As every reader will know, plants – whether they live in water or on land – gain their energy from the sun-rays that flood our planet in light. The process by which this light energy is exploited and converted into chemical bonds is invisible even to the strongest microscope. Nonetheless, scientific research has deciphered the process known as “photosynthesis”. Simply stated, the energy quanta of the light rays are harnessed to build up molecules from atoms. The solar energy is converted into chemical bonds. This energy binds oxygen, hydrogen and carbon atoms to form carbohydrate molecules such as starch.

There is no need to go into the chemical cycles involved here. The fact remains that the energy quanta in these molecules are encapsulated in what amounts to tiny “cages”, and this energy can be released whenever the plant needs to fulfill some task. In this case, the molecules are broken down into their building blocks and the cages opened. This released energy can then be used to build up other molecules, giving rise to proteins, fats, or other carbohydrates which, in turn, are used to form stalks, leaves, roots, and other necessary organs. The highly complex, miniature workshops in which photosynthesis takes place are termed plastids and are largely concentrated in those leaves that face the sun. Aquatic plants extract all the matter needed to produce their organs from the surrounding medium; land plants acquire some of this material from the air and the remainder from the water that the roots soak up from the soil. On land, getting enough water is a critical factor. During the day, light is typically available in superfluous amounts. The apparatus needed to harness this light, however, is very “expensive”, and these costs ultimately decide – in the form of competition between plants – which individuals and species prevail. Plant growth and reproduction also entail considerable costs, but these processes need not concern us here. The important thing to note is that all the other molecules formed by the plant – not only starch – also represent energy depots. The atoms they contain are all held together by chemical bonds, i.e. converted solar energy.

Energy acquisition in the animal kingdom, which should interest us because our own bodies use the same mechanisms, is quite different from that of plants yet also shows astounding parallels. Namely, both animals and plants break molecules down into their components in order to release the contained energy. The one significant difference is that animals encapsulate energy in “cages” not of their own making.

Animals therefore rely on biting off  and digesting pieces of plants or other animals – or on devouring their prey whole – in order to use the organically bound energy for their own needs. In this sense, all animals are “predators” based on their diet. Biologists tend to differentiate between “plant-eaters” (herbivores) and flesh-eaters (carnivores), but this creates a false impression. Although plants cannot actively defend themselves, do not flee, and do not emit cries of anguish when they are eaten, they suffer precisely the same fate as an animal prey that is bitten or swallowed whole: in a violent act, they lose parts of their bodies or their very existence. In the case of scavengers, there is no resistance at all, but only because the dead organisms – the carrion – can no longer put up a fight. Here, the violent nature of the act is reflected in the aggressive behavior and bitter fighting with competitors who all want a piece of the same prey⁷.

Competitive behavior between the animals is often considerably more brutal than the predatory act itself. Even if the competitors oftentimes never actually come face-to-face, it still remains a life-and-death act. An animal that fails to acquire the energy it needs for its life processes starves and is eliminated. While this process is not quite so visible in plants, it is not one bit less harsh. A perfect example of this ruthless selection is the many seeds that are widely disseminated by one means or the other: only very few land on “fertile soil” and survive to form a new plant individual. Moreover, the behavior of neighboring plants is much less friendly than the harmonious impression we get when pleasantly strolling through a meadow or forest. Above-ground, leaves and branches fight for the light they require, below-ground the roots compete for crucial water resources. In both animals and plants, so-called monopolists – forms that outcompete all others – are rare. While extreme specialists may qualify, they reproduce so quickly that they soon face stiff competition – namely from members of the same species rather than from individuals of other species.

I emphasize these interrelationships here because they will form the cornerstone of our later deliberations. In this light, the term “evil” is inappropriate for an animal that preys on and thereby damages or kills another animal, or that tears pieces from or devours plants whole. From our human, emotional standpoint, life itself is an exceptionally ruthless and brutal process. Darwin was among the first to clearly point this out. Our inclination to derive pleasure from nature and its many wonders lulls us into forgetting this. Novelists, poets and film producers outcompete each other to present us with a picture of nature that is more fantasy than reality. This book concentrates on animals, and all are unequivocal predators, whether they be traditionally appealing, such as a deer, or an object of fear, such as a rattlesnake⁸. In order to acquire energy, they all must seek and overpower prey. This is equally valid for an elephant and for the parasite that enters and exploits the body of another organism, thereby damaging and often destroying it. Whether the prey be animal or plant is immaterial. The goal is to snatch the energy that others have built up. The fact that this process also yields material – valuable building blocks – is an additional advantage. In plants, energy and material are gained from different sources, whereas both are gained at once in the “predatory” animal strategy. Importantly, animals can go for long times without consuming new building blocks, but they cannot survive a split-second without energy. Most of the consumed material is eventually excreted. In all these processes, whether it be foraging for food, attacking prey, or fighting competitors, one central aspect remains invisible to us. I am referring here to the chemical energy that plants extract from sunlight. When an animal eats that plant or itself falls prey to some animal, this energy is passed on directly from one organism to the other.

What about the highly touted partnerships, mutual support and associations that organisms on this planet exhibit? Are predation and competition not balanced by an array of “friendly”, synergistic acts? While this may be true, it by no means changes the overall picture. The development of symbioses is a case in point, for example the hermit crab that deposits an anemone on its snail shell. The anemones give the crab an additional measure of protection against its enemies, whereas the anemone gets a free ride and can take advantage of better life conditions. Termites would be unable to digest their food, namely wood (i.e. they are unable to open the “energy cages” mentioned above), were it not for the protozoans and bacteria that inhabit their guts. The latter benefit from being effortlessly supplied with sufficient wood to extract energy for themselves. In lichens, algae and fungi are so intimately united that they were long thought to be single organisms. In the wolf pack, one wolf helps the other: in an ant colony, the division of labor is reminiscent of communities established using human intelligence. From another perspective, however, the protection that the anemone affords the hermit crab (thereby allowing it to survive) is a distinct disadvantage to the crab’s prey. For the prey of a wolf pack, the pack itself is a considerably greater threat than any individual wolf. And the same holds true for insect states. Such partnerships spawn ever more efficient predators. The good cooperation between the partners is a prerequisite for enhanced success – the partnership itself, however, simply represents a “higher-order” predator.

Even the sacrifices that brooding parents must make to feed their young – an act we so sympathize with – changes nothing in the overall concept. While those parents certainly help their offspring by protecting, nourishing and nurturing them, they clearly do no service to the prey that those offspring will one day pursue. One species boosts its chances of survival… but to the detriment of individuals of other species, i.e. those that are the preferred diet⁹.

A particularly striking example of how poorly the layperson’s assessment of biology meshes with reality is the little-appreciated fact that plants could not even exist if animals did not eat them. Conversely, the existence of plants is an equally fundamental prerequisite for the existence of animals. Plants need carbon dioxide to fuel photosynthesis, whereby oxygen is excreted as a waste product. Animals, on the other hand, require oxygen to fuel digestion, exhaling carbon dioxide as a waste product. The bottom line is that most animals would ultimately suffocate without plants, and a planet without animals would deprive plants of basic ingredients for photosynthesis. The overall balance between the number of organisms from the animal and plant kingdoms is one of life’s more astounding phenomena.

Ever since the differentiation of these two forms of energy gain, relatively soon after life was created some 4000 million years ago, those two enormous and highly diverse groups functioned as mutually dependent partners. Nine-tenths of evolution took place in water: The first organisms were unicellular plants and animals that adapted to the myriad of opportunities in the seas. Then, about 1800 million year ago, multicellular organisms arose; they were composed of ever greater numbers of individual cells that remained attached to one another rather than separating after cell division, forming increasingly larger colonies and featuring a division of labor (Fig. 3). These multicellular organisms – some being plants, others animals – were initially restricted to aquatic habitats. Only about 400 million years ago did some plant species conquer land, soon to be followed by animals. The continents were soon populated, but the above-mentioned fundamental interdependence of fauna and flora remained. Again, sentimental human interpretations about the struggle for life are misguided. The overall evolutionary process is promoted when an animal consumes a plant or when one animal preys upon another: only the most adept and able individuals and species escape their predators and survive, leaving the most fit to reproduce.
 
 

Fig. 3: The dynamics of the evolutionary process (highly schematic). We now believe that life began in the shallow-water zones soon after the development of the hot ancient seas about 4000 million years ago. Initially, the process involved tiny molecular structures that were capable of replicating. The most suited types survived, enlarging and improving these earliest life-forms, which ultimately yielded the first unicellular organisms. The development of multicellular organisms marked a second highlight. Land was first conquered 400 million years ago, and humans arose about 2 million years ago. More that 90% of the evolutionary process therefore took place underwater. Overall, this development can be likened with a river whose power and volume gradually increases over Earth history. Human technology contributes considerably to its ongoing expansion. Fluctuations in volume are omitted here. (compare Figs 10 and 20). After H. Hass 1985.
(Mensch...human, Landeroberung...hand conquered, Entstehung der Vielzeller...first multicellular organisms, Entstehung der Einzeller...first unicellular organisms, Einsetzen des Lebensprozesses...origin of life, Entstehung der Urmeere...origin of ancient seas, Entstehung des Erdballs...origin of Earth, Millionen Jahre...million years)
 

Understanding this constellation is essential for the further deliberations in this book because it enables us to see things as they are. This second premise should force us to recognize that all animals gain energy in the same principle manner: by acquiring foreign organic structures and exploiting the useful energy they contain. The human body is no different.
 

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