From the "viewpoint" of living organisms at the level of the species, biological evolution must be regarded as a predominantly divergent process. The injection of a few members of a given type of lifeforms into a virgin environment normally results in an explosive "adaptive radiation." Species rapidly multiply to fill all possible available niches.

From the "viewpoint" of the whole environment, however, evolution is primarily convergent. Though there are many exceptions, the general rule is that species evolving in roughly similar environments tend to find similar solutions to similar problems of survival.

For instance, the deep-sea niche (where high speed may be required to feed on fast-swimming prey) has given rise to a striking example of parallel evolution. The large, streamlined "fishy" shape has evolved independently at least four times on Earth: The mosasaur (an extinct Cretaceous marine lizard), the ichthyosaur (an extinct Jurassic sharklike reptile), the tuna (and other modern fishes, including sharks), and the cetaceans (modern mammals, including dolphins).

Examples abound. Ants and termites belong to different insect orders, yet they have evolved similar societal and architectural forms. Marsupial "psuedomamnals" evolved independently in Australia and South America, filling niches identical to those occupied elsewhere by their physiological cousins the mammals. In earlier chapters we discussed the convergent evolution of legs, wings, eyes and other bodily organs. It is probably safe to conclude that "anytime you get extensive convergence of evolution along different lines you must be dealing with an almost certain process."²²

Based on their observations of convergent evolution in similar environments, human zoologists and paleontologists have proposed a number of evolutionary "laws". These "laws" appear generally true on Earth, and may be expected to have some measure of applicability to extraterrestrial lifeforms as well. Here are a few of the author’s favorites:

1. The total biomass of the entire system tends to increase and become maximized over time. (Lotka’s Rule)
2. The general process of evolution involves the development of new organ systems, increasing complexity, and greater efficiency.
3. Progressively more modern forms tend to have fewer, more specialized segments and appendages. (Williston’s Law)
4. Species tend to evolve to larger sizes. (Cope’s Law)
5. Major evolutionary steps, once taken, are never reversed. (Dollo’s Law)
6. Allied races of warm-blooded animals tend to be larger in colder climatic regions. (Bergmann’s Rule)
7. Mammals inhabiting tropical regions tend to have shorter and less woolly coats than related lifeforms in colder climatic regions.
8. Herbivores have hooves; carnivores have claws. (Cuvier’s Law)
9. Limbs and tails of related species are shorter in colder climatic regions. (Allen’s Rule)
10. Organisms living in warm, humid areas tend to be more heavily pigmented than related species living in cool, dry regions. (Gloger’s Rule)

Examples of this sort can be multiplied indefinitely. Dr. Bernhard Rensch lists more than 100 such "laws" of evolution, to illustrate his thesis that "evolution is largely a lawful process, and with regard to the effect of continuous mutation and natural selection it is also a determinate process."²⁸⁹⁷

There is one other general rule of evolution, often ignored but of major significance nevertheless: Species tend to become extinct. This simple truth is rarely appreciated fully. It is a fact that more than 99% of all species that have ever trod the Earth are now extinct. While more than 3,000,000 species are alive today, more than a billion animal and plant species have arisen at one time or another in Earth’s past.^{624, 2440} Most evolutionary experiments prove to be dead ends or are insufficiently adaptive to changing conditions. Extinction, not survival, is the general rule.¹⁶⁶⁸

Table 20.1 Average Taxonomic Evolution Rate, in Millions of Years per Unit of Taxonomic Classification(after Rensch449)

How fast does evolution occur on other worlds? At least three different "rates of evolution" have been studied by Earthly zoologists.

• First there is the "morphological rate" — the speed at which the size and shape of organisms belonging to a given species evolves over time. For instance, it has been shown that the average dimensions of horses’ teeth have increased at a rate of about 0.1% per 1000 years.⁴⁴⁰
• Another measure of the velocity of evolution is the "taxonomic rate." As shown in Table 20.1, the taxonomic evolution rate measures how fast new subspecies, species, genera, and so forth arise naturally.
• Finally, the "genetic rate" of evolution specifies the speed at which alterations in genes are occurring in the subject population. Measured genetic rates generally confirm the values given in Table 20.1.*

A wide variety of different factors operate collectively to increase or decrease the rate of evolution of species on any given planet. It is true that modern geneticists recognize evolution is primarily a function of genetic variation stored in the species’ general gene pool. Evolution advances by reshuffling previously accumulated gene types by a process known as "recombination." (See the discussion of the benefits of sexual reproduction in (Chapter 12). Nevertheless, the primary and ultimate source of all genetic variation is mutation.³²⁰⁸

• If the mutation rate is too low little variability is retained, leaving a smaller inventory of possible adaptations for natural selection to act upon in response to environmental changes.
• If the mutation rate is too high, desirable characteristics are mutated away or are selected out before they have a chance to be assimilated into the gene pool.
• Thus there exists an optimum range of mutation rates for any class of organisms.³⁰⁵

The average background level of radiation at the Earth’s surface is about 0.12 roentgens/year. About one-third of this is cosmic rays from space. The other two-thirds comes from terrestrial sources such as natural crustal radioactivity and deposits of potassium-40 in our bodies.³⁹⁰ What effect on the mutation rate — and on evolution — does this background radiation have?

• Among smaller organisms, often as much as 100-1000 times the background is required just to double the natural mutation rate.
• Among larger organisms, as little as 3-10 times above background may produce a similar effect over the whole body.
• It would appear that on Earth today natural radiation accounts for only a small fraction of all spontaneous mutations.

The situation may have been much different in the past. I.S. Shklovskii and V.I. Krassovskii, two distinguished Russian astrophysicists, have calculated that Earth may have passed within 10 parsecs of a supernova event perhaps a dozen times since its formation 4.6 eons ago. In each case, the scientists believe, the intensity of cosmic radiation must have risen at least by a factor of 30. This should have caused an increase of one order of magnitude in the natural background, which would at least double the mutation rate (and so the maximum rate of evolution) for the largest creatures on Earth. The effects could have persisted for more than 10,000 years.²⁰

Extraterrestrial creatures inhabiting a planet in the outer Core regions of the Galaxy should experience such a supernova event far more often — perhaps once every 10 million years. Over the course of geological history more than 500 local supernovae might occur. This would double mutation rates at regular intervals and keep the pace of evolution high — especially during the very early stages in the evolution of life on the planet when gene inventories were still small. We might hypothesize that species "turnover rates" may be significantly higher near Core regions than in the Disk of the Galaxy.

Many other factors may influence the rate of evolution on other worlds. For example, stellar class of the primary sun may be important. The hottest stars for which habitable planets are thought to exist are the F5 suns.

• These objects radiate more strongly in the blue part of the spectrum than our Sol, emitting about four times as much ultraviolet radiation.
• Because of this, many xenologists suspect that the early evolution of alien life on a world circling such a star should be considerably faster than on the primitive Earth.
• More energy could penetrate the oceanic surfaces, creating more complex nutrients faster and thus speeding the origin of life.
• F5 suns will also have stronger solar winds, which may lead to increased atmospheric ionization and greater climatic variability (and hasten evolution as well).

 
Higher UV levels near F5 stars may also delay the appearance of land plants.¹⁰¹³

• Since more of these rays must be filtered out by an ozone layer which necessarily must be thicker than Earth’s, sea plants of other worlds must wait longer than their cousins on Earth for the atmospheric oxygen content (which yields ozone) to build up.
• If the alien planet has small or shallow seas, then the total marine biomass may be too small. In such cases, oxygen would remain scarce, a sufficient ozone layer might never be built up, and land might never be colonized by plants.
• The larger the planet, however, the less likely is this catastrophe. All else being equal, larger planets have higher gravity and more compact atmospheres, which means a higher rate of ozone production.
• In either case, marine evolution should be comparatively rapid.

In contrast, K- and M-class stars peak in the red portion of the spectrum, emitting only 1-10% as much ultraviolet as Sol.

• This tremendous deficit should slow or greatly retard prebiotic evolution and the origin of life because less energy is available at the surface of the primitive planet for chemical synthesis.
• {tip content="Tidal locking (or captured rotation) occurs when
  the gravitational gradient makes one side of an
  astronomical body always face another, an effect
  known as synchronous rotation.
  For example, the same side of the Earth's Moon
  always faces the Earth. [from: Wikipedia]"}Tidal locking{/tip} is more likely in habitable zones around K- and M-stars; if locking occurs the environment could become quite severe (though relatively uniform), which will also tend to retard evolution.
• Finally, the UV deficit may forestall the dissipation of the primeval hydrogen/helium transsolar atmosphere. In such a system, even the innermost worlds might remain large, gaseous, and quite jovian.³⁷⁶ In this case, then, evolution may proceed more slowly.

 
Another factor which may quicken the pace of evolution is the presence of moons.

• By raising tides on the planetary shores, natural satellites may assist chemical mixing and catalysis during the early phases of prebiotic evolution in alien seas.
• Several xenologists have even suggested that mechanical wave motion may encourage and accelerate the invasion of the land by primitive plant and animal lifeforms.²³⁶²
• An interesting variation on this theme occurs when the alien planet is itself a moon — perhaps a super-jovian orbiter. While tidal locking will leave it a one-face world, the severely mutagenic radiations (such as exist near Jupiter) should provide ample genetic variation for selective forces to work with.

Planetary factors may also have a decisive effect on the rate of evolution. Perhaps the most influential of these is the relation between land mass distribution and the diversity of species — a part of the science of biogeography. Biogeographers have discovered what they call the Species-Area Rule.¹⁷¹³ Mathematically, the Rule may be stated as follows: S = kA^0.27, where S is the total number of species present in a land area of A square meters. (k is some constant, see below.)

In plain English, the Species-Area Rule says that, all else being equal, the number of different species present on any land mass is proportional to the area of that land mass. More land means more species; less land means fewer species. Thus, the rate of evolution is indirectly correlated with land area, since the production of more species requires "faster" evolution.

The Species-Area Rule has another interesting feature. It predicts that the same land area, fragmented into pieces, can support more total species than the original.

Take Earth as an example. If we assume there are 2 million animal species (a low estimate), distributed over 6 continents with a land area totalling 1.48 × 10¹⁴ meter², then the constant k = 80.7 for Earth. Now suppose that the continents were broken into 100 pieces. With a hundred separate island continents, having the same total land area as before, Earth theoretically could support as many as 15,600,000 species — more than a 7-fold increase.

Let’s try the Rule in the other direction. Today we have 6 continents and 450 taxonomic Families (such as the cat family, the dog family, the frog family, and so forth). But 225 million years ago there was only one global continent — Pangea — and only 146 Families. Using the Species-Area Rule, we would predict that Pangea could support 122 Families. By eliminating the modern continent of Antarctica (which is comparatively lifeless), the Rule predicts 139 Families, which is surprisingly good agreement with the paleontological data.

Why does the Rule work so well? One explanation is that the fragmentation of land masses provides a greater number of more heterogeneous environments for development. A variety of isolated habitats provides shelter from competition, and specialization may accelerate. The same land, linked together without barriers, permits competition and tends to eradicate specialized niches. Xenologists expect that the Species-Area Rule should be applicable in some general way to extraterrestrial ecologies located elsewhere in the Galaxy.

Another influential planetary factor is ecological complexity. Structurally complex habitats usually can support a wider diversity of species and thus a higher rate of evolution. This observation helps to explain the existence of "latitude gradients" in species diversity.²⁸⁶ That is, more species are found in equatorial tropical regions on Earth — where habitats are more plentiful — than in temperate or northern climes, where niches are comparatively few. Similarly, a fluctuating unstable environment favors the survival of "generalized", species with high adaptability (and presumably higher intelligence as well), whereas stable barrierless environments produce slower evolution and favor the survival of "specialized" species.¹⁷¹²

There are many other planetary factors which may affect the rate of evolution. For instance, smaller planets generally may have higher mutation rates because the levels of background radiation should be higher. There are various reasons for this.

• First, a diminutive world may experience less intense gravitational fractionation of rocky materials during its formation. Thus the proportion of heavy minerals (including radionuclides) should be higher in the crust.
• Also, and especially if it condensed in the solar nebula far from the central star, the planet may have a smaller metal-poor core and thus a weaker magnetic field.²⁸⁷⁶
• With less shielding from the solar wind, flares, and cosmic particles generally, the level of mutagenic radiation reaching the surface will be higher and evolution may proceed at an accelerated rate.²¹⁴

 
Another major factor that is often overlooked is planetary surface temperature.

• For any given biochemical basis, the reactions involved in life chemistry should proceed at faster rates on warm worlds than on colder ones.^{1132, 1171}
• But life processes also depend upon the complexity of molecular structures. As a general rule, chemical species are more stable and more complex at lower temperatures.⁷⁵
• Xenologists who have considered the problem believe that life of a given biochemical type will tend to evolve faster on hot worlds, but will be more complex on cold worlds.
• Presumably the faster evolution rate may be sufficient to compensate the lack of biochemical stability on hot planets, and vice versa.

Says astronomer Michael W. Ovenden:

On a planet near a star the potentialities of life are restricted, but those that exist are realized in a short time; on a planet a long way from its star, the potentialities are greater, but the rate of development and evolution is very much slower.⁷⁵

(Note: The effects of higher planetary surface pressure are biochemically similar to the aforementioned effects of elevated temperature.)

In addition to prebiotic and early biotic evolution, planetary temperature may also significantly affect the rate of evolution of macroscopic animal life. For example, consider a world where the emergence of life from the sea has been swift and warm-blooded species have evolved.

• A hot environment will selectively favor smaller lifeforms, whose high surface-to-volume ratio helps to slough off excess heat.
• Further, since the planet is hot, presumably more energy is available to drive the ecology (see below).
• More biomass can therefore be supported; since animals are generally smaller the total population will be large.
• Large populations can store more variability in the gene pool (all else being equal), and mutant traits are more likely to accumulate in single individuals. Hence, the rate of evolution should be somewhat faster.
• Finally, evolution should proceed even faster on large hot worlds, since the greater planetary surface area permits a bigger population to be sustained.²⁹

On the other hand, a generally cold environment should selectively favor larger lifeforms,⁶⁰³ whose low surface-to-volume ratio helps to retain body heat more effectively.

• Colder worlds should have less energetic ecologies, so less total biomass can be sustained.
• Since less biomass must be apportioned amongst generally larger creatures, the population should be small and evolution comparatively slow (especially on smaller worlds with reduced land areas).^{718, 440}

Change in gene frequency per generation Dq = v + q(s-v-u) - q²s,

• where q is the frequency with which the gene occurs in the original population,
• q + Dq is the gene frequency in the next generation,
• s is the gene’s selective advantage,
• v is the mutation rate favoring the gene,
• and u is the mutation rate opposing the gene.¹⁷⁰⁹

Subspecies often differ by only a single gene.

• The most reasonable choices are v = u = 10^-6 (unstable genes may have spontaneous mutation rates as low as 10^-2, but 10^-5-10^-6 is more usual)
• and s = 10^-3 (e.g., 0.1% more of those organisms possessing the new gene will survive than those without it).

If the frequency of the new gene is to increase from q = 1% up to q = 99% in the general population,

• about 9,200 generations will be required (about 10,000-100,000 years for most mammals.

Knowledge of the fundamentals of alien psychology is a "must" in any first contact or culture contact situation. No real comprehension of ET societies is possible without a thorough understanding of the differences between human and alien motivations, goals, and behavioral repertoires.

 
The field of xenopsychology is quite broad, encompassing issues of:

Unfortunately, it is beyond the scope of this book to deal with all of these fascinating areas in detail. Consequently the emphasis here will be upon the most immediately relevant basics.

We have already discovered that the environment is intimately involved in the process and rate of natural genetic evolution. Xenopsychologists, following modern sociobiologists, believe that a species’ surroundings also shape and direct the evolution of its gross behavioral patterns. Perhaps the single most critical environmental parameter is available bioenergy.

Table 20.2 Energy Flow at Various Trophic Levels in the Terrestrial Food Chain

The psychology of sentient extraterrestrials is closely intertwined with the details of the local ecology. But the most fundamental global ecological factor is energy. A more energetic environment normally can support either a larger number of similar-sized creatures or a similar number of larger-sized creatures. We know that all organisms require energy to survive, and that on most worlds virtually all of this must come from the local sun. In a sense, the star "feeds" the planetary inhabitants.

How much bioenergy is available to drive a global ecosystem? Clearly the first factors to consider are planet type and biochemistry type. Jovian planets and terrestrials will differ in the energy available to their native lifeforms. These planetological problems are dealt with in (Chapter 4) and (Chapter 5) in some detail, and will not be repeated here. Also, cold ammonia-solvent lifeforms may require less energy to maintain than a similar population of hot liquid-sulfur creatures.

But assuming a terrestrial Earthlike world and a biocarbon biota, we begin our analysis by noting that the total energy available at the top of the atmosphere should be about 2 × 10¹⁷ watts. About 90% of this is lost due to reflection, absorption and direct conversion to heat, or because it consists of unusable infrared radiation. The remaining 10% is available for photosynthesis — about 2 × 10¹⁶ watts.

Figure 20.1 The Energy Pyramid

The theoretical maximum efficiency for the chemical conversion of photon energy into organic matter (food) is about 36%.³²²⁰ However, the net observed efficiency of Earthly chlorophyllic plants generally runs from 1-5% in the field. The global average is even lower — about 0.2% — since the large open oceans are essentially lifeless aqueous deserts.⁴⁸ While other worlds may evolve more efficient photochemistries, or have a larger biologically active land area, it is doubtful that the 0.2% rating will be much improved by natural evolution alone. So, in the case of Earth, this leaves 4 × 10¹³ watts.

The energy pyramid (also "food chain" or "food web") shown in Table 20.2 illustrates how ecologies are powered by sunlight.³²²¹ At the base of the pyramid are the "primary producers" of food — on Earth, the green plants. These producers are eaten by "primary consumers," or herbivores. The herbivores, in turn, are eaten by carnivores, who themselves are eaten by still larger carnivores. Ecologists customarily refer to each successive stage of predation as a "trophic level." Thus plants are at the first trophic level, the smallest carnivores at the third trophic level, etc.

The Energy Pyramid (Figure 20.1) describes the flow of useful bioenergy through an ecological system. Plants are eaten by herbivores, which in turn are eaten by higher-level carnivores. Typical food chains have 3-5 stages, called ‘trophic levels." Only about 10% of the latent bioenergy in each level is passed along to the next — about 90% is wasted as heat or in respiration.

Omnivores, such as humans, may eat at all consumer levels. This permits larger populations to be supported. If men ate frogs instead of trout in the above example, 30 people could be supported. If he ate grasshoppers, 900 people could live. If he could consume grass, 2000 persons would survive.⁹⁹⁷

Figure 20.2 Illustrations of the Diversity-Stability Rule

Table 20.3 Maximum Supportable Large-Organism Population in a Typical Terrestrial Global Ecology (Earth)

Also, in ecology there is something called the Diversity-Stability Rule: Ecosystem stability tends to be correlated with food web complexity. The four equal-population food web structures shown in Figure 20.2 illustrate various possibilities. In (A), there are too few herbivores; in (B), too few carnivores. Predators and prey are too specialized in (C), which consists of simple linear food chains. Because of the multiplicity of intertrophic links in (D), it has the greatest potential for adaptive stability.²⁹⁷

Alpine and polar environments tend to have fewer links and less stability, while tropical and oceanic environments are generally more stable.

Experiments conducted in a wide range of different environments have measured ecological efficiency — the energy gained by an organism when it eats a member of the next lowest trophic level. A good rule of thumb is that at each level 90% of the available bioenergy is lost. Only 10%, on the average, is passed along to consumers at the next highest level. Due to the staggering amount of waste, few ecosystems on this planet have more than five trophic levels. Xenologists expect these generalizations to hold true for extraterrestrial ecologies as well.

As Table 20.3 demonstrates, the effects of limited bioenergy on size of population are striking. If all humans were purely herbivorous, Earth theoretically could support 50 billion of them. But if people tap into the food web as Level-5 carnivores (e.g., man eats trout, trout eat frogs, frogs eat grasshoppers, and grasshoppers eat grass), the terrestrial ecology could support only 50 million humans worldwide. If this happened, each person would have to patrol a home range (personally or by proxy) of about 10 km² in order to find his daily meal.*

Similar bioenergy assays may be made of smaller ecosystems, say, on the continental, regional, or local levels. But the conclusions are almost always the same: Herbivores maintain the highest population densities and the smallest home ranges, while carnivores are usually fewest in numbers and utilize the largest home ranges. Omnivores, who can tap into the food web at any trophic level beneath, fall somewhere in between. They are the most versatile and adaptive, and thus most likely to survive in both the best and worst of times.

Xenopsychologists are interested in these results for a number of reasons. The motives, instincts, and personality traits of a sentient ET are likely to be strongly influenced by its hereditary feeding habits.

An herbivorous race might be more socially-minded and less disposed to kill or commit acts of overt physical aggression. An intelligent carnivorous race might instinctively live in rather small groups, and value individuality and personal courage above all else.** A species with a large home range tends to be solitary and "antisocial."

Of equally great importance is the fundamental lesson of environmental finiteness. This turns out to be one of the central driving forces behind all animal and sentient behavior — whether psychological, social, or political. It is easy to see why this is so.

All lifeforms that dwell on planets, regardless of their shape, size, or biochemistry, must "consume negentropy" to live. This requires a flux of energy. But if biological order and information are to increase — a process which most xenologists regard as the basic "goal" of life — then energy flow through the total ecosystem must also increase.

But planetary bioenergy is strictly limited. The natural supply of usable energy will be in short supply on any world.

Scarcity is inevitable.

* The population density of human beings on Earth today ranges from:

• 0.0003 km²/person in Hong Kong to
• 1.0 km²/person in Mongolia,
• with a worldwide average of about 0.04 km²/person.
• Humanity, it would appear, is already herbivorous (trophic level 2, on global average).

** Except where large herbivores have evolved without an associated predator (e.g., elephants, 0.3 km²/animal¹⁷²⁵), carnivores are normally larger than herbivores because a predator must be more powerful than its prey. Larger bodies can support larger brains, and predation is a more active lifestyle than grazing and thus requires more alertness; xenologists expect carnivores to be more intelligent as a general rule. This conclusion has been tentatively confirmed by modern paleoneurologists.²⁹¹⁰

The sight of a stranger can provoke some of the strongest aggressive responses among Earthly animals. Wilson claims that the xenophobic reaction has been documented in almost every species showing a high form of social organization, vertebrates and invertebrates alike:

Male lions, normally the more lethargic adults of the prides, are jerked to attention and commence savage rounds of roaring when strange males come into view. And nothing in the day-to-day social life of an ant colony, no matter how stressful, activates the group like the introduction of a few alien workers.⁵⁶⁵

Competition and aggression are generally more intense within a species than between different species. Still, forced into close proximity, grossly different animals become nervous and uneasy — especially if the one bears a reasonable resemblance to an established fear-object (say, a predator) of the other. Zoologists sometimes attribute this to a kind of universal wariness between creatures differing substantially in physical appearance. Wilson admits: "In the primitive lexicon of the emotive centers, strange means dangerous."⁵⁶⁵ Adds another writer:

Interacting with a creature that is unfamiliar is anxiety-provoking. Its reactions, motivations, and desires cannot be assumed to be the same as one’s own, and therefore its behavior cannot be predicted. A movement that would not provoke anxiety when made by a friend or even a casual acquaintance can provoke an extreme response when made by a stranger. Given that situations involving unknown quantities are inherently anxiety provoking, it is relatively easy to understand how actions can be interpreted to mean something quite different from what the person who performed the act intended.²²²

Figure 20.3 Claw-Waving Threat Displays In Crabs Introduction Claw Waving Lateral Wave Additional    Introduction   Among humans, the open-fisted handwave is an almost universal sign of greeting. The handshake, perhaps a display of cultural origin intended to demonstrate a lack of offensive weapons, is similarly universal among human societies. So when a man sees the crab, he gives his favorite greeting. But consider the crab’s point of view. To it, claws are the main weapons of offense. The raising and lowering of claws, as well as any similar vertical or arclike waving motions, are characteristic threat gestures among many terrestrial crustacean species. To the intelligent crab, the human handwave may be interpreted as an invitation to attack, a sign that the man is of hostile intent and is asking for a fight.    Claw Waving Among crabs, claws arc the main weapons of defense and offense. Claw motions have been ritualized as characteristic threat displays. Above are the clawwaves of a variety of fiddler crabs, including: (a) Uca rhizophorae (vertical waving) (b) Uca annulipes (lateral waving) (c) Uca pugilator (circular wave with outstretched claw) (d) Dotilla blanford (double clawwave) (e) Goniopsis cruentata, or the mangrove crab (complex double clawwave)2827    Lateral Wave Above are a few more examples of fiddler crab waving. (a) The lateral-waving Fuji Island crab pulls its claw in initially (b) stretches it out in a sideways movement (c) raises it high above the head (d) then returns it along an arc to the original position Variations on vertical waving are shown in the sequences of: (e & f) the Malayan fiddler crab (g & h) the Philippine fiddler crab.2926    Additional Figure above – Lateral wave of Uca perplexa. (a) Four points used to define the three display stages: A - first movement of the claw B - end of the initial fast unflexing movement C - highest point reached by the claw tip D - end of the fast downward claw sweep (b) Elevation of five key body parts (illustrated in a) over time during a single       lateral wave. (c) Movements during the three stages of the lateral claw waving display: stage 1 - both the major and the minor claws are quickly unflexed stage 2 - the major claw is lifted slowly upwards and the body               and second ambulatory legs are raised stage 3 - the major claw, body and legs are rapidly dropped back                to resting position Figure 20.4 Releasers in Human Beings Brood care releasers Other releasers    Brood care releasers   Konrad Lorenz has suggested that behavior patterns of caring for young are released in humans by a number of cues which characterize infants. These "brood care releasers" include: Head large in proportion to the body. Protruding forehead large in proportion to rest of face. Large eyes below the midline of the total head. Short, thick extremities. Rounded body shape. Soft, elastic body surfaces, Round, protruding cheeks. Specific behavioral cues such as clumsiness. The figures above right illustrate the "baby schema" of human brood care behavior. In the leftmost drawings are head proportions of animal forms generally considered to be "cute". The rightmost drawings are the adult forms of the same animals, which do not release the drive to care for young.2922    Other releasers Lorenz also believes that humans have other releasers which affect attitudes towards other creatures. Above are shown the head of a camel (left) and an eagle (right). Lorenz claims that man has an innate releasing mechanism that responds to the relative position of the camel’s eyes and its nose. In man, this particular combination means "an arrogant turning away," so we consider the camel to be an aloof and arrogant animal. In the eagle the bony ridge above the eyes is viewed as a wrinkling of the forehead; together with the pulled-back corners of the mouth, the eagle’s expression is seen as "proud decisiveness" and daring. Unfortunately, these interpretations of the psychology of our fellow lifeforms have little or nothing to do with the actual mood of the particular animal involved.2925

Or, as yet another expresses it:

The mind of man is stocked to the gunwales with emotional parochialisms. Very few men would be self-controlled enough to extend courtesy to a horse-sized scorpion who was the master of another world, even if it were prudent to do so, even if the scorpion were venomless and exhibited the manners of a Spanish duke."¹⁵⁵⁰

Such gross physical differences may give rise to more subtle difficulties as well. Consider a meeting between a human being and an intelligent crablike creature. Among humans, the open-fisted handwave is an almost universal sign of greeting.²⁵⁵² The handshake, perhaps a display of cultural origin intended to demonstrate a lack of offensive weapons, is similarly universal among human societies. So when a man sees the crab, he gives his favorite greeting.

But consider the crab’s point of view. To it, claws are the main weapons of offense. The raising and lowering of claws, as well as any similar vertical or arclike waving motions, are characteristic threat gestures among many terrestrial crustacean species.²⁹²⁶ To the intelligent crab, the human handwave may be interpreted as an invitation to attack, a sign that the man is of hostile intent and is asking for a fight. The creature may oblige by attacking. Conversely, what if the crab is angry at us? Its clawwaving threat display might be interpreted by untutored humans as a friendly handwaving gesture of greeting. When the alien is approached peaceably, the ensuing attack by the mad crab may be regarded as treachery or slyness rather than a simple cultural difference between the two species (Figure 20.3).

Besides displays, a wide variety of behavioral "releasers" may render more difficult all attempts at cross-species communication and understanding, and make xenophobia more likely.^{2578, 2442} Again, one example will serve to make the point. According to Konrad Lorenz, human beings have a rather strong set of instinctual "brood care releasers" (Figure 20.4). Depending upon a variety of physical characteristics a lifeform possesses — large head, rounded body shape, short thick extremities, and so forth — people will find it to be "cute" and experience a strong desire to pick it up, cuddle and fondle it. This particular human releaser has been demonstrated repeatedly in various experimental situations.^{2923, 2924} Such feeling on our part toward the sentient aliens with whom we are dealing could result in behavior which is at best inappropriate and, at worst, fatal.

Xenopsychologists believe that xenophobic reactions cut across species, genus, and even phylum lines. Wariness of strangers is extremely common among the animals of Earth. So while we may be repulsed by the physical appearance of intelligent snakes, lobsters, and squid from other worlds, of one thing we may be almost certain: We will appear just as ugly to them.

Technology, or the artificial modification of the biosphere, is a unique method for achieving balance between population pressure and ecological forces.

• As suggested earlier, it may be used as a population reducing technique.
• However, the most important sociological function of technology is to increase production.
• This is of critical importance in alien social evolution.

Xenosociologists believe there are at least four fundamental requirements for the evolution of a technological civilization on a planet bustling with lifeforms:

1. Motivation or behavioral predisposition to use tools;
2. Manipulatory organs preadapted for tool-using;
3. Sufficient physical resources to build technology; and
4. Sufficient energy to power the technology.

High individual intelligence is not a fundamental requirement. Ants, bees, termites and other social insects have evolved technologies such as architecture, carpentry, dairy farming, and the domestication of other animals for "equestrian" purposes⁵⁶⁵ without advanced personal sentience. Great intelligence is certainly an enormous asset in the creation of a technical civilization, but it is not essential.

Early technological cultures may arise in any of three planetary environments:

• Telluric civilization (land)
• Aquatic civilization (sea)
• Avian civilization (air)

All human societies of which we are aware have been land-based. They also have all been found on Earth. How common are telluric civilizations throughout the rest of the Galaxy?

The first requirement is motivation.
On this planet — a typically exotic world — examples abound.

• Ant lions and worm lions knock insect prey into their capture pits by hurling sand with the head.
• Termites build structures on the order of 100 "stories" high, and ants maintain flocks of dairy aphids which are milked regularly.
• Beavers build dams and dome-shaped lodges.
• Primates display a wide variety of tool-using behavior — sticks are used for whips, clubs, spears, anthill fishing poles, toothbrushes, and as levers to pry open boxes, fruits, or nuts; leaves are used as drinking and feeding tools; and so forth.⁵⁶⁵
• Tool-using behavior seems widespread among land-living species on Earth

The second requirement (manipulators) is particularly easy, since ambulatory limbs which preadapt a species for tool-using are particularly suited to locomotion on land.

• Even the most primitive terrestrial vertebrate forms — the amphibians — have 5-fingered hands, two arms and two legs.
• Several species of lizards are known to have opposable thumbs, supposedly the hallmark of human tool manipulating ability.

• A few zoologists have speculated that if mankind were eradicated today it is likely that his technocultural replacement could evolve in as little as 15 million years.⁴⁰⁰
• The raccoon would be one possibility, since its hands are thought by some to be superior to our own for grasping and manipulating.
• Pandas have evolved an alternative but satisfactory method of grasping using a thumblike appendage, and koala bears have not one but two opposable digits on their forepaws.⁴⁵⁰
• Human related simian stock, such as chimpanzees and apes, might also replace us.

The third requirement is physical resources. As historian Richie Calder suggests, a technical culture can only manifest itself in the materials that are available from the physical environment:

The Eskimo, although an ingenious people and blessed with a remarkable memory, never developed beyond the Neolithic (New Stone Age) because of their very limited materials.. They had no access to ores that might have set them on the track of metallurgy; cold and snow prevented agriculture and made them hunters; they had no wood as they were beyond the tree line; and the lack of other plant life denied them fibers for weaving. Without these materials they simply were unable to evolve their own technology.⁹⁶⁸

Discussions among xenologists on the availability of technology materials frequently center upon the abundance of various metals on planetary surfaces. (See Bova,¹⁴⁰⁰ Huntington and Cushing,²⁶²⁰ and Livesay.²⁷²³)  Astronomical aspects are best considered first. For instance:

• Most Disk stars in the Galaxy should have sufficient metallicity to permit terrestrial planetary formation provided other conditions are also favorable.
• Core stars generally have even higher metallicity, so the physical resource factor is even more positive for the evolution of metal-using technical civilizations.
• Also, the older a star the sooner it was formed from the primordial galactic nebula — and thus the fewer heavy elements it and its worlds may possess.²⁸⁷⁶

Planets located in mid-habitable zone (of the biocarbon ecosphere) normally will show heavy element compositions roughly similar to Earth, having condensed out of the primitive solar nebula at about the same temperature.²⁰⁵⁰ While the total fraction of heavy elements varies from star to star, the relative fraction of each metal is surprisingly uniform.¹⁹⁴⁵

While planetary bulk composition may stay relatively constant (in a given ecosphere around the star), there may be serious problems in surface distribution. As suggested in an earlier chapter (Tooltip text), large worlds should have thinner crusts (which more easily buckle) and more severe tectonic activity. This activity will tend to thrust rich subcrustal heavy metal deposits to the surface, making them available for technological utilization. (Prospectors have long known that the richest mineral and ore deposits are generally found in regions of volcanic activity and in mountainous terrain.²⁹⁰⁹) Less-massive planets should have comparatively few concentrated ore deposits near the surface.

The fourth requirement for civilization is energy.
Land dwellers are pretty well-off.

• Fibrous vegetation or animal oils can be burned, as can natural hydrocarbons tapped from pools or pockets of decaying organic matter.
• Fires permit smelters and the working of metal products, and the technology is on its way.*

* There may be a few unusual (to us) cases. For example, on a planet with a chlorine atmosphere heavy metals might serve as fuel. In Cl₂ gas, hot strips or wires of copper, or iron wool, spontaneously burst into flames.

Many possible variants of aquatic civilization have been named by xenosociologists.

• Amphibious littoral civilizations, for instance, may inhabit the seashore.
• Pelagic civilizations would occupy the water mass and the surface of the sea.
• Benthic or abyssal civilizations may live in the extreme ocean depths and sea floor of other worlds.
• Estuarial civilizations may make their homes in bays, fiords and river waters.
• Limnic cultures could live in lakes.

But are aquatic technical civilizations possible at all? There has been much written on this point, and most writers seem to have reached a negative conclusion. (See Anderson,⁶³ Hoyle,¹⁵⁵⁹ Livesay,²⁷²³ MacGowan and Ordway,⁶⁰⁰ Macvey,⁴⁹ and Strong.⁵⁰)  But this author believes the majority is wrong.

Consider the requirement of motivation.
Many water-dwelling lifeforms on Earth employ technologies (e.g., artifacts) to assist in their survival.

• One of the most primitive is the archer fish (Toxotes jaculatrix), which carefully aims and spits blobs of water at its prey (insects and spiders) to knock them into the water where they can be caught in the fish’s mouth.
• Another example, considerably more sophisticated, is the octopus. This intelligent invertebrate gathers stones, chips, and metal scraps to build small cavelike houses in which it resides.
• Another unusual example is the sea otter (Enhydra lutris). This semiaquatic mammal collects stones and shells from the ocean bottom. Then, while floating on its back at the surface, the otter places these objects on its stomach and uses them as anvils against which to pound and crack open mussels and other hard-shelled molluscs.⁵⁶⁵

It appears that many sea creatures on this planet are strongly motivated to try their luck at technology. If Earth is typically exotic, water worlds elsewhere in the Galaxy should fare no worse.

What about manipulators? The lack of manipulative organs in the most intelligent seagoing animals — the cetaceans — implies that their intelligence "cannot be worked out in technology,"^{1365, 15} unless they have outside help. But this may just be an evolutionary fluke. Elephants seals, a genus of "returned mammals" closely related to the cetaceans, still retain the incredibly delicate, 5-digit "flipper fingers" that their cousins the dolphins must once have possessed. On another world, brains and hands may coincide.*

Of course, there is no reason why boneless tentacles could not serve as technologically useful appendages in the absence of hands and fingers. The cephalopods, which include the octopus, cuttlefish and squid, have from 8-10 limbs surrounding their mouths. These probably evolved from whiskerlike projections near the food cavities of more ancient molluscan forms. The fact that intelligent octopoids do not dominate the seas of Earth may be, again, merely an evolutionary fluke. First, octopuses have hemocyanin blood, which is less efficient than hemoglobin. The animal tires easily and has little appetite for sustained heavy labor. Second, octopuses have ganglionic nervous systems which may have limited their sentience on Earth. But there is nothing fundamentally wrong with a tentacular intelligence. The convergence with certain well-known land forms (prehensile-tailed monkeys, elephants) strongly suggests that tentacles may build technologies on other worlds.

How about physical resources?

• Clays and mud are available for ceramics and pottery, sand for glass, and there is a tremendous variety of organic materials available for chemical industry — dyes, acids, drugs, etc.
• Stone masonry is quite possible, since concrete can be mixed that can set underwater. Nodules littering the continental shelves and ocean floors could be harvested for their nickel, cobalt and manganese.
• Fantastic quantities of metals are afloat in seawater itself. For example, a kilogram of iron can be harvested by filtering 50,000 m³ of ordinary seawater past a simple magnetic lodestone. (The liquid volume involved is only about as much as a single shark breathes in a month.)
• Marine lifeforms could devise an advanced biological technology including "cold light" streetlamps using luminiferous bacteria, architectural coral, and "slave fishes."

Where do we get the energy to work all these resources?

• Aquatic ETs may discover superheated underwater volcanoes — these exist in great numbers on Earth’s ocean floors and should be even more numerous on larger, more massive pelagic worlds.
• Submarine oil deposits may be found in sedimentary strata. Natural gas and other combustible vapors upwelling from the planetary interior could be trapped in special containers and burned using oxygen imported from the surface.
• Lacking combustion, bubblewheels could be erected over regions of submarine helium gas effluence and the rotary power used to turn mechanical flywheels.

There is no bar to the full development of electrical power generation.

• Electric eels could be domesticated for this purpose, or simply cannibalized for their organic batteries.
• Alternatively, marine extraterrestrials could build their own batteries using pieces of carbon, tankards of seawater and some other electrolyte, and a small bit of metal.
• The electricity thus obtained might then be used to perform electrolysis on water, splitting each molecule into its constituent hydrogen and oxygen atoms.
• This gaseous mixture is a potent fuel, and could conceivably be used to power smelters, streetlights, seacars and seabuses, 2800 °C oxyhydrogen blowtorches, turbines and jet-propelled devices, and even rockets.

There is little that man has accomplished technologically on land that could not be repeated in some analogous fashion by a race of marine lifeforms on a pelagic world elsewhere in our Galaxy.

* It is interesting to note that cetacean intelligence soared following its return to the sea, reaching a level of "encephalization" equal to that of modern-day humans 10 million years ago.²⁹¹⁰ There is no truth to the assertion that the sea is incapable of bringing forth high intelligence, for it was the seagoing dolphins, not humans, who first made it to the top. Ethologist John Eisenberg correctly points out that the assumption that the marine environment is homogeneous is false: "There are currents and different temperature and pressure regimes which make it very exciting."³²⁴¹

Almost without exception, previous writers have concluded that technological civilization among avian creatures is virtually impossible. (See Hoyle,¹⁵⁵⁹ MacGowan and Ordway,⁶⁰⁰ and Strong.⁵⁰) Again, the author strongly disputes this conclusion.

First of all, aerial lifeforms on Earth appear favorably disposed to tool-using.

• Solitary wasps (Ammophila) pound their nest entrances shut with a small pebble held in their mandibles.
• The woodpecker finch uses twigs, cactus spines and leaf stems to dig insects out of crevasses in tree bark.
• The Australian black-breasted buzzard carries rocks and lumps of soil skyward; released, the rocks fall on the eggs of other birds which break and are eaten by the buzzard.

• The black cockatoo of the Aru Islands grasps nuts in its beak with a leaf while cracking them open (like holding a jar in a towel for better traction while the lid is twisted off).
• And northern blue jays, held in captivity, have been observed tearing off strips of newspaper flooring and using them to rake in food pellets placed out of reach beyond the mesh wall of the cage.⁵⁶⁵

Extraterrestrial creatures evolving in similar aerial niches may be expected to develop similar biological predispositions.

How about manipulative appendages?

• Several writers have argued that when birds evolved wings they lost the use of one of their two pairs of limbs.
• Thus they cannot have arms or hands to work out their intelligence in technology, and so there can be no technical civilization of the air.
• But this line of reasoning overlooks the possibility that the ancestral form of alien avians might be, say, hexapodal.
• If the original reptilian stock had begun with six legs instead in four, then two could evolve into wings, two into arms, and two could remain legs.
• Alternatively, the "gasbag beasts" described in an earlier (chapter) would most likely feed from the underside, and so might evolve mouth-tentacles much like the cephalopods of Earth’s seas.

Such limbs would admirably fulfill the requirement of a manipulatory organ and should permit the emergence of an ET avian technological civilization.³²³⁴

As for materials and energy, resources on the ground will probably have to be tapped because the air is practically devoid of useful minerals. Wind power and rain power are possibilities, but fire is probably much easier and will directly permit the smelting of structural and ornamental metals. Avian technology should be very similar to telluric technology generally. It is also possible that tool-using avians may be land-dwelling "returned" lifeforms, adapted to a permanently flightless existence much like the ostrich, the kiwi, and the extinct giant moa (a bipedal, bimanous 240 kg bird) of Earth.³⁰⁰⁶

In his recent book On Human Nature,³¹⁹⁸ sociobiologist E.O. Wilson suggests that human social behavior is best evaluated by comparison with the behavior of other major categories of Earthly species.³⁶⁴⁶ Human beings are proud of their intelligence and many cultural achievements, but seldom do they pause to consider how many of their social traits can be traced back to their primate (and mammalian) ancestry. Remarks Wilson: "The general traits of human nature appear limited and idiosyncratic when placed against the backdrop of all other living species."³¹⁹⁸ Or, as Clarence Day pointed out many years ago in his lighthearted essay "This Simian World,"⁷⁶ many of the strategies people use to cope with the environment are characteristic of our arboreal, visually-oriented, curious, manipulative, leadership-hungry, pair-bonding, verbally communicative simian forebears. Psychologically as well as physiologically, humans have a lot of monkey in them.

Wilson gives several examples.

• Intimate social groupings among humans usually contain on the order of 10-100 adults, never just two (as in most birds and marmosets) or up to thousands (as in many fishes and insects).
• Human males are generally larger than females, the result of a mild form of sexual competition common to primates and many other kinds of mammals.
• The young are psychologically molded by a lengthy period of social training, first by close associations with the mother and later by interaction with other children of the same age and sex.
• Another common feature is social play, a strongly developed activity involving role practice, mock aggression, sex practice, and exploration.

These and many other properties together identify a constellation of social traits characteristic of the taxonomic group including the Old World monkeys, the great apes, and human beings. Notes Wilson:

It is inconceivable that human beings could be socialized into the radically different repertoires of other groups such as fishes, birds, antelopes, or rodents. Human beings might self-consciously imitate such arrangements, but it would be a fiction played out on a stage, would run counter to deep emotional responses and have no chance of persisting through as much as a single generation. To adopt with serious intent, even in broad outline, the social system of a nonprimate species would be insanity in the literal sense. Personalities would quickly dissolve, relationships disintegrate, and reproduction cease.³¹⁹⁸

An exhaustive inventory of the elements of "human nature" has yet to be prepared. However, a few partial lists have been compiled.
In 1945 the American anthropologist George P. Murdock listed³²⁰¹ the following root characteristics of man’s society which have been recorded virtually in every human culture known to Earthly ethnographers:

After citing Murdock’s work, Wilson suggests that few if any of these properties are inevitable outcomes of either high intelligence or advanced social life; "human nature is just one hodgepodge out of many conceivable."³¹⁹⁸ An entomologist by training, Wilson has no trouble imagining a nonhuman insectlike society whose members are even more intelligent and complexly organized than people, yet which lacks many of the qualities listed in Murdock’s inventory above. The "alien" inventory might look something like this:

…and still other activities so alien as to make mere description by our language difficult.³¹⁹⁸

Civilization, says Wilson, is not intrinsically limited to hominoids. Only by an accident of evolution on this particular planet was it linked to the anatomy of bare-skinned, bipedal mammals and the peculiar qualities of human nature.