The decades before Darwin’s Origin were rich in hypotheses and speculations regarding diversity and classification and rich in new zoological material from expeditions. Zoos, collections and popular books increased public awareness of nature’s diversity. Cuvier followed Buffon in claiming that to classify animal diversity, we must know all features, not just external ones. To classify animals that fit one group by one trait and another group by another, he outlined his Principle of Character Subordination: the more significant a functional organ is, the more it should weigh in classification. Accordingly, he distinguished animals from plants by the presence of a nervous system, and within animals, four major branches by nervous system complexity. He expanded the Linnaean taxonomic hierarchy by establishing additional optional ranks (Branch, Section, Tribe and Subgenus). He viewed organisms as integrated wholes, whose organs function in harmony; consequently, no organ can change without impairing this functional integration. Cuvier used this Correlation of Parts to predict the structure of complete animals from a few remaining fossils. He rejected theories of animals forming a single Great Ladder of Life, with a rising order of complexity. Cuvier created and established modern Palaeontology by presenting extinction as a natural, global process. By proving that mammoths differed from elephants, he rejected Buffon’s theory of the Earth gradually cooling down and of animals migrating from slowly cooling poles to the warm tropics. He identified an extinct giant sloth, an extinct giant deer and an extinct tapir, evidence of once giant creatures that no longer exist. Reptiles came into existence before mammals and were once the dominant fauna and there were flying fossil and swimming ones. From proving that a fossil with a skull and teeth of a marsupial must also have other marsupial bones, Cuvier formulated the Principle of Correlation between Organs. As all organs of every animal function together harmoniously and are interdependent, and the existence of a species depends on the manner in which these organs interact, no organ can change without the other organs also changing. Hence, species cannot change; as fixed entities from their moment of creation, they are so well adapted that only catastrophic events could exterminate them. Cuvier suggested a series of sudden disastrous catastrophes that hit Earth, destroying many animals. New fossil forms appear abruptly after each catastrophe and persist unchanged until their sudden extinction by the next catastrophe. Lamarck believed in a Principle of Life that drives life towards ever-greater perfection. Animals and plants form two series of increasing perfection. Plants synthesize simple compounds that animals assimilate to create complex compounds. The Principle of Life expresses itself as the movement of fluids within the plant, as determined by the environment. In animals, the movement of fluids is by internal forces. Lamarck rejected the claim of extinction as a natural process, with previous animals going extinct by massive catastrophes, as Cuvier had suggested. He claimed that nature changes gradually, constantly balancing itself, so no species is ever lost. Earth’s climate has changed very slowly, and so too have plants and animals. Many seemingly fossil forms actually live today, slightly changed but still closely resembling the fossil. Ammonites and belemnites are still alive in unexplored deep seas. Marine fossils occur on mountaintops because of a slow, continuous westward movement of the Atlantic Ocean basin over Earth’s surface, the sea ceaselessly eroding eastern coasts and abandoning western ones. This displacement has left fossil marine shells far from the sea. Lamarck at first believed that animals formed a single Ladder of Life, of increasing complexity. Classes, Orders and Genera interlink via interim animals, as Lamarck’s (remarkably poor) mollusc classification demonstrated. Nature began (and begins) by spontaneously creating simple animals from molecules that spontaneously assemble to form infusoria, which proceed to form some major groups. Intestinal worms also appear spontaneously and proceed to form other ones. The Principle of Life builds nervous system complexity, with animals lacking nerves being insensitive; animals with simple nervous systems following instincts; and intelligent animals following ideas. Adaptive change also determines structure. Amphibious worms adaptively diversify into air-breathing amphibious insects, which change to terrestrial insects that become arachnids, which change into crustaceans. Other worms become annelids, barnacles and molluscs. In originally amphibious mammals, plant browsers became terrestrial herbivores, flesh-eaters became terrestrial carnivores, and aquatic dwellers became whales. Species-level diversity, in response to environmental diversity, involves only external features. Species changing habits change shape and convert into new species as lateral ramifications from the linear ladder. Use inherently strengthens and enlarges organs; disuse weakens them to disappearance, so inheritance of acquired characters creates animal diversity, in contrast to theories of unchanging species that perish during catastrophes. Geoffroy suggested that all animals of a group share the same basic set of organs, which never change their relative locations. Animals, during embryonic life, go through phases recalling their ancestors, and this, with vestigial organs, indicates the derivation of animals from a common archetype; hence, species transform over time. He erroneously extended the vertebrate archetype to include insects as vertebrates that live inside their vertebrae and walk on their ribs with their bellies facing upwards and later claimed that molluscs also share this archetype. He thus unified all bilateral animal groups under one basic plan, thereby suggesting to reject Cuvier’s theory of four animal branches. Goethe suggested that vertebrates have basic units that repeat themselves throughout the body. This calls for an ideal vertebrate, from which diversity develops by modifications of such units. Others believed that each such segment is a zoonite, a miniature animal. Zoonites are identical throughout the animal kingdom, the animals they form differing in number and grouping ways. Animals thus consist of multiple organisms that were once capable of living independently; gradually, they coalesced and modified to conform to the functions of the body, thus resembling a civilized human society evolving from a savage one. Blainville classified biodiversity by external, sensing features that enable movement. The more an animal feels and moves, the higher its place on the Ladder of Life. Forming a strange classification that linked vertebrates to arthropods and molluscs to arthropods, he rejected Cuvier’s four branches: animals form a single Ladder. Oken suggested five main steps of animal progress: invertebrates, fish, reptiles, birds and mammals, corresponding to the five senses of touch, taste, smell, hearing and sight. Animals reach higher steps on the Ladder by adding senses; as no senses are ever lost, organs in primitive groups may become different organs in advanced ones: bivalve valves become bird wings. The skull consists of modified vertebrae; jaws correspond to arms and feet and teeth to claws or nails. Plants, animals and man first formed from a primitive slime by unicellular organisms agglomerating into multicellular organisms. Semen consists of single-celled creatures and generation repeats that primitive, slime-formed creation. In developing from a fertilized egg to an adult, animals pass through stages representing the groups below them. The joint manifestation of nutrition, digestion and respiration is self-movement. Some authors strictly divided each vertebrate class into five series, each with precisely three orders. This, too, resulted in erroneous classifications. Humboldt travelled extensively in Spain’s realms in the Americas. He viewed nature holistically , and the unity of nature meant for him the interrelation of all physical sciences . Life is a web of interactions, and the conjoining between biology, meteorology and geology determines where specific plants shall grow. Altitude determines where plants on mountains live and also determines temperature and humidity. Furthermore, vertical plant stratifications reflect global vegetation patterns. Elevation gradients compress life zones that, near sea level, are thousands of kilometres apart. Mountains, by lumping contrasting climates onto a single slope, host more diverse life than other terrestrial systems. By interconnecting climate, geography and nature, Humboldt laid the foundation of plant geography . He also introduced the isotherm, a line connecting points on a map that receive equal quantities of heat. The geographical distribution of temperatures on Earth correlates with the geographical distribution of life on Earth, so he drew curves of equal mean temperatures over the globe, thereby devising means of comparing climatic conditions of various countries. Humboldt collaborated to produce the first comprehensive physical world atlas. It included maps of plant distributions in both latitudinal and altitudinal perspectives. In the early 1800s, the leading embryological concept was that ontogeny recapitulates phylogeny, with stages of embryogenesis mirroring steps of the Ladder of Life, a single Ladder and a single unified body type. Baer challenged this concept. He distinguished four types of embryonic development, corresponding to Cuvier’s four Branches. Embryogenesis advances from the centre to the periphery (Radiata); creates identical forms along a longitudinal axis (Articulata); spirals around a conic space (Mollusca); or forms identical organs along the sides of an axis (Vertebrata). These distinct embryonic types reject the existence of a single Ladder. Early embryos of all animals are similar, but changes accumulate as development proceeds and diverge towards four specific adult forms. General features of a large animal group (a Class) appear earlier in the embryo than specific characteristics (a Genus). Accordingly, Baer classified the vertebrates (with emphasis on mammals) by extensive use of embryonic structures: allantois, umbilical cord and yolk sac. Other zoologists followed Baer and proposed a classification based upon the vitelline sources and from which sides they entered the embryo. By now, scientists had begun abandoning the preformation doctrine; this enabled them to accept animal change through time, as did Baer. New studies of small, low organisms demonstrated their highly complex organ systems and their diversity and that infusorians do not appear spontaneously. This, consequently, rejected theories of a Ladder of Life, of spontaneous creation and of low organisms transforming into highly organized creatures. A new classification based on the nervous system: vertebrates with a spinal cord versus invertebrates with ganglionate nerves. Vertebrates subdivide into those that care for their young (mammals, birds) versus those that do not. Invertebrates split into those with a heart versus those without. The former split into arthropods, with similar ganglia throughout their bodies, versus molluscs with different types. Within Cuvier’s Radiata, the anatomy of starfish and sea urchins differs entirely from that of medusas, corals and sea anemones. The newly established cell theory, that the cell is the basic unit of the living body, inspired studies of the single-celled creatures. Scientists now considered these creatures as consisting an entirely separate Kingdom, the Protozoa, with no digestive, vascular or secretion systems, no muscle or nervous tissue and no egg laying. It consists of five Classes. Gradually, the classification of animal diversity became close to that of today, as regards the major groups. Some naturalists arranged biodiversity in circles, not ladders. Essential to this method were homologies leading from one form to the next, connections linking each member of one series to the corresponding member of another and the homologue series being circular. Consequently, each series must have the same number of members, which happens to be five. Each member in a major circle consists of five minor sub-circles. Biodiversity thus falls into circles within and next to circles, each with five members. Each member of a five has typical features. The first, typical member has the most complete, general features. The second, sub-typical member consists of powerfully armed, destructive animals that subsist on prey. The third is aquatic, bulky and partakes in destructive deeds of the sub-typical. The fourth feeds by suction, has a small head and a weak body, lacks offensive protection and (often) is a parasite. The fifth comprises domestic animals; gentle and familiar with man, they have strong limbs and many head ornaments. Many naturalists experimented with this “Quinarian” classification. Its strictly regular structure was, however, irreconcilable with the idea of change in form over time, following environmental changes. Change would break down this neat five-in-a-circle design into irregular patterns. Environmental pressures may modify pre-existing structures but cannot give rise to new ones; species do not change into other species, and all major groups have always been present. Closely similar environmental conditions scattered over the globe may harbour different species, and this is so because of separate creation events: God had created each species separately in a given area. Slight but continuously changing environments might cause considerable changes in animal distributions, with species going locally extinct and others invading and replacing the annihilated groups. Competition, migration, food shortage, climatic changes or high population densities may also change distribution, and even minor-scale invasions might influence an entire local fauna. Man also changes the environment by transforming natural habitats into agricultural regions. The world’s birds and mammals fall into six major regions that are separate centres of creation: Australian, Neotropical, Ethiopian, Oriental, Nearctic and Palaearctic. Submerged land bridges and continents may account for populations of terrestrial species now separated by barriers of water. Paley suggested that animal adaptations bear evidence of God’s design. There is no order without someone making order, no means towards a purpose without someone thinking of the purpose. Only a wise, all-potent entity can cause this miracle of animal structure corresponding to function. Animal design calls for a designer; the designer is God, and animal adaptations are evidence of His skilful design. Adaptations occur in all creatures and all organs, with some being prepared for future function (milk teeth). Thanks to God’s goodness in creating adaptations, nature is full of happiness and harmony. Evidence rejects claims of organs changing by over- or underuse, of environments determining shape or of animals having achieved their shape by gradual evolution. Evidence also rejects claims that creatures achieve adaptations by constraints during embryogenesis, the shaping of one organ linking to that of another. Over a broad taxonomic front, homologous organs occur—God shows His greatness in that He purposefully constrains His power to a small number of well-defined types. All the endless adaptive aspects of nature point to the existence of God. This argument assumes an analogy between nature and human contrivance: since the latter involves intelligence and purpose, so must the former. Robert Chambers, in his Vestiges, sketched an evolutionary history of life. Fossils progress over time, from simple to complex animals, mostly within existing classes but some as inter-class creatures. Environment and life advance side by side, with life going extinct when environments change. The unity beneath diversity suggests one creation event of potentiality, but potential animals did not all appear at one time. During embryonic development, chemical-electric operations produce cells that may remain as animalcules or start foetal development. Monstrosities might result in transitions from one class to another. There is thus a threefold parallelism: the order of appearance of animals in the fossil record mirrors the order of appearance of their morphological novelties and the order of embryonic development. Harmonious adaptations prove that design presides in all forms of animal life. Similar forms of life occur on stars because matter everywhere is the same; those elements of matter that build animals occur throughout the universe, as do electricity, gravitation and light, all involved in life’s basic procedures and enabling Life to rise spontaneously. Where there is light, there will be eyes, and these, in the stars, will be the same as on Earth. Star inhabitants, therefore, resemble us.