally described 250 years ago by Linnaeus himself. DNA and fossil evidence suggest that their clade, the order
Afrotheria
, first branched out some 100 million years ago. The world then was unlike anything humans have ever known. Antarctica seems to have been some kind of tropical paradise. Evolution had just produced the first bees, but ants still lay in the future, as did
Tyrannosaurus
, bats, butterflies and, a very long way down the track, humans. The earth itself was heaving with massive uncertainties. Shifting tectonic plates were tearing apart the great lumps of rock that would morph into South America and Africa, and it seems probable that the proto-Afrotherian, whatever it looked like, was isolated on the African side. A million centuries later, we can thank it for the aardvark, the elephant and the eponymous ‘shrew'.

And also, of course, for golden moles. In the 250 years since their discovery, they have proved remarkably difficult to know. Gary Bronner attributes this to the remoteness and smallness of their ranges, and to the typical shyness of small blind creatures that spend their entire lives underground. This rules out casual sightings and makes them extremely difficult to track down. More pertinently perhaps (for we are talking about Africa), the abundance of more charismatic animals has denied them the attention they might have received in a poorer environment such as Britain's. (The truth of that is rubbed in, on this very day of writing, by a new book published in Britain by the Mammal Society on its top priorities for conservation – red squirrel, hare, harvest mouse, hedgehog, wildcat, pine marten and polecat.)

I am afraid that what I have written may sound more definitive than it really is. Taxonomy forever is in flux – written in
sand, not carved in stone, and varying from source to source. What other scientific discipline has been at the same time so meticulous and yet so unreliable? For all their invisibility, golden moles are a good example, being passed like foster children from family to family. It was suggested in 1916 that they should be given an order of their own, but they were dumped instead in
Insectivora
– the order of insect-eaters. But diet is too loose a concept to be genealogically useful. Imagine lumping flesh-eaters together. Your Aunt Agatha would be in the same order as her cat. The whole order of insectivores, little more than a lumber-room for odd mammalian bits and bobs, was later cleared out and its denizens rehoused.

To begin with, the bracketing of golden moles with tenrecs rested on their unpronounceable teeth. When it comes to obfuscatory language, scientists need no lessons from lawyers. In the tiny mouths of golden mole and tenrec we find a real whopper –
zalambdodont
. It is an adjective, and it describes their molars. From the
Complete Oxford
– for it's beyond the scope of any single volume dictionary – I learn that ‘zalambdodont' derives from the Greek words for the letter
lambda
and
tooth
, and that zalambdodont teeth have V-shaped ridges on them.

‘Zalambdotonty', however, turned out to be one of those misleading physical coincidences like the elephant shrew's nose. As Gary Bronner notes, V-ridged teeth have occurred independently in several other mammals (solenodons, for example), so it is probably explained by morphological convergence rather than by common ancestry. In a further twist, this has turned out not to matter. I won't try to describe, or pretend to understand, how genetics confirmed what the teeth had first implied – that golden moles and tenrecs had so much shared history that they were a clade in their own right. But that is what happened. In 1999, therefore, from within the ‘superorder'
Afrotheria
, the new order
Afrosoricida
was born – the exclusive preserve of golden moles, tenrecs and otter shrews, now out on a twig all of their own.

Thanks to a paper by Gary Bronner, I am able to put a bit more meat on the bones. There are, he says, twenty-one known species of golden mole, all confined to sub-Saharan Africa. Despite their name (who could be surprised?), they are not all coloured gold. The family name,
Chrysochloridae
, derives from the Greek, ‘green-gold', a reference to the ‘iridescent sheen of coppery gold, green, purple or bronze' on their fur. This chimes very nicely with the ‘metallic reflections' noted by the
British Cyclopaedia of Natural History
in 1836. The Victorian authors, however, had complained that a stuffed skin could give them ‘no idea of what the living animal is like'. Here Bronner is more helpful. Despite variations in size and colour, they all look very similar. He sends me back to the dictionary to find out what ‘fusiform' means (lozenge-shaped body tapered at both ends), but otherwise his word-picture has a Dürer-like precision. The forelegs are short and powerful with ‘pick-like' claws. There are no external ears, eyes or tail. On the densely furred pelt, the woolly under-fur is protected by a moisture-repellent overlay of ‘guard hairs'. Beneath all this lies a thick tough skin which is particularly robust on the head, and the muzzle has a leathery nosepad to protect the nostrils. Underground the animals tunnel like machines, with upthrusts of their flattened heads and down-thrusts of the claws, leaving a ridged ‘wake' on the surface as they go. A few of them also throw up molehills, thus adding to the confusion with the European
Talpidae.