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The Origins of Agriculture: Prologue

CHARLES A. REED

The process of living involves the directed control of the acquisition and use of energy. In the long history of the cosmos, energy flows from centers of concentration to regions of diffusion, but in the process, as Homer Smith (1932) so succinctly said, life is a temporary eddy in the second law of thermodynamics, a temporary — but only a temporary — reversal of entropy.

Each protoplasmic entity must find its own energy or, as with a green plant, be placed in such a position that energy comes to it. Animals find energy by finding food; they eat (sensu lato). An amoeba surrounding and ingesting another protozoan, an octopus catching a crab, a cow grazing in a pasture, a fox eating mice, and a man picking and eating wild berries are all akin; they are using their individual protoplasm, their own private protoplasmic system, to provide themselves with the energy necessary for their life processes. Each is a "primary energy trap," not in any sense in relation to its position on the food web — that concept is not involved — but simply because it acquires energy via food by no other means than its own protoplasm. Also, to the degree that it maintains its own con- tinuing individuality (escapes enemies, conserves energy) by using only its own protoplasm and its own cellular system, it functions as a primary energy trap.

Most organisms, whether prokaryote or eukaryote, plant or animal, unicellular or multicellular, are simply primary energy traps; the function without accessory nonprotoplasmic devices. Evolution is adaptive, obvi- ously, and a considerable variety of complex structures has evolved which, while not strictly living, are still an integral part of the proto- plasmic system. Bone, for instance, is internal, replaceable, repairable,

Origins of Agriculture, edited by Charles A. Reed, De Gruyter, Inc., 1978. ProQuest Ebook Central, http://ebookcentral.proquest.com/lib/sjsu/detail.action?docID=3044546. Created from sjsu on 2021-01-16 19:43:11.

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1 0 CHARLES A. REED

porous, filled with tissue fluid and permeated by cells, and at the molec- ular level is a dynamic part of the biochemical system, even though the actual crystals and spicules of bone are extracellular. Bone — even the bone of an armadillo's "shell" — is a functioning part of the inner animal, and is thus part of the primary energy trap.

By contrast, a variety of noncellular structures or merely things, pro- duced by the organisms or existing naturally in the environment, is utilized by animals for the acquiring or conserving of energy, and these can be called "secondary energy traps." (Tools, to be discussed later, are a special kind of secondary energy trap.)

A total catalog and discussion of secondary energy traps would fill a volume larger than this book, but some examples are: secreted, non- cellular and nonliving external tests or shells, such as those of Foramini- fera and Mollusca; natural cover, holes, crevices, etc., sought and utilized by animals for protection or by a predator for concealment, or similar structures (burrows) constructed by an animal for the same purposes; external secretions (mucus, silk, perspiration, body oils, a variety of tox- ins); tools, either objects naturally occurring in the environment and used without modification or those shaped and thus manufactured; social behavior, whereby the energy expended by the individuals of a group is pooled between them and benefits can accrue thereby which would be impossible for the lone operator (group hunting, food sharing, systems of communication, aid from kinfolk, economic networks, etc.).

Different animals accomplish the same ends differently, some with primary, some with secondary energy traps. A few such contrasts, as examples, are outlined in Table 1.

As typical of evolutionary sequences, a structure evolved in correlation with one function may be modified by secondary or tertiary adaptations as the result of subsequent natural selection. Thus, the silk produced by spiders, ancestrally used as guidelines and to line burrows, in most groups also became a food-catching device, and in some the web then also serves as a channel of communication by which a male may approach a female without being attacked; he must activate the web in a way that a strug- gling insect would not. Another species of animal, only distantly related, may use some part of the web as a secondary energy trap of its own, to become cross hairs in a transit; this same species takes the stuff of which cocoons are made, a secondary energy trap produced by an insect larva, and modifies that silk into its own secondary energy traps, to win a mate or buy an emperor's favor.

Modifications of behavior, as with the actions of the male spider men- tioned above, are often part of such continuing evolution of secondary

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The Origins of Agriculture: Prologue 11

energy traps; they serve to continue the animal's energy system, which otherwise might be abruptly terminated. Thus, many animals secrete noxious substances to protect themselves from predators. Such poisons are obviously secondary energy traps, protecting the animal's own energy system from oblivion. Some animals, however, improve their efficiency by modifying both behavior and morphology; thus, the poison may be sprayed over an attacker (the bombardier beetles), or an appendage is used to wipe the poison on aggressors (one species of harvestman, or daddy longlegs; Eisner, et al. 1971). Many types of behavior, that of both solitary and social animals, are further examples of the principle that secondary energy traps are subject to natural selection; they have evolved and continue to do so.

From the viewpoint of reproduction, parents (and often other adults) are secondary energy traps, providing at the minimum some food in an egg, and often additional food and many services (protection, teaching) to the young. A nursing mother, to a baby, is a secondary energy trap. Many and complex are the secondary energy traps by which genetic (and in some cases cultural) endowments are passed from one generation to another.

These examples undoubtedly can be found in all phyla of animals — I can think of one such in the Protozoa, for instance — but mention of a few cases among the vertebrates will illustrate the principle. Among the primitive jawless fish, male lampreys prepare a depression ("nest") on the stream bottom in which the female spawns (Brigham 1973); salmon and many other bony fish do the same. This minor depression is some pro- tection to the eggs and thus, to the hatching young, is a secondary energy trap. The eggs of many frogs are laid in a mass of noncellular jelly — a secretion of the female's reproductive system — which inhibits predation. The young of reptiles and birds are protected by an enveloping shell, and usually are deposited in nests, some extremely elaborate. Uni- versally among mammals and almost universally among birds, the young are furnished food, and in many such animals are additionally given the time and effort of teaching. Among a few animals, humans for instance, the expenditure of energy by parents on the young continues long after the latter have reached reproductive age. Sometimes, one thinks, parents are little more than secondary energy traps for their offspring.

Tools, however defined, are all secondary energy traps. In dictionaries and in the numerous articles on tool using among animals, one finds lack of agreement on the precise meaning of the word "tool" (Alcock 1972). I do not intend here to pursue this semantic topic; van Lawick-Goodall (1970) has discussed the problem to some degree in her excellent summary

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12 CHARLES A. REED

Table 1. Some comparisons between primary energy traps and secondary energy traps

Animal Action or function Primary energy trap Secondary energy trap

Most predators of Breaking of egg Use of body parts ostrich eggs of ostrich

Man and Egyptian Breaking of egg A rock, thrown at vulture® of ostrich the egg

Whalebone whales Filtering krill Use of whalebone6 and tongue

Most filter Filtering plankton Use of part of body feeders0 as filter

Some filter Filtering plankton Mucous traps as feeders filters'1

Robber fly Catching insects The robber fly is a direct predator

Orb-weaving Catching insects Use of spider web spider as a trap

Trap-door spider Catching insects Prepared, silk-lined burrow with hinged door®

Polar bear Protection against Fur', fat, warm Seeks or prepares cold blood shelter, particular-

ly for sleeping Man Protection against Fat, warm blood Clothing, dwelling,

cold fire«

Some insects Protection Pupa case11 between stages

Some insects Protection Cocoonh between stages

Most crabs Protection against Use of claws; Threat, a direct aggressors escape communication

Hermit crab Protection against Sea anemone Dardanus octopus Adamsia, placed

on adopted shell1

Hermit crab Protection against Tolerance of com- Pagurus larger hermit mensal hydroids

crabs which live on some abandoned snail shells'

Eolidoid Protection against Discharge of sting- nudibranchs aggressors ing cells

(nematocysts) derived from consumed coelenteratesk

tt J. van Lawick-Goodall and H. van La wick (1966); see also Chisholm (1954) for reference to a similar practice of Australian buzzards in breaking emus' eggs.

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The Origins of Agriculture: Prologue 13

of tool using among vertebrates. She regarded a tool as an object neces- sarily manipulated; thus, a rock thrown at or dropped on an egg is (in her opinion) a tool, whereas a rock against which an egg is thrown or upon which it is hammered is not a tool; knitting needles are tools, whereas yarn or the sweater produced by the knitting are not tools; a twig used by a chimpanzee to pull termites from a termite mound is a tool, but the nests the chimpanzees make — or that birds or other mam- mals make — are not tools.

Considering the problem from the viewpoint of secondary energy traps, the differences between these categories of tools and nontools (as used by

b In the mysticete whales, the filter (the so-called "whalebone") is an epidermal structure, and, thus, cellular and originally living tissue. c The filter, whether antennae or mouthparts or other, is a part of the cellular structure of the animal's body. d Mucus is a secreted, noncellular, nonliving substance. Even the mucus of pharyngeal filter feeders such as tunicates and Branchiostoma {— Amphioxus) amongst chordates is a secondary energy trap, since the whole of the digestive cavity of any metazoan is not INSIDE the animal but is merely a part of the external universe that is surrounded by the animal. The fanciest filter feeder that comes to mind is that of a marine pteropod (a particular kind of free-swimming, shell-less snail) which spreads a filmy net of mucus in seawater and then consumes it along with the trapped plankton (Gilmer 1972). e The "home" of the trap-door spider is of course a secondary energy trap in that it hides and protects the spider, thus conserving its energy and continuing its being, but the "home" is more; as a camouflaged lair from which the spider can spring upon its prey, the "home" is a basic part of the feeding pattern, thus having a double function as a second energy trap. ' Hair, like whalebone, is composed of cells; these, once alive, are a part of the body, not a noncellular secretion from it. β Fire was the first chemical reaction (oxidation) used as a secondary energy trap by man. Although man was the first to use fire, the slower oxidation of rotting vegetation has been used for millions of years by various other animals to control temperatures of domiciles (as with some ants) or nests of eggs. See Clark (1964) for a most interesting case among birds. h A pupa case is a part of the animal's body, but a cocoon, like a spider's web, consists of a nonliving, noncellular secretion. 1 Reilly and Stone (1971). The abandoned snail's shell which the hermit crab adopts is also, of course, a secondary energy trap for the crab using it, as it previously was for the snail. 1 Pagurus, where in competition with populations of larger hermit crabs, may have his adopted snail shell taken from him by one of the larger hermits. If, however, an individual of Pagurus can find an empty snail's shell with hydroids growing on it, he can probably occupy it safely, as the populations belonging to Pagurus have evolved a natural immunity to the poison of the hydroids, an immunity lacking in the species of larger hermit crabs, which sometimes attempt to occupy such a shell with hydroids but are soon forced to leave (Wright 1973). k The nudibranchs (shell-less, noncoiled, surface-creeping marine snails) feed on hydroids, jellyfishes, sea anemones, and corals; the delicately triggered nematocysts of these coelenterates are passed intact through the wall of the digestive tract and then through the tissues of the nudibranch, to be stored in special sacs in spurs on the back, discharging finally against aggressors attacking the nudibranch (Zeiller 1971).

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14 CHARLES A. REED

van Lawick-Goodall and by Alcock) are not so important. All of the examples listed above are secondary energy traps in that the various objects provide means for utilization or conservation of energy which would not be available to a particular animal were it limited to the use of its own body without the additional help of the external object.

Unless one wishes the meaning of the word "tool" to include all second- ary energy traps, a definition of the subcategory intended is obviously necessary, and probably the concept agreed upon by van Lawick-Goodall and Alcock is the easiest, even if to my own mind unduly restrictive. I myself have always automatically thought, in agreement with Lancaster (1968), that nests of birds in particular, but also those of such mammals as build nests (chimpanzees, for instance) are tools; they are built by the animal of objects manipulated to form a structure, and are used for a definite purpose. However, once one has crossed the line of the definition established so succinctly by Alcock — "Tool-using involves the manipu- lation of an inanimate object, not internally manufactured, with the effect of improving the animal's efficiency in altering the position or form of some separate object" — one would find difficulty, I can see, in locating another definitional boundary.

This digression into the use of the word "tool" is necessary in this introductory chapter because cultivated plants and domestic animals have sometimes been regarded as living tools of humans. By the above defini- tion they would generally be excluded. A harness is a tool if used to pull a wagon which moves an object in a way that increases human efficiency; in this operation the wagon is also a tool, but the horse that wears the harness and pulls the wagon is not a tool. However, for the man involved, all three — horse, harness, and wagon — are secondary energy traps. Glue in a pot is not a tool (although presumably the pot is), but the same glue actually used in the process of manufacturing becomes a tool — or does it? Alcock stated that a tool must be an object, and perhaps glue is only a substance. A domestic animal would become a tool if one used a dead chicken to beat another chicken to death and then ate the second chicken. Such gentle chiding aside, the concept of tool use probably does have value in that manipulation of objects (and/or substances) producing changes which increase the user's efficiency would have selective value and thus may well be evolutionarily important. For the purposes of the discussion being presented here by me, the concept of secondary energy traps seems more fundamental.

With regard to feeding and food getting, an efficient technique for making energy available would be for the feeder to have control over the supply of food, whether that control be called husbandry, gardening,

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The Origins of Agriculture: Prologue 15

horticulture, herding, food production, or agriculture in general. Any action by the feeder which increases the yield of a food in a given area over the natural yield turns the particular plant or animal being fostered into a secondary energy trap for the feeder — the one who then utilizes the additional energy produced. The dominant population has, thus, evolved a mechanism for utilization by itself of a greater part of the energy available in a given environment than was available to its ances- tors ; the general trend that results is that the population increases over that of the ancestors.

Symbiosis and other kinds of mutualism are not rare in the living world; even such closely related intermutual benefits as the combination of an alga and a fungus to produce a lichen, or the combination of termite and intestinal flagellates to produce a wood-utilizing animal are not so rare. However, the propagation and protection of one species by another, to the benefit of both, ARE relatively rare in the biological world.

The leaf-cutting ants (genera Acromyrmex and Atta, of the tribe Attini) (Weber 1972) are the most specialized and the most successful of the "gardening" or agricultural ants. The ants cut leaves, blades of grass, or flowers, carry them to underground nests, clean them and chop them, force the pieces into prepared ground, and then transplant mycelia of a particular fungus onto the pieces so implanted. (In competition with human farmers, the ants are sometimes more successful, stripping fruit trees of their leaves.) The fungus grows luxuriantly on the rotting pieces of vegetation, and the ants thrive by eating the fungus. In parts of South America these ants plus the termites comprise the greater part of the animal biomass.

Other kinds of attine ants behave similarly, but use insect droppings or pieces of already-decayed vegetation upon which to grow their fungi. As termites are to flagellates, so are the attine ants to their fungi; neither insect can survive without its symbiotic organism. Each insect has its neural system programmed to maintain the symbiont; the termite, stripped of its necessary fauna by a molt, will beg and receive from a co- worker an anal drop teeming with the necessary protozoans, and the ants instinctively accomplish all of the necessary complex activities to maintain their gardens. The difference, and the reason we call the ants agricultural, is that they prepare the soil, maintain proper temperature and humidity, and plant their fungus. In neither instance can one of the partners survive without the other, but the ants — instinct bound as they seem to be — are not without some modicum of versatility; a population of ants in the laboratory, denied vegetation but furnished with nutrient agar, utilized the unaccustomed substance, planted their mycelia, and

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successfully reared both fungus and a new generation of ants. Another group, denied their own species of fungus, adopted another species which before had been grown only by another kind of ant.

Numerous other kinds of ants have domestic animals; none of these ants are also horticulturalists, nor do any of the fungus-growing attines keep livestock. Thus, no ant is a complete agriculturalist; only man has achieved that unique capability. All of the ants' livestock (aphids, leaf- hoppers, and scale insects, mealybugs and other coccids) belongs to suck- ing insects of the order Homoptera. Each homopteran inserts a hypo- dermic-like proboscis into the phloem sap of a plant, and sucks much more fluid than it can use. The excess, sweet and nutritious because of contained sugars, fats, and proteins, is normally ejected in jets or droplets from the hindgut. (Dried, this plant sap becomes the "manna" of Exodus, and is supposedly still gathered and eaten by the Bedouins of Sinai.) In both liquid and dried form this "honey-dew" is utilized by many kinds of insects, but certain ants have entered into productive symbiosis with certain homopterans. Most such ants are restricted to one species or a few related species of such sucking insects, but many and strange are the intermutual adaptations (Michener 1951; Sudd 1967; Wilson 1971).

In general, the ants tend, guard, defend, and sometimes transplant their livestock. In return, the aphids particularly, but some of the other homopterans as well, learn not to eject their liquid or kick it away with their hind feet (their typical solution of an obvious problem of sanita- tion), but instead to wait for a herder, and, being stroked by the ant's antennae, let a drop ooze out gradually, to be sucked up by the ant. Indeed, if the ant is disturbed at the feast, an aphid will pull the drop back in. (Cows, which function on a different principle, cannot do this.)

The ants drive off predators, and sometimes, from earth and plant debris, build protective sheds or tunnels for their charges. Greater care is given by ants which nest underground to aphids which feed on rootlets; here the ants care for the eggs of the livestock, as they would for their own, maintain optimal temperature and humidity, and when the aphids hatch, a cleared area is prepared around a rootlet and the aphid is carried to the spot. Indeed, these underground ants are reported sometimes to clip the wings of the sexual, migratory generation of aphids, thus keeping the eggs in the nest.

Certain ants keep scale insects instead of aphids; of these, those in Java move their livestock as desired on their own backs; at a given tactile signal the tiny coccids climb nimbly aboard. A new queen, leaving the nest to start a new colony, will be carrying one or more of the scale insects from the parent colony.

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The Origins of Agriculture: Prologue 17

While several examples are known of Homoptera which have not been found except in ants' nests, only one case seemingly is known where both the ant and its domesticate are completely dependent upon each other (Flanders 1957). This population of ant, which lives in Colombia, keeps a particular scale insect; neither ant nor coccid is ever found separately. The nests, which are underground, are always small, and both sanitation and increases of population present potential problems; the ants have solved these problems by rotating the scale insects at the feeding stations (rootlets); typically only 30 percent of the livestock is allowed to feed at one time. When a new queen leaves, she carries a scale insect gently in her jaws as she flies; without the proper "cow" the new colony would be a failure.

Thus, we see that while some ants are agriculturalists, profound differ- ences exist between such ants and men: the ants, although capable of some learning by experience (as tested in the laboratory, Sudd 1967), generally function at an instinctive level; only a few kinds of ants, of one tribe, are gardeners, but many kinds of several subfamilies keep livestock. By contrast, all men belong to but one species, and many if not most human farmers keep one or more kinds of domestic animals while at the same time cultivating plants. In that practice of mixed farming, man is unique in the animal kingdom. Ants are generally limited to the agri- cultural practices of their nearer ancestors, and must depend upon the slow mechanisms of evolution for any change, while man is culturally adaptable.

Aside from man and the relatively few kinds of attine ants, horticulture is unknown among animals (insofar as I am aware), with the possible exception of the curious case of a marine amphipod (Crustacea), Dulicha rhabdoplastis. This tiny animal, a small relative of the better known beach-hopper or sand flea, builds its own elongate, cylindrical, dimin- utive "farm" on the tip of a spine of the giant red sea urchin Strongylo- centrotus franciscanus, living on the bottom of Puget Sound, Washington, United States (McCloskey 1971). The farm consists of the tiny amphipod's own feces, carefully placed and glued into position to make an elongate rod, from 2.5 centimeters to almost 4.0 centimeters long. In the summer this rod supports a luxuriant growth of diatoms, a form of unicellular plant, upon which the amphipod feeds, keeping the population spaced by the eating of the larger individuals. Other organisms, which could foul the surface, are carefully removed. The amphipod is not an obligate farmer, for during the winter and in part during the summer it is a filter feeder, ascending to the tip of its rod and spreading its two elongate, multisetaed antennae at right angles to the bottom current. Bits of plank-

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ton caught in the intermeshing setae are scraped off as each antenna is drawn through the mouth.

We do not know that Dulicha rhabdoplastis is a true horticulturalist, for the incomplete studies to date have not produced evidence that the amphipod plants the diatoms; instead the situation seems to be more similar to several examples known from ethnographic studies, where man weeded and might otherwise protect a patch of esteemed natural vegeta- tion. The amphipod, however, has gone a step beyond this simple pre- agricultural situation, for he carefully prepares an environment which is not only his own home but is an optimum place for the growth of one of his favored foods.

Although man has used individuals of his own species as slaves, in agricultural work and otherwise, thus converting them to secondary energy traps on an economic and social level with domestic animals, slavery is not necessarily correlated with agriculture, either among humans or other animals. Some ants are slaveholders; they raid the nest of certain other species of ants, capture the inert pupae, and bring these back to their own nests. The ants that emerge from the captured pupae then become slaves, procuring food for their masters and feeding and otherwise caring for their larvae. The slaves are not themselves used for food, nor are they bred in captivity. The populations from which the slaves are captured are not dependent upon the slaveholders, but the slaveholders cannot survive without slaves. In this case, the slaves are obviously involuntary secondary energy traps for their masters, but the situation does not involve agriculture; instead it is more akin to the case of men in parts of southeastern Asia who train macaques to climb coconut trees and loosen and drop the nuts for the men to collect (Bertrand 1967). The master gets the coconuts, while the slave, belonging to another spe- cies, escapes punishment and is fed as the reward for his success. Agri- culture may be but is not necessarily involved, nor are the macaques domestic. They are wild animals that are tamed and trained, as also are elephants who are caught and trained to work.

Agriculture, which includes in the broadest sense the domestication of either plants or animals (or both), is not a common phenomenon. Horti- culture amongst the ants was probably innovative in the population ancestral to the tribe Attini, and the practice there has had its own adaptive radiation, coincident with that of the several genera and species of that tribe. The case of the diatom-feeding amphipod, Dulicha rhabdo- plastis, shows a possible avenue toward true horticulture among non- human animals, particularly arthropods.

With men as with ants, a plant or animal which is protected, reared,

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The Origins of Agriculture: Prologue 19

and maintained (whether truly captive or not) is a secondary energy trap if it yields a return in energy. Insofar as men or ants furnish labor or protection or food or fertilizer for their charges, the dominant species serves in turn as a secondary energy trap for the domesticate! Man, how- ever, is a canny beast; he will not long serve as a secondary energy trap for a domesticate if the return be less than the investment. Ants, of course, will not do so either, but the pattern is different; man would shift his ground, growing a different crop or quitting the soil for city life, but the ants (if obligate agriculturalists) simply starve to death, as do men some- times in similar circumstances.

Domesticates which are totally dependent upon ants for survival undoubtedly have been changed genetically by the selective pressures of life under the restrictive conditions of the care by the ants. For similar reasons, plants and animals which have been domesticated by man have almost always been changed genetically — sometimes purposely, but often not; some (hexaploid wheats, maize, bulldogs) have undergone more change, and others (two-rowed barley and cats) less.

Domestication is not a clean-cut concept, and the word is difficult to define. I have become lost in this semantic bog before, and so avoid the morass now. The truth is that all situations are known to occur, from the free-living "wild" animals and plants, through such cases as animals of zoos and circuses (animals which often breed in captivity under condi- tions of controlled mating), to semidomestic or recently domestic species (white rats, "domestic" cats), to the typical domestic plants and animals (barleys, wheats, oats, rye, millets, etc.; sheep, goats, cattle (sensu lato), pigs, horses, guinea pigs, camels, llamas, etc.), to those forms which cannot survive without the assistance of man (maize, Ancon sheep, numerous toy dogs). These and any other categories, however, always have multiple exceptions. And additionally, one is always faced, at the one extreme, with the relative ease of taming some "wild" animals (Amer- ican bighorn sheep, wolves, pigs), and at the other, with the ease with which many, but not all, of our well-established "domestic" animals (pigs, dogs, horses, water buffaloes) become successfully and even fiercely feral.

Each population of plant and animal that we call domestic — each of the many kinds involved in the topic agriculture — is a subject of its own. Yet agriculture is certainly a unit — the totality of the human practices involving those living secondary energy traps which man plants, breeds, nurtures, grows, guards, preserves, harvests, and prepares for his own use.

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