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| Unusual Animals |
The earth, from a purely celestial point of view, is unremarkable. It is a small planet in a solar system orbiting a medium-sized star in a smallish galaxy, the Milky Way, which contains billions of solar systems. Th e Milky Way is but one of billions upon billions of galaxies in the incomprehensible vastness of the universe. Yet, in one respect, the earth is special beyond compare. It is the only place we know of on which there is life. Life is such a small, seemingly insignificant word, yet it encompasses a fantastic diversity of living forms. Th e exact time and nature of life’s appearance on the earth has divided scientists for decades, and it will continue to do so because the time spans with which we are dealing are huge, almost impossible for us to grasp, and the evidence is fragmentary and hard to come by. What we do know is that the earth is very, very old—4.6 billion years old to be exact—but for the vast majority of this time, it was a lifeless globe cooling from the fi res of its creation, circling the sun in the young solar system, while being heavily bombarded by asteroids. Over hundreds of millions of years, the earth changed and the asteroid impacts became less frequent. Oceans formed and our planet became slightly more hospitable, but conditions on this primordial Earth were still very different from the comparatively balmy conditions we enjoy today. And then, more than 3 billion years ago, the first life evolved. Where and how are questions we can only make good educated guesses at, but an experiment conducted in the 1950s by scientists in the United States showed that lightning bolts discharged through an atmosphere, the likes of which could have shrouded the young Earth, could have produced biological molecules—the precursors of the first simple cells. Although these experiments have since been called into question, as more recent findings suggest that the mix of gases used by the scientists to mimic the atmosphere of the young earth was probably inaccurate, they do give us an idea of what may have happened all those millions of years ago. Th e complexity of these first biological molecules increased over the eons, eventually forming the first self-contained biological systems, which in turn gave rise to the fi rst proper cells—the first life.
Th is first life was no more than simple, single-celled organisms, and these organisms had the earth to themselves for a long, long time. In the atmosphere that shrouded the earth at this time, oxygen was as good as absent, but it is thought these fi rst life-forms created oxygen as a waste gas. Over more immense stretches of time, the levels of oxygen in the atmosphere steadily grew until oxygen became quite abundant. Th en, around 700 million years ago, this simple life gave rise to increasingly complex forms. From that point onward, the diversity of life on earth exploded. Lots of diff erent life-forms and body plans appeared, some of which were successful, spawning long, unbroken lines of descent, while others disappeared into prehistory. Th e life-forms interacted with and adapted to each other, becoming ever-more entwined. Th e extraordinary diversity of life on earth today refl ects the relationship between organisms and their environment—an intricate web of interactions with the continual processes of adaptation and change, fine-tuning every species over time to its environment. Life-forms have become so attuned to their environment that scarcely a niche is vacant; in almost every conceivable habitat on earth, animals can be found. In the deepest parts of the ocean, more alien to us than the surface of Mars, creatures thrive. Even in the coldest and highest places on earth, you would be hard pressed not to see some form of animal life. To us, perhaps the most bizarre place to live is inside another animal, yet many creatures have taken to this parasitic way of life and have become very good at it. Traditionally, scientists have classified life on earth into five different kingdoms based primarily on shared characteristics. Th is system has undergone many modifications, but it is straightforward and I use it in this book to describe how animal life is categorized. Th is system of classification is hierarchical, starting with the kindgom level, followed by phylum, class, order, family, genus, and species. Organisms are named by a two-word system, the genus followed by the specific epithet, which together give the species’ scientific name. For example, the European honeybee’s scientific name is Apis (genus) mellifera (specific epithet). In this classification scheme, the fi rst and most primitive kingdom is that of bacteria. Next are the plants, familiar to us as they dominate terrestrial ecosystems. Th e fungi represent the third kingdom. Th e fourth kingdom is the one to which we belong—the animals. Th e fifth kingdom, a sort of taxonomic dustbin, includes the protists, organisms that do not really fi t in to any of the other four kingdoms. Th e topic of this book is the diversity of the animal kingdom, but you will not fi nd an inexhaustible list of all of the animals on earth between the covers of this book—far from it. Such a book would take years to read, and it would hardly be the sort of thing you could easily keep on your bookshelf. No, this is essentially a cherry-picking of the animal kingdom. It only covers living animals because although long extinct animals are fascinating, their lives are the stuff of guesstimate. Bones and impressions of long dead bodies can only tell so much. Th is book is a selection of those animals whose fantastic habits and lives really hammer home the message of how remarkable our planet is. All the animals you will read about are real. Some are found outside your back door; others dwell in habitats where humans rarely venture. Some are miniscule, barely visible to naked eye, and some are massive, thousands of times larger than a fully grown human. Many of them are rarely seen, and there is still a great deal to learn about their lives. Th e scientists who study animals are known as zoologists, and it is these people who unravel the mysteries of the animal kingdom. Scientists, by their very nature, have an urge to categorize and order the things they study, and zoologists are no exception. All animal life may be divided into 38 different categories, or phyla. Each phylum contains animals that in one way or another are very similar, and they may be grouped by shared physical characteristics or genetic
similarities. Animals are continually being shifted within and between these phyla as scientists understand more about DNA and genetics. It has to be remembered that these phyla are a construct of the human mind and are merely an abstraction that allows us to make sense of the natural world. Th e number of species within these phyla is a huge bone of contention. Estimates range from 1.5 million to 100 million, but we may never know the true number. Regardless of the human need to categorize and identify things, it goes without saying that animals are a source of intense interest for a large percentage of the population. Perhaps this stems from the more primitive days of the human race when we lived in much greater harmony with nature. Before the days of agriculture and even civilization, our forebears would not have lasted long without a thorough understanding of the animals that shared their environment— which species they could use for food and which species they should avoid. Today, you can still see this impressive level of understanding in the ways of the tribes that survive in the more remote reaches of our planet. For thousands of years, aboriginal people have lived in the same way thanks to their intimate knowledge of the world about them. Today, most people’s interest in animals begins in childhood with the creatures found in a typical backyard, inevitably, the ones lovingly described as creepy-crawlies—the insects and their relatives. These animals are easy to find and easy to keep in glass jars or old margarine tubs. Th is fascination with bugs grows, and before long, you find yourself reading about other animals, some of which you will probably never see but whose origins, diversity, and astonishing lives amaze you. Th is book is an encapsulation of this path of curiosity, and it draws on things I have read and things I have seen. I hope that whoever reads this will fi nd the animals contained herein as interesting as I do.
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