by Jutta Muth and Udo Pollmer

European Institute of Food and Nutrition Sciences e.V., D-27404 Gyhum, Am Kiebitzberg 10
(Based on a publication by JM & UP: Der Mensch - ein Coctivor. EU.L.E.n-Spiegel 2007, Issue 3-4, pp 5-13)
Der Mensch – ein Coctivor (177.77 KB)

Correspondence: Udo Pollmer, Scientific Director of the European Institute of Food and Nutrition Sciences e.V., 
Current Address: D-86456 Gablingen, Achsheimer Str. 6a, Upollmer(at)aol.com

Keywords: human evolution, coctivor, brain, digestive tract, food processing, fire

Summary

Due to the anatomic features of dentition and gastrointestinal tract, humans are coctivors compared to great apes. They depend on prepared, easily digestible food. High energy output from food at low digestion rate has only become possible by using fire and, later on, developing kitchen technology. It has generated resources to...

...enlarge the human brain quickly. Insofar, the place to cook has played a key role in human evolution. However, during the development of modern civilisation, humans have adapted their food to the physiological conditions of their digestion. In view of the enormous importance of manipulated food from breeding to processing, investigations into the presence of such behaviour patterns also in the animal world have suggested themselves. It has appeared that animals generally apply many techniques, too; however, without being able to profit from the enormous benefit of cooking.

1 Introduction

How do we actually know which food, which vitamins, which trace elements humans need? Every self-respecting nation funds institutions, whose job it is to tell the people what they should eat. The result: when it comes to food, every country is brewing its own soup. However, recommendations vary not only from country to country, but also from time to time. While meat was once considered a "piece of vitality", one could never get enough meat, this changed in the 1990s. Instead of a marten's digestive tract, nowadays humans would need beaks, crop and gizzard to peck, pre-soak and grind the many healthy grains. Today, we would need a rumen, in order to benefit from the many types of "vegetarian straw".

2 Looking the anatomy in the face

In this context, it makes sense to study the nutritional requirements of Homo sapiens on the basis of comparative anatomy. After all, people are always talking about a "natural diet", bringing forward that our apes, as they are our relatives, are wise enough to eat only natural raw food. It isn’t uncommon, you often hear in public debate the reference to the supposed vegetarian lifestyle of the great apes. But it is no coincidence that mankind thrives on both, predominantly animal based and vegetable diet. Faced with the choice, they usually combine both in their menu. Man's digestive tract corresponds to that of other omnivores and, of course, to that of his closest relatives, the great apes.

The structural design is the same in all higher primates (HILL, 1958). Nevertheless, there are decisive differences that assign humans a special status. Looking at the human face reveals the first essential difference: humans lack the prognathous snout with large U-shaped rows of teeth, massive chewing muscles and a jaw with strong leverage. A chimpanzee is capable to dismember a captured animal, for instance a forest antelope, with its dentition alone. While P. troglodytes has a scissor-like set of teeth with shovel-like incisors (for fruit), large fangs (wild prey) and strong grinding teeth (seeds and leaves), humans have to do with teeth that are not suitable for shovelling, tearing or grinding. Our dentition is also not suitable for cracking nuts, shells and bones. The rounded dental arches serve only for chewing (Fig. 1).

 

Fig. 1: Robust dentition with Crista sagittalis as a fixing point of strong masticatory muscle (left). Large Neuro-cranium; masticatory muscles are sidewise attached to skull; reduction of teeth and jaw (right).

The indispensable decomposing work has been "outsourced" and since then done outside the body. We humans use tools to cut up a hunted wild boar, strip off the skin, remove the bones, let it hang until its meat becomes tender, pickle the ham in the kitchen so that it becomes even more tender, heat it intensively and finally cut the cooked meat into small pieces. Now it is cut into small bites with a knife and fork. We grind the beef for our meatballs or we cut it to make sausages with a soft consistency. If it's too hard, we grind, ferment, cook or bake it. We like to chew a crust of bread, but we don't use our teeth to grind significant amounts of raw grain or nutrient-poor leaves.

According to STEDMAN et al. (2004), humans owe the regression of their chewing muscles to a special gene mutation (MYH16). This is considered to be as a prerequisite for the growth of the brain. Only when the robust attachment points for the powerful masticatory muscles became superfluous, the skull geometry could change (CURRIE, 2004). The masticatory muscles of the great apes often attach to the crista sagittalis, a continuous bony prominence on the skull, and require wide zygomatic bones to provide space for the muscles. As for man's ancestors, Homo habilis already lacks the crest, the chewing muscles attach laterally, and the neurocranium begins to bulge significantly. Its brain volume of 700 cm³ is almost twice as large as that of the chimpanzee (LEWIN, 1992). Even though the dentition now gradually recedes, it remains relatively robust up to and including Neanderthal times, even though the teeth become smaller and smaller. The graceful dentition is solely typical of Homo sapiens sapiens.

3 The intestine: insights and prospects

These differences between humans and other primates can also be observed in the digestive tract. For example, gorillas and probably chimpanzees as well, are able to digest bones to a certain extent (FOSSEY, 1989). The same applies to many plant fibres (MILTON and DEMMENT, 1988). In contrast, humans must detach meat from the skeleton and peel plant foods before consumption. The higher efficiency of apes in digesting hard-to-digest food comes as little surprise: after all, their digestive tract occupies a significantly higher proportion of body mass than in humans (CHIVERS and HLADIK, 1980). According to GIBBONS (1998), the human gastrointestinal tract reaches 60 percent of the volume of a primate of the same size (Fig. 2). The human gastrointestinal tract - apart from the stomach - is shaped differently. Unusually, its small intestine accounts for 50 per cent of the volume of its digestive tract (Fig. 3). In the great apes, it is only 20 per cent. Thanks to its large surface, which reaches the size of a basketball court (approx. 400 square metres) due to small protrusions (microvilli), the human small intestine quickly absorbs large amounts of nutrients. Neither in the stomach, nor in the small intestine exist suitable microorganisms, which could help to unlock the food.

 

Fig. 2: Brain volume (top). The size of the gastrointestinal tract in humans is reduced by 40% in relation to primates (bottom).

Consequently, humans have adapted to easily digestible, rapidly absorbable food, which can be eaten at any time effortlessly and provides energy quickly. Consequently, so-called "fast food" should enjoy a certain degree of popularity among H. sapiens.

And what about the universally invoked dietary fibre consumption? In many herbivorous mammals, caecum (appendix) and colon (large intestine) are responsible for this. In here these are degraded by the intestinal flora into short-chain, energy-rich fatty acids. However, humans do not have a suitable appendix, and their colon is also quite insignificant as a fermentation chamber. It makes up less than a fifth of the entire digestive tract. In the great apes, the proportions are almost reversed (Fig. 3). It means that our short colon is an indication of adaptation to a low-fiber diet.

Morphological changes are commonly thought to be a long evolutionary process (MILTON, 1999b). But in this case, it is rather the other way round, because the intestinal structure of a newborn resembles that of an adult (STEVENS and HUME, 2004). It is designed to quickly and effectively absorb the infant's only source of nutrition, breast milk, which is high in sugar, fat and protein. As the intestine matures, it is sufficient to enlarge the colon a little more. The gastrointestinal tract of the adult H. sapiens is thus neither reinvention nor degeneration, but simply the extensive retention of something that already existed. The adaptation was supported by the availability of cooked mushy food. This allows infants to be weaned earlier. As a result, the intervals between getting children can be shorter and the number of children per woman increases (WRANGHAM and CONKLIN-BRITAIN, 2003).

 

Fig. 3. Relative volume of human gastrointestinal tract in relation to that of other primates according to MILTON (1999a)

Although humans are omnivores, that does not mean that they eat everything that comes in front of their mouths. In the whole world there aren’t any cultures known that feed exclusively on raw food. H. sapiens is not an ape that has descended from the trees and has to painstakingly learn to search in supermarkets for natural tree bark from eco-rainforests, in order to stay fit. On the contrary, the human digestive tract is just adapted to the processed food that mankind consumed with the greatest pleasure since time immemorial. His digestive tract is smaller because he has transferred this work to the outside - to the kitchen. Man is a coctivore.¹

¹From Latin coquere, to cook, bake, prepare; also coquus, cook. The German word "Koch" is derived from it, just like the English "to cook" and the French "cuire".
The word "cookivor", however, which is occasionally used in English, is misleading. Based on the Latin origin, it would mean the consumption of the cook.

4 Elective affinities

The best anatomical match to the human digestive tract is not found in the great apes, but in the capuchin monkeys (Cebus capucinus). Both capuchin monkeys and humans have a long small intestine and a short large intestine (MILTON, 1987). The capuchin monkey is also an omnivore: it catches insects, spiders and birds, but is equally fond of sweet fruits, eggs, corn and fat-rich seeds. It has a relatively large brain and is considered intelligent.

But why can't humans live on spiders and sparrows, corn and medlars just like their digestive relatives? In moderate latitudes, the "small stuff", difficult to collect, would provide sufficient food energy at best in late summer. That's why survival trainers prefer to go through the woods and meadows in August or September, picking berries and mushrooms or catching small game. In winter, only hunting can secure the caloric supply, which required tools and fire. Without these tools, neither the hunting of a deer nor the consumption of small animals would be possible, because humans, unlike apes, cannot break them down with their teeth and cannot digest fur or bones. In the Arctic Circle, where the growing season is extremely short, humans had no choice and need to specialise in fatty meats such as seal blubber.

The situation is different in the tropics, where socially living insects such as termites are available all year round and can be collected or harvested with relatively little effort. Not without reason do insects or fat grubs (which are rewarding and easy hunting prey simply because of their size) play an important role as food in the tropics. Chimpanzees also spend many hours a day, picking the coveted little animals with twigs out of their burrows. They could certainly spend the same amount of time gathering fruit or chewing leaves, but obviously the protein-rich insect diet is more important to them. Side note: This suggests - that the advent of man did not take place in the tropics, but in temperate latitudes.

5 Brainfood

Humans need easily absorbed high-calorie food to supply their brains, which consume more energy than the brains of other primates. Its requirement is estimated at about 25 per cent of the basal metabolic rate. The brain of newborns requires as much as 60 per cent of the energy supplied by breast milk (CUNNANE and CRAWFORD, 2003). The energy consumption of brain tissue (in relation to weight) is about 16 times higher than that of muscle tissue (LEONARD et al., 2007). However, energy is not only needed for thinking, but also for heating. Practically, all important organs are protected from temperature fluctuations in the body cavity - the fact that humans have not lost their hair on the head also protects against heat losses.

The fact is that the human brain consumes about three times more calories than that of a chimpanzee (LEONARD et al., 2003). At the same time, primate brains are already considerably larger than those of most other mammals. On the other hand, humans at rest do not consume more energy than a mammal of comparable size (LEONARD et al., 2007). Therefor the calories for the brain are saved elsewhere, namely by relieving the gastrointestinal tract. In monkeys, the correlation between easily digestible food and brain development was confirmed: the higher the percentage of insects and bird eggs in the diet, the larger the brain. A study on 28 different primate species showed that, with increasing consumption of foliage and fruits, the intestine becomes larger and the brain smaller (GIBBONS, 2007).

While an easily digestible diet, low in dietary fibre, is only available in nature in very limited amount, H. sapiens had no choice but to process his food. In doing so, he pursued three goals: Increasing the content of easily digestible nutrients, reducing the fibre content and detoxifying secondary plant substances (antinutrients). The digestion of starch by heat, for example, made it unnecessary to excrete large amounts of starch-cleaving enzymes with the saliva, as is the case with pigs. In this way, our body saves both digestive energy and a constant genetic adaptation to the variable defence tricks of plants. Either a creature adapts to its food or it looks for ways to relieve its digestive tract. Humans have "opted" for the latter in their evolution and have been successful in doing so.

6 Agribusiness and human evolution

However, the development was not limited to the modified digestive tract. In a further step, humans began to adapt their environment, i.e. their food sources, to their digestive tract. Only the deliberate cultivation of food plants and the keeping of livestock, which converts plants that are indigestible for humans or otherwise inedible into animal protein, made it possible to obtain more food from a given area, than was possible for hunter-gatherer peoples. The population density of so-called natural societies is about one person per square kilometre; in Tokyo far more than 10,000 people live in the same area. The existence of cities has always required the targeted production of large quantities of food. Breeding offered a way to improve the food supply.

The driving force behind selection and improving the wild plants is probably to be found in the digestibility of individual varieties. Almost all parts of plants - except fruits or seeds in hard shells spread by mammals - contain defence substances to prevent them from being eaten. But there are always mutants missing those particularly unpleasant antinutrients. For example, acorns used to be an important basic food. For this purpose, they were debittered. However, e.g. among the oaks exist individuals - albeit rare - whose seeds have a significantly lower tannin content. These "sweet acorns" were cultivated (BOLLE, 1891). The same applies to the naked oat, whose grains detach themselves from the sharp husks of the inflorescence. Or the sweet almond, which is practically free of hydrogen cyanide and therefore, with the help of humans turned into the most common almond variety on earth (SÁNCHEZ-PÉREZ et al., 2008).

 

Procedure	Humans	Animals
Breeding	All important food crops and farm animals are the result of long cultivation	Animals as distributors of seeds and fruits; selection of fungal species for cultivation; breeding of new aphid species
Cultivation	Monocultures to increase yields; use of fertiliser and plant protection	Monocultures (fungi) of ants, termites and beetles; use of fertilisers and antibiotics
Livestock	Livestock converts unusable plant material into animal protein	Mass farming of aphids by ants; protection from predators, maintenance of grazing areas
Hunting	Catching fish with nets and bait; hunting wild animals with weapons	Catching prey with nets and bait; hunting small mammals with wooden spears
Mechanical processing	Almost all food is mechanically processed to remove indigestible matter and to facilitate chewing and digestion.	Nuts, shells and eggs are opened with stones; gastroliths grind food in the stomach; food is washed
Fermentation	Cereals (bread, beer), soya, millet, manioc, lactic acid fermentation	Preferably in the body of the animal (rumen, rectal fermentation); Caecotrophy
Detoxification	Breeding, heating, fermentation, geophagy	Soaking of branches; impaling of insects; geophagy
Heating	Obligatory cooking	Occasional use of bushfires for killing and barbecuing prey

Tab. 1. Production and processing of food by humans and animals

The carrot (Daucus carota) is a good example how far our present-day foodplants have moved away from their wild forms and thus offer a new food basis: Its storage organ, which is in its original form characterised by a thin whitish and woody taproot, has been enlarged by breeding to become a turnip. As wild plant, it is sufficiently protected against harmful organisms, otherwise it would no longer exist. To enable us to eat them - and even raw - the content of undesirable antinutrients was reduced through breeding. Since then, they depended on our protection. If cultivated carrots are left to themselves, they soon disappear from their habitat. But man was not only interested in compatibility. At the same time, he tried to increase the yield of calories. For cultivation is only economical if it provides more calories than are needed for production and digestion (Tab. 1).

Societies, without appropriate plant protection techniques, therefore leave poisonous plants in the fields as emergency rations for times of shortage. They are only detoxified after harvesting, like manioc or the Andean potato. As Euphorbia- and nightshade plants, they yield abundant hydrogen cyanide and toxic alkaloids. The cyanide is removed by rubbing, squeezing, fermenting and heating, while the alkaloids, which are heat stable, are traditionally detoxified by leaching and geophagy, i.e. the consumption of special clays. They bind the alkaloids in the digestive tract (JOHNS, 1990; WESTBY, 2002). Only the modern deep-fat fryer made it possible to detoxify the potato practically completely, and its popularity grew accordingly (RYTEL et al., 2005).

Breeding crops is always a balancing act. If too many toxins are removed, the risk of yield losses due to diseases and pests increases. If you increase resistance, the repellents can become dangerous to humans. In the case of potatoes, new varieties had to be withdrawn from the market for this reason (HELLENÄS et al., 1995). The more plant protection techniques are available, the easier it is to do without the plant's own defences. Artificial pesticides (also called secondary pesticides) replace the usually much more toxic natural pesticides (primary pesticides) of the plants. Without plant protection, there can be no high-yield monocultures. In order to secure his supply of high-quality protein, man began to breed livestock in such way, that the animals produce as much "food" as possible with as little feed.

Ruminants such as cattle, sheep, goats and other herbivorous farm animals were initially kept because they convert plant food which is hard to digest for humans, such as grass, leaves or waste food, into meat and milk, but into wool as well. Pigs, on the other hand, proved to be both fertile and unpretentious omnivores and thus profitable waste disposers.

7 Farming practices in the animal world

What at first glance appears to be a unique human achievement, has unexpected counterparts in the animal world. It is true, of course: animals have neither seed multinationals nor genetic engineering laboratories. And yet they also breed plants of all kinds. On the one hand, while they eat fruits and thus spread their seeds. In return, they receive the fruit flesh as a reward. Logically, the different animal species mainly feed on those fruits which are more nutritious and digestible for them. Animals, just like humans, select the seeds that are suitable for them. This results in an effective selection of plants by their respective propagators. However, animals have to accept a considerable amount of defence substances, as their food plants would otherwise be eliminated by pests.

In order to be able to supply densely populated colonies ("metropolises" would be the term for Homo), some animals deliberately grow food. To top it all off, some insect species even opted for monocultures - presumably because these allow higher yields in a small space and in this way feed their colony more easily. A prime example is the so-called mushroom gardens of the leafcutter ants (Attini). These monocultures can reach the volume of the intestinal fluid of large herbivores. In contrast, the ants themselves have lost some of their digestive enzymes because their fungi decompose the hard-to-digest plant material and at the same time provide low-molecular easily absorbable nutrients (DIAMOND, 1998).

7.1 Monocultures

Leafcutter ants cultivate selected mushroom varieties in their burrow, on which they feed themselves and their brood. When a queen-ant flies out to found a new state, she takes some mushroom mycelium with her as seed in a special maw pocket. In each nest there are usually only one or two species (Leucoagaricus, Leucoprinus); however, the ants use many varieties of these. Genetic studies suggest that the ants domesticated and bred several species of fungi separately. In addition, breeding material was apparently frequently exchanged between ant populations (MUELLER et al., 1998).

The right seed alone does not guarantee a successful harvest. Therefore, the ants provide a suitable growing medium, prepare the bed and fertilise it regularly (MUNKACSI et al., 2004). Care measures and plant protection are indispensable. To date, 29 individual work steps have been identified, and a special group of workers is responsible for each of them. As part of the division of labour, the workers develop typical physical characteristics that predestine them for their respective jobs in food production.

Leafcutter ants protect their fungal-gardens from parasites with antibiotics. For this purpose, they harbour Streptomyces, Pseudonocardia and Phialophora in their integuments (LITTLE and CURRIE, 2007). Indeed, older mushroom gardens suffer from the parasitic fungus Escovopsis, which can destroy the entire crop. In laboratory, the antibiotic pesticides of the symbionts suppressed the growth of the parasite. However, they were ineffective against human pathogens, which are normally controlled with antibiotics from streptomyces (CURRIE et al., 1999; WILKINSON, 1999).

Theoretically, the system should soon collapse due to resistance to antibiotics. Nevertheless, this form of monoculture has persisted for millions of years (MUELLER et al., 1998). The ants probably owe this to the evolutionary competition of their symbionts, which leads to ever new active substances. Even more important is the fact that their use - unlike in pig fattening - is neither bound to maximum amounts nor are the active substances used as purified single substances.

In the hands of the farmer antibiotics usually show a double benefit: Firstly, they keep pathogens at bay, and secondly, they promote the growth of livestock. While the use of antibiotic growth promoters has been banned in the EU, the ants unabashedly use the effect of their antibiotics to stimulate fungal growth. With the addition of streptomyces, the cultures produce about ten times the biomass. Whether this immense effect is solely due to the antibiotics, or is also related to the provision of fertilizers such as amino acids, is still unclear (CURRIE et al., 1999). The fact, that leafcutter ants have become the most important herbivores of the tropics in the New World, is due to the fact that they have perfected an agricultural economy that has amazing parallels with human food production (SCHULZ and BRADY, 2008).

The practices of leafcutter ants are by no means unique. Among termites, some species cultivate fungi too. The bark beetle (Xyloterus lineatus) is no different: The female bark beetle drills breeding tunnels into the wood and inoculates them with the spores of the so-called ambrosia fungus with her hairbrushes on her head. Soon the fungus lines the entire duct system and serves as food for beetles and larvae. If other fungi or bacteria begin to grow, the female bark beetle weeds its garden by consuming the weeds. To regulate the moisture in the tunnels, which must not be too low for optimal fungal growth, it also plugs up some sections of the tunnels with bore dust. If the mushroom garden is no longer maintained, because the female beetle dies, it quickly decays and the larvae starve to death (KLAUSNITZER, 2002).

7.2 Livestock farmer

Not only monoculture was invented by nature, long before agricultural science did. Even factory farming isn’t alien to them. Ants, for example, manage large herds of aphids. Some species transport their livestock up to twice a week from one willow to the next. Other ant species have bred Javanese woolly ants (genus Hippeocampus) with modified legs and soles, that are especially suited for clinging to ants. In this way the livestock is depending on their shepherds. In return, the ants protect their livestock from ladybirds, lacewing larvae or parasitic wasps. In doing so the aphids can safely grow into large herds, and the ants keep a close eye on their size. Superfluous animals are killed if necessary (EISNER, 2003).

It may be assumed, that ants not only repel predators such as ladybirds, but also treat numerous pathogens with antibiotics, like leafcutter ants do in their monocultures. However, studies of the therapeutic practices of ants are still lacking. Wood ants (Formica paralugubris) fight bacterial and mycotic infections with selected conifer resins (CHAPUISAT et al., 2007). In return for their protection, care and maintenance, the aphids are "milked" by the ants. When they are touched by the antennae of the ants, they secrete a drop of secretion. Many ant species cover their entire carbohydrate needs with the sugary "aphid milk" or "honeydew" produced by their states (HOELLDOBLER and WILSON, 1994).

The composition of honeydew varies strong from species to species. However, the quantity of honeydew ("milk yield") must also be right (HOFFMANN, 2003). The absolute front-runner and correspondingly popular is the pink tansy aphid (Metopeurum fuscoviride), which releases up to one milligram of honeydew per hour. Ants do not always win the battle for grazing grounds and livestock. So wasps (e.g. Parachartergus richardsi) are keeping treehoppers (Membracidae Sp.), which they have to defend against ants and butterflies (Lycaenidae) (KÖRNER, 1981).

The cornfield ant (Lasius neoniger) even hatches the eggs for the American corn root aphid. The aphid-clutches are maintained in the ants' colonies throughout the winter. As soon as the nymphs have hatched in spring, the ants carry the young aphids to new healthy rootstocks. Other ants build their own stables, or more precisely tree nests, in which they keep their livestock in a very confined space. Some blue butterflies (Polyommatus coridon, Plebeius eumedon) have their larvae raised by ants. In the third larval stage, the caterpillars fall to the ground and are carried to their nest by the relevant ant species, where they are fed. To allow the butterfly larvae to feed undisturbed, the ants build special "earth pavilions" for the blue butterflies under their food plants (HOELLDOBLER and WILSON, 1994). In return, the ants milk the honey glands of the larvae.

Instead of aphids, some ant species have domesticated cicadas, scale insects or butterflies, far larger than their keepers.

8 Hunters and gatherers

Especially under birds, there are talented toolmakers, as they have more need for tools than quadrupedal mammals, due to the fact that their front limbs are transformed into wings: Inca jays, or querrequerre (Cyanocorax yncas) and New Caledonian crows (Corvus moneduloides) poke with trimmed, partly barbed sticks in tree trunks in order to catch maggots (GATOU, 1982; HUNT and GRAT, 2004). Other birds have focused on bait fishing. A green heron (Butorides virescens) (LOVELL, 1958) and a black kite (Milvus migrans) (ROBERTS, 1982) were observed throwing pieces of bread into the water to attract prey. Other species such as e.g. the mangrove heron (Butorides striatus) use anything that might arouse the curiosity of potential prey, such as feathers, fruits or insects (ROBINSON, 1994). Humpback whales (Megaptera novaeangliae), which have a similar handicap as birds with their flippers, catch fish with "virtual" nets. They circle underneath a school of fish and let air bubbles rise all around. A second method is to swim at the surface to create a ring of foam with the fins. Fish enclosed this curtain of bubbles do not dare to escape. This makes them easy prey for the whales (HAIN et al., 1982). The creation of virtual webs is thus just as effective as that of the (real) web of spiders. A brute hunting method utilise polar bears (Ursus maritimus): They throw lumps of ice at seals (BECK, 1980).

Chimpanzees (P. troglodytes) use various tools to catch termites or ants: for example simple flexible sticks, which they sharpen to poke holes in the animals' burrows.  They fray sticks with their teeth so that they look like a brush, in which a great many termites will bite at the same time. (SANZ et al., 2009a und b). They even make wooden spears to impale bushbabies that spend the night in trees. (PRUETZ und BERTOLANI, 2007).

9 Kitchen tricks

In human societies, the harvest or slaughter is followed by processing the products.  What used to be done in the household and later by craftsmen, is now done on an industrial scale. What is not sufficiently digestible by peeling, sifting or de-seeding is still subjected to fermentation and/or heating. Without these techniques, neither most cereals nor the soybean would have become staple foods of mankind. And without them, the earth could not feed the current eight billion people.

Many methods that humans practise to prepare their food, also find their equivalent in the animal kingdom. The shells of eggs, nuts or crabs can be opened with paws, teeth or beaks. sea otters (Enhydra lutris) crack open snails (abalones or abalones) by first taking a stone from the seabed with their free paw. At the water's surface, they turn onto their backs, place the shellfish on their bellies and crack it open. Mongooses (Herpestes edwardsii), who catched a (non-poisonous) millipede, throw the armoured animal, which has been rolled up into a ball, violently against stones or trees until it bursts (EISNER, 2003). Birds drop snails, shells or nuts from great heights (BECKER, 1993). Many bird species, such as chicken birds (Galliformes), harbour stones (gastroliths) in their gizzards as a mechanical digestive aid.

A bottlenose dolphin (Tursiops aduncus) was observed repeatedly biting at cuttlefish (Sepia apama) and holding it in flowing water until the ink has been washed out. Then he dragged the prey along the bottom until the calcareous pulp could be detached. Only then the prey was eaten. The preparation improves the nutritional value considerably: the melanin pigments of the ink impair digestion, and the backplate is difficult to digest (FINN et al., 2009).

Even some butterflies can’t do without preparing meals, for example if they cannot consume and digest pollen. The members of the genus Heliconius have found a way to absorb the amino acids contained in the hard pollen grains. They break up the ingested nectar and mix it with the pollen grains. They stir this mixture with their mouthparts for hours until the pollen's own enzymes release proteins and amino acids. Now the butterflies suck up the protein rich nectar solution (O'BRIEN et al., 2003; GILBERT, 1972).
Parrots in the Brazilian rainforest detoxify their food by regularly nibbling clay from certain cliffs, which binds alkaloids from the food. In doing so, they use the same clay as human societies do. In this way the antinutrient substances are excreted, unchanged, together with the kaolin. Geophagy is widespread; in the Amazon region alone, this behaviour is known from monkeys, tapirs, peccaries, deer as well as various chicken birds from the Cracidae family. In Central Africa, forest elephants, lowland gorillas and mountain gorillas eat regularly clay (MAHANET and KRISHNAMANI, 2003).

Detoxification through fermentation is also practiced in the animal kingdom. The great grey shrike (Lanius excubitor) impales extremely poisonous grasshoppers on thorns or barbed wire. There, the prey matures for two days until the poison has decomposed. During this process, the grasshopper changes colour. The shrike only eats after the colour has been changed - and then only the non-toxic parts, he spurns the rest (YOSEF and WHITMAN, 1992).

Another curious, but not so rare behaviour is the washing of food. Marabous (Leptoptilos crumeniferus), for example, washes dung beetles, that they had fished out of elephant dung before eating them (Wickler and SEIBT, 1978). Crows (genus Corvus) dropping whelks from great height, sometimes dipped the shattered shells into puddles to remove splinters (Zach, 1978) Other animals seem to be less concerned about cleaning than about moistening dry food. A crane (Quiscalus lugubris) dipped dry bread before feeding it to its offspring (MORAND-FERRON et al., 2004).

Of course, the Japanese red-faced macaques (Macaca fuscata) are not to be missed: for the first time in 1953, a macaque-girl was observed washing sweet potatoes, which had been laid out in the sand by researchers as an attractant, before eating them. This was quickly imitated by her playmates. Today, washing food is standard practice in this ape society. However, the animals are not only concerned about cleaning. When they were offered already washed sweet potatoes, they still went to the beach with them - apparently they liked salted sweet potatoes better (KAWAI, 1965). In a zoo in Madrid, chimpanzees beat the fruit against an edgy wall spot until a juicy pulp was produced, which is licked off the wall (FERNANDEZ-CARRIBA and LOECHES, 2001): Originally, a toothless monkey lady had developed the technique there. Juice extraction is also known from capuchin monkeys (HEINEMANN, 2000) and probably serves to reduce the fibre content, as the remains of the fruit are spurned.

Wood forms tannins, which negatively influence the nutritional value by its reaction with protein. For detoxification, beavers (Castor canadensis) soak branches in water. They choose woods according to their content of repellents: Low-tannin species are eaten directly on land, whereas high-tannin species are eaten only after they have been in water for several weeks. In vitro, soaking reduced the tannins by up to 60 percent (MÜLLER-SCHWARZE et al., 2001). Voles (Microtus pennsylvanicus) gnaw off branches of young coniferous trees in winter and leave them on the snow for two days. This reduces the polyphenol content to a level equivalent to that of the animals' summer diet (ROY and BERGERON, 1990). The North American whistling hare (Ochotonia princeps) collects branches of Alpine avens for its winter supply, which he spurns in summer. At the end of winter, the content of secondary plant compounds in the branches is half as low, so that he can eat them (DEARING, 1997).

In temperate latitudes with winters, stockpiling is required so that the result of the collecting passion does not rot. This is not only true for squirrels or hamsters. Some animals preserve their perishable prey before storing it. Hornets coat killed bees with a secretion to increase their shelf life (HERZNER et al., 2007). In their turn honey bees, coat their hive with a thin layer of propolis to protect against infections. Honey itself also contains antibiotic substances that preserve it - in addition to its low water and high sugar content.

10 Fire at will!

The most important achievement of humans is the use of fire for cooking. According to WRANGHAM and CONKLIN-BRITAIN (2003), the first cooking fires may have burned as early as 1.9 million years ago, at a time when the modern human body was beginning to evolve. Homo erectus was 60% larger than its ancestors and brought with it the largest increase in brain mass ever observed. This may be seen as an indication of the successful use of fire.

According to WRANGHAM and CONKLIN-BRITAIN (2003), a vegetarian raw-foodist, with a daily calorie requirement of only 2000 kcal per day, would have to eat five kilograms of fruit and vegetables to meet this requirement - albeit from today's cultivated forms. If we take wild forms of vegetables as a basis, the nutritional requirement is significantly higher. Whether our reduced digestive system will be able to cope with this in the long term is twofold. If the diet is supplemented with raw meat, almost 3 kg of food are still needed. In comparison, cooked food requires less than 2 kg of food per day: this relieves the digestive system.

Cooking means a high energy gain: on one hand, due to the easier digestibility of starch and proteins, on the other hand, the effort for detoxification of many heat-labile antinutrients in plants is omitted. In addition, numerous pathogens, whether microbes or parasites, which could enter the body through food, are killed (CARMODT and WRANGHAM, 2009): This increases life expectancy. Last but not least, heated food also contributes energy in the form of heat. Fire also enabled the use of inedible plants, which expanded the human menu and made it possible to colonise virtually the entire globe (WRANGHAM and CONKLIN-BRITAIN, 2003).

Animals also appreciate cooked food. WOBBER et al. (2008) offered raw and cooked food (carrots, potatoes, meat, apples) to chimpanzees, bonobos, gorillas and orangutans in food choice experiments. Beforehand, the animals could try cooked food to avoid neophobia. All of them preferred the more easily digestible cooked food. But even chimpanzees that had never been given cooked meat immediately went for the cooked version. The authors concluded from this - as well as from experiments with ground or mashed food - that the softer texture was responsible for this. The results support the hypothesis that the use of fire for food preparation may have manifested itself very quickly as soon as the first hominids came into contact with it - for example through bush fires.

Usually, bushfire means danger for animals. But some seem to derive culinary benefit from it: Falcons hunt the fleeing animals (NIMUENDAJU, 1946), woolly-necked storks and king vultures gather grilled insects or reptiles when the fire has moved on (KASOMA and POMEROT, 1987; HARPER, 1936). In Australia, numerous species of animals, such as reptiles, birds and rats, have been observed specifically searching for food in areas where bushfires took place (BRIGHT, 1994). Some birds patrol along fire lines in search of scorched insects (JONES, 2002). It is doubtful whether birds - as eyewitnesses claim to have observed - transport smouldering branches to dry spots to start new fires (GOUDSBLOM, 1986). [Added in 2023: The Australian firehawks, black kite (Milvus migrans), whistling kite (Haliastur sphenurus), and brown falcon (Falco berigora) spread bushfires by transporting burning sticks in talons or beaks to smoke out and roast their food. (BONTA, 2017)] It is a fact that wild chimpanzees search for charred food after bushfires and that they - as well as orangutans - tried to imitate the lighting of a campfire in the wild (MCGREW, 1992).

The consequences of an unprocessed, say natural diet, are evident in the great apes. They spend a large part of their time eating and digesting. Chewing alone requires about five hours a day (GIBBONS, 2007). Meanwhile the human digestive tract is so adapted to prepared food that there rise problems with raw food. In addition to digestive problems, pure raw food diets usually cause calorie deficiencies. In women, the menstrual cycle stops, because the body has too few reserves for pregnancy (KOEBNICK et al, 1999). H. sapiens sapiens owes the evolution of its brain to cuisine. Due to breeding and modern agriculture he won his freedom, and, not charged by the difficult obtaining of food, he could devote himself to cultural work. This created the base for the cultural achievements of the coctivors.

Acknowledgement

We would like to thank Dipl.-Biol. Andrea Fock for her highly appreciated professional support, Mr. Karl-Ludwig Leiter for preparing the graphics and Mr. Piet van Veghel for the translation.

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English Editor: Josef Hueber