Dry Storeroom No. 1 (9 page)

So now our specialist has carefully looked through the pages of a couple of dozen monographs and papers, comparing illustrations of many species with the specimen in front of him. Piles of old books and reprints of papers litter the office floor. He is convinced that the species he is looking at has never been seen before, based on his wide experience of “his” organisms. It is a new species. He now needs to give it a technical description, illustrate it accurately, give it a new name and then get it published. He thinks that it is an exceptionally wonderful example of its genus, so he decides on the specific name
mirabilis
(Latin, “wonderful,” “marvellous”). He checks through all the publications before him; sadly, he finds that a Lithuanian Jesuit has already used the epithet
mirabilis
for a species of the same genus in 1896 in an obscure journal published in Vilnius; this species name is therefore unavailable, and he must find another one. Cursing slightly, he reaches for the Latin dictionary and finds
repanda,
“sought after,” instead; good—this one has never been used before, and it will suffice. The next few days are spent in writing an accurate description of the new species, in language as dry as a James Bond martini, with a differential diagnosis saying how it differs from all species known previously. The language is a disguise for the excitement of finding a species new to science, a formal cover-up, or an epistemological stiff upper lip. He might prepare careful drawings under the camera lucida, or supplement his accurate but slightly soulless drawings with photographs prepared by the Museum’s skilful studio photographers.

The new species is almost ready to go to publication, but before it can be a valid addition to biodiversity some other important criteria have to be fulfilled. A specimen from the collection has to be selected as the “type specimen” this is a unique specimen upon which the identity of the new species must ultimately rest. It is known technically as the
holotype
in animal taxonomy, and to be valid must be given an official museum number unique to it. Other specimens in the original collection identified by the author are
paratypes.
Together, these specimens constitute the type collection—the material that provides the material basis for a species’ identity in perpetuity: serious stuff. The type specimens are the scientific treasures behind the scenes of the Natural History Museum, a register of biodiversity, held for future generations. They are the ground truth for species in the natural world. Scientists who wish to know whether they are really dealing with the same species will, in the end, have to refer to the types for a definitive opinion. Is this weed that has suddenly taken over crop fields in South America a European invader? Is this fossil ammonite the same as one described in the early nineteenth century from Dorset—and hence are the rocks from which it came likely to be the same age? Is this fly that is plaguing cattle in Namibia the same as one from Libya, and if so how did it get there? Ultimately, the resolution of such questions means that the original specimens have to be examined. Once again, the web is making some difference to how this works out in practice, since it is possible to visit collections in virtual reality. But many fine details—like tiny hairs and microscopic characters—will probably never be accessible over the web. Then there are the sheer numbers involved. A recent estimate puts the London museums’ holdings of types at about 670,000; it would be a vast undertaking to put them all online. Originally, the Natural History Museum hung on to its types as firmly as the original BM hangs on to the Elgin Marbles. But now, in more enlightened times, type specimens can travel to recognized sister institutions and bona fide workers. And of course the latter are always welcome as visitors to the vaults. This process probably helps more than anything else in recognizing synonyms, and improving the global standard of taxonomy. So the spoils of Empire have now become a global resource, one that should be recognized by all international bodies concerned with biodiversity.

Scientists deposit their type specimens in the Natural History Museum, or its equivalents elsewhere in the world, because they know that the specimens have been properly curated and cared for there, and should be looked after for future generations. Hence the collection builds steadily in importance as a reference base. There are plenty of examples elsewhere where type specimens have not been recognized for what they were. There are universities that have supported a well-known scholar, and when he or she dies the collections made by the scientist have been assigned to a dusty corner and forgotten. I know of an example where type specimens of fossil ammonites have been rescued from a skip; they might have finished up in the foundations of a building rather than as the foundation of a species. Some type specimens are historically celebrated. The duck-billed platypus (
Ornithorhynchos
) is a bizarre Australian mammal which is famous for laying eggs and having mouthparts like a shoveller duck, not to mention a tail like a beaver. When a specimen was brought to Europe in 1798, it was thought to be a fake, a confection stitched together from different animals by a taxidermist with a perverse or mischievous sense of humour, for it was an animal that should by rights not exist in a well-ordered world. A careful description of the type material proved that the antipodean puzzle really was what it purported to be. We are now quite familiar with its living reality thanks to wildlife photography of the platypus in its natural habitat, where it uses that curious bill to sense small animals on stream bottoms, and the tail to help it swim—not so much an unnatural impossibility as a highly evolved specialist that retains some ancient characteristics. But the type specimen still resides in the collections of the Natural History Museum as a slightly scruffy skin, a veteran of the triumph of science over disbelief. Most types are altogether less famous, and much less conspicuous. Holotypes in the Palaeontology Department are marked only by a modest green spot attached to the rock. Their presence is known only to a small number of specialists and curators. But their importance will not diminish as long as our species pays any attention at all to fellow inhabitants of our planet. The types are still only a small part of the collections; the rest includes comparative material of many more species, or collections made from inaccessible parts of the world, or collections associated with a distinguished individual; so many riches contribute to the archive of the natural world.

The type specimen of the duck-billed platypus (
Ornithorhynchus anatinus
). This animal was not believed to be real when it was first described.

The taxonomic process as I have described it would certainly have applied at the time I first nosed my way cautiously around the maze of offices and corridors in the Natural History Museum. I still believe today in the primacy of collections and specimens—they don’t go out of fashion, because they are preserved to outlive any passing phase of epistemology. However, it would be surprising if there had
not
been changes in scientific practice and theory over the last decades, if only because science always moves on. I deliberately concentrated on species above, because that basic unit has retained its central role in systematics, no matter how technique and theory have changed elsewhere. Species are not merely specious.

The most important change in the scientific firmament was the appearance of molecular techniques. The possibility of sequencing genes followed upon the unravelling of the structure of DNA—and now has reached new heights after the decoding of entire genomes, including that of our own species. What began as a major technical challenge is now almost entirely routine, and every research institute worth its salt, including the Natural History Museum, has a molecular biology laboratory, staffed by scientists of the white-coated variety, slaving away with test tubes in front of highly sterile machines. Nowadays, an organism must reveal its secrets down to the molecules in its DNA or RNA. Gene sequences provide a whole plethora of characters to add to the traditional morphology—something to challenge the hairs on legs, spines on shells, pattern of bones or structure of flowers. Because the genome is almost unimaginably huge, the potential for information locked in its sequences of bases is theoretically almost endless. It is small wonder that there has been a boom in the employment of molecular biologists at the expense of traditional experts on groups of organisms.

More than twenty years on from the appearance of these techniques it is possible to see just how many questions can now be tackled which were previously beyond reach. Many people have used the obvious pun “designer genes” before, but it is not a bad phrase to summarize what scientists actually do with the vastness of the genome. They use different parts of it for different purposes. If they have been curated appropriately, pieces of type specimens can even be fed into the DNA factory, thanks to a technique known as PCR that “magnifies” sequence information from tiny pieces of tissue. There is, of course, much variation in the genome within a species. Some variation is at the level of the individual—hence the possibility of “nailing” a criminal for an offence using stored samples such as blood or semen years after a deed has been committed. The gene sequences in question identify a particular person beyond doubt, like a fingerprint. Other changes in gene sequences are conserved for slightly longer periods of time; sections of DNA called microsatellites have high rates of mutation, which makes them ideal for studies within the historical time span and within species—for example, in tracing movements of human populations around the world. Other parts of the genome change still more slowly, and yield sequences that are of particular use in recognizing species—we will come back to these again, because they are of special importance in taxonomy. Other parts of the genome are generally conserved, which means they accumulate changes only very slowly, over millions of years, or even longer. Some of these genes are important in the functioning of any organism—they include genes that encode proteins, for example. Or there is the RNA of the cell’s “powerhouse” organelle, the mitochondrion, which was one of the first molecules of this kind to be completely sequenced. Such slowly changing genes and sequences allow the scientist to “see” backwards in time to the divergence of major lines of evolution, to examine relationships between different groups of organisms that might previously have been investigated only by the palaeontologist delving deep in the fossil record. To say that these discoveries had a profound effect on systematics would be a considerable understatement: they provided a whole new way of looking at the natural world. There are even genes that could potentially “see” the separation of the major designs of animals and plants hundreds—even thousands—of millions of years ago. In 1991 great surprise greeted the discovery that the sequence of the elongation factor gene in the nematode worm
Coenorhabditis elegans
was more than 80 per cent similar to that in a mammal; here was common ancestry writ large. Some genes were evidently so deep-seated that they continued to do their work over a timescale of many, many millions of years. Such evidence proved beyond question that we are one with the worm and the bacterium.

The small nematode worm
Coenorhabditis elegans
—so important in working out the genetics of all animals