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Origin and DevelopmentEdit

Technological development is a very effective way to maximize population, and therefore evolutionary success, over adverse circumstances. Once a sapient species is established on a planet, presuming that it has the physical capability of manipulating tools, it will probably start to bend the environment to its advantage, extracting energy, building instruments and shelters and breeding wild species.

Environment and TechnologyEdit

Also see here and following pages.

While simple tools can be found or made in every environment, a technology as complex as humans' requires the presence (in fact, the abundance) of natural resources to build instruments, weapons, vehicles, buildings and machines. A sterile territory can irreparably stop the development of a civilization: the barren Arctic land denied to the Inuit people timber, farmland and accessible minerals.

Inorganic mineral resources (stone, sand, clay, metals, obsidian, ice, salt, lime, mineral dyes) should exist on any rocky planet, and so should their derivatives (glass, terracotta, concrete). Metals have a key role: they're uniquely malleable and conductive to heat and electricity, so much that an advanced technological civilization isn't likely to exist without an extensive use of metals. It's still possible, of course, to have a complex civilization: Mayas had large cities, figurative art and elaborate writing, advanced math and astronomy, etc., all without using metals except for decorative gold. Anyway, presuming a planet rich in heavy elements in the galactic disk, metals should be abundant, especially if the planet has weak gravity or a strong tectonic activity.

Smelting metals requires a powerful and localized source of heat up to several thousands of degrees, such as fire (see below), which in turn requires the direct access to oxidants: it's therefore impossible to smelt metals underwater (or inside any other thalassogen, or in a strongly reducing atmosphere, rich for example in hydrogen compounds), though it could be possible to work to a certain extent softer metals such as gold, copper and lead. Even if other heat sources could be found in an ocean, for example hydrothermal vents, water is too conductive to heat to allow any oceanic blacksmith to get close to them. Metals could be used to cover other objects through electroplating, if electricity is harvested from organisms similar to electric fish and the thalassogen has a high dielectric constant (see the table here).

Other resources (wood, bark, bone, horn, ivory, wax, leather, silk, byssus, purple, coral, etc.) are a part or a byproduct of organisms: it will directly depend from the biochemistry and ecology of the species from which they're collected.

Farming and BreedingEdit

The availability of plants and animals (or whatever their extraterrestrial analogue is) apt to domestication has a huge weight on the development of civilizations. Plants are almost always grown for food (except for some textile plants such as flax and cotton): they're usually selected, at least on Earth, for large and nourishing seeds. Areas with a mediterranean climate, with strong seasonal variations, are the most apt, since the plants that inhabit them often live only one year and thus spend all their energy for reproduction, instead of expanding their own body with structural, and usually inedible, matter.
File:Origin and spread of agriculture.png

Agriculture will be encouraged in wide arid lands with fertile but very small areas useful to grow crops, such as a river valley (e. g., Nile, Euphrates, Mississippi); if the land is too plentiful, its inhabitants will be able to live there as hunters-gatherers for much longer, as it happened in early Japan. These areas both arid and fertile will likely appear in the belt between the Ferrel and Hadley cells. While agriculture won't likely appear soon near tropical forests, it may be imported and adapted there with forms such as the shifting cultivation (small tracts of land are briefly farmed and then abandoned) and the slash-and-burn (parts of forest are destroyed to gain access to the enriched soil).

Animals can be breeded for a variety of purposes:

Function Examples
Food (meat) Cattle, sheep, goat, rabbit, pig, chicken, guinea-fowl, turkey
Food (production) Cattle, sheep, reindeer, goat, yak (milk); chicken, goose, quail (eggs); bee (honey)
Burden, work Cattle, horse, donkey, dog, camel, llama, indian elephant, reindeer, yak
Materials Sheep, goat, alpaca (wool); silkworm (silk); cattle (leather); fox, mink, chinchilla (fur)
Help with hunt Dog, ferret, falcon
Pest control Cat

In Guns, Germs and Steel, Diamond lists six main factors needed for the full domestication of an animal:

  • It has to be herbivorous or omnivorous, with a varied diet, since the meat that a carnivore has to be fed requires in turn a ten times larger amount of plants for its production: it's far more effective use directly the plants as food. In fact, the only domestic carnivores on Earth are those who partake in hunting or sustain themselves by eating parasites.
  • It has to grow quickly reaching the adult size in a few years: this excludes gorillas and elephants (indian elephants are not domestic, only tamed: they're captured when they're already grown).
  • It has to reproduce easily in captivity: this excludes, for example, vicuñas and leopards.
  • It must not be much aggressive: this excludes grizzly bears (otherwise omnivores easy to feed and quick to grow), buffalos, zebras and rhinoceroses.
  • It must not have an inclination to panic: this excludes gazelles, which are extremely hard to contain.
  • It has to have a hierarchic social structure in which the breeder can take part: this excludes bighorn sheep and deer (with the exception of reindeer), which are social but don't follow a leader as sheep and horses do. The only non-social species ever domesticated are cats and ferrets, none of which are bred in large numbers.

Probably, animal breeding will be more attractive in areas where there is less diversity of large animals: in Africa, where large-sized mammals had more time to adapt to human presence and thus suffered less from human-induced extinctions, hunters could always move to a new prey if the older one became unavailable, while Eurasian people had to choose a handful of critical species to look after. Farming and breeding will probably arise and spread faster on continents with a wide orizontal orientation (e.g. Eurasia), since they contain long parallel belts of similar climate, allowing an easier diffusion of domesticated specie from a place to another, while vertically oriented continents (e.g. the Americas) or islands (e.g. New Guinea) are not likely to spread or trade successfully species.

Energy SourcesEdit

The most common and primitive source of energy that any early civilisation will have at its disposal is musclepower, both that of the sapient themselves and of beasts of burden, fueled in turn by food.

Combustion is another simple way to extract energy from matter: it involves chemical reagents combining in presence of a strong oxidiser, releasing heat. This is also what happens in cells when digesting food. Fire is a particularly quick form of combustion, which produces very intense and focused heat, necessary for many processes such as cooking food, baking clay into terracotta and smelting metals (see above). While combustion can occur with different oxidisers, true fire on a large scale requires oxygen: fluorine gas could be used, while copper or iron can burn when exposed to chlorine, but both of these are very unlikely to exist in large amounts.

A carbon-based biochemistry can produce great amount of fossil coal and hydrocarbons (such as oil and methane), excellent fuels; oils and fats can be burned as well as digested, and so can sugar, especially when fermented into alcohol. Hydrogen, which can be produced biologically by splitting water molecules, is an even better fuel: when it burns with oxygen, forming water again, it can produce three times more energy than oil. Notice, however, that the artificial production of any fuel will require the same energy that will be extracted from it.

Nuclear reactions include fission and fusion. Fission involves splitting atoms of heavy and unstable elements, such as uranium; like metals, this elements will be more common in planets with a weak gravity or a strong tectonic activity, so that they won't sink to the nucleus. Fusion involves instead fusing hydrogen atoms in heavier elements: it's harder to control (in fact, controlled nuclear fusion has never been achieved by humans) but it's far more effective, and hydrogen can be easily obtained by electrolysis of water or other molecules.

While antimatter offers the most efficient mass-to-energy conversion possible (by annihilating itself with an equivalent mass of regular matter) it's very unlikely to be found in significative amounts in the Universe. Its synthesis, of course, would require the same amount of energy that it will produce: antimatter would therefore be an efficient, if impractical, way to stockpile energy, but not a good source of it.

Efficiency of various energy sources[1]
Energy source Fraction of mass converted in energy Energy production (J/kg)
Chemical combustion (including metabolism)
Nitroglycerine 0.000 000 007% (0.07 ppb) 6.3×106
Sugar 0.000 000 019% (0.19 ppb) 1.7×107
Wood, lignite 0.000 000 021% (0.21 ppb) 1.9×107
Alcohol 0.000 000 032% (0.32 ppb) 2.9×107
Coal (anthracite) 0.000 000 036% (0.36 ppb) 3.2×107
Fat 0.000 000 043% (0.43 ppb) 3.8×107
Crude oil 0.000 000 052% (0.52 ppb) 4.6×107
Methane 0.000 000 064% (0.64 ppb) 5.7×107
Gasoline 0.000 000 090% (0.90 ppb) 8.0×107
Hydrogen 0.000 000 160% (1.60 ppb) 1.4×108
Nuclear fission
Uranium-235 0.085% (850 000 ppb) 7.7×1013
Nuclear fusion
Hydrogen → helium 0.7% 6.3×1014
Hydrogen → iron 0.9% 8.3×1014
Antimatter 100% 9.0×1016

Solar energy can be directly intercepted and used as heat or converted into electricity through photovoltaic cells. On Earth, each square meter receives in average 1.6×107 J of solar energy per day. Remember that the solar irradiation is directly proportional to the luminosity of the star and inversely proportional to the square of the distance, though a thin or thick atmosphere might further increase or reduce this value; the best current photovoltaic cells have an efficiency of 14-17% (they need roughly 6-7 joules of solar light for each joule of electricity produced).

It can also be used indirectly, as wind or hydric energy. Wind energy can be directly converted in rotatory motion, and this in electricity by turbine generators (low-altitude wind flows from colder to warmer areas; see here). The same can be said for hydroelectric power (which is usually obtained thanks to gravity), and for the energy of sea currents, likely analogues of wind power for aquatic civilizations. Tidal power involves turbines put in motion by the vertical flow of water during tides; of course, it requires the presence of a large and near celestial body.

Geothermic energy involves extracting heat from the interior of the planet, usually in volcanic areas: it'd be more efficient on a planet with strong tectonic activity. Geothermic, nuclear and heat solar energy all can be used to produce electricity simply by heating water and using the steam to power a turbine generator.

Approximate efficiency of energy converters[2]
Energy converter Efficiency (fraction of energy successfully converted)
Solar cell 10%
Animal muscle 25%
Gasoline engine 30%
Diesel engine 38%
Steam power plant 40%
Steam turbine 45%
Hydrogen fuel cell 60%
Small electric motor 65%
Large electric motor 90%
Synchronous electric generator 95%


The historical and geographical features of a region affect its wealth and prosperity in several ways[3]. For example, a long history of stable government (China has been stable and unified for most of the last 3000 years) promotes further stability, aided by supportive ideologies, a (ethnically, culturally, etc.) homogeneous population and few natural barriers. Other political factors that help economic development are high education, advanced technology and inclusive political institutions.
File:GDP PPP Per Capita IMF 2008.png

Coasts and rivers favour trade; landlocked countries end up poorer than others. If the climatic structure resembles that on Earth, temperate and sub-polar regions will probably be richer than tropical ones because of two factors:

  • Since the high temperature and moisture allow parasites to survive outside a host body, and the higher tropical biodiversity offers a wider range of vectors (ticks, mosquitoes, etc.), the tropical belt is more subjected to infective diseases, severely limiting the population. Also, the need for high fertility will force most of the offspring-caring individuals to nurse continuously, keeping them out of the workforce.
  • Agricultural yields (see above) suffer because tropical plants typically invest their energy for growth, and thus in inedible structural matter, and because the higher rainfall and decomposition rate cause the ground to be poorer both in minerals and organic chemicals. Rainfall is also more predictable at higher latitudes, and glaciers enrich the soil in nutrients.

The abundance of mineral resources, such as oil and diamonds, is not guaranteed to bring prosperity; in fact, it's more likely to cause corruption and low education (most of the economy is going to be based on resource mining). If a colonial history is present, resource-rich regions with dense population, such as India, are likely to be exploited through forced labor and confiscation, and thus to end up impoverished; resource-poor regions with sparse population, such as Australia, will be forced to invest on productivity and education. This difference will be meaningful long after colonialism will have ended.


Among the several methods devised by mankind to acquire knowledge, the scientific method (the formulation of an hypothesis to explain observations, followed by experiments to test the prediction based on this hypothesis) has been uniquely effective in the development of both theoretical knowledge and technology. Until a civilization employs scientific thinking, it's unlikely to produce technology more complex than basic machinery (such as clockwork and windmills, which already existed in the late Middle Ages).

Science is a result of many combined lines of thought: the rationalism of greek philosophers (that is, the belief that knowledge can be obtained through logical thinking); the abrahamic idea of a lawmaker god clearly distinct by lawmaking humans, leading to that of a Universe ruled by given laws independent from man (developed in proto-science in the early islamic civilization); the concept of self-interpretation and rejection of authority as a basis of knowledge, spread with the Protestant Reformation; empyrical inductivism, matured in the 17th and 18th-century Europe.

Given this, not every sapient species has to develop science, and certainly many civilizations won't. Those who do are likely to be civilizations with an early technological headstart (see for example the conditions for successful agriculture) and in close contact with several other different civilizations.

Culture and PsychologyEdit

Besides its material features, a civilization will have a multitude of non-inherited behaviours, values and beliefs, with all the symbols and customs that give them significance, which will influence the way it sees the world, and that are in turn influenced by biology and environment. Human culture displays a huge variety, though there always are common traits called cultural universals (e.g. personal names, law, kin groups, age and prestige status, gender roles, marriage, prohibition of incest, metaphoric language, measuring of time, magical thinking, attempts to control nature, myths, music, body adornment, cooking, weapons, shelters, etc.)

It's not at all easy, anyway, to understand what a inhuman culture might be like. For example, in an ermaphroditic species there would be no place for gender roles, while parthenogenetic species with little or no genetic mixing could have no qualms about incest. What would these beings value? What would they like? What would they believe?

In the 1940s, the anthropologists Kluckhohn and Strodbeck wrote a summary of the main ethical and spiritual values in the form of possible answers to common philosophical questions, which can be combined in any way by a culture (answers in the same column bear no relation to each other)[4]:

Question Answer #1 Answer #2 Answer #3
What is the basic nature of people? Evil. People can't be trusted and need a strong control. Mixed. There is both good and evil in people. Good. Most people are good, except for social conditioning.
What is the best relationship with Nature (Fate, God, etc.)? Subordinate to Nature. What happens was meant to happen: there is no way to modify life. Harmonic with Nature. People exist as a part of Nature. Dominant over Nature. Conquering and controlling Nature is a challenge to be overcome.
What is the most important time? Past. People should learn from history and preserve traditions. Present. There is no point in bothering with past or future; there's only the present. Future. A careful planning brings the best future, even with some sacrifices in the present.
What is the best mode of activity? Being. It's not necessary to accomplish great things: living well is worthwhile enough. Becoming. The greatest goal in life is changing and developing oneself. Doing. Worth is measured by accomplishments, which come from work and perseverance.
What is the best form of society? Hierarchical. There is a natural order in society: some people should decide, others obey. Collateral. Everyone in a group should have a share of benefits and responsabilities. Individual. What matters most is that everyone has rights and is free to control one's own destiny.

The topography and climate of the environment will also have heavy repercussions on the culture, the degree of dispersion, the objects of worship, etc. of a culture. At the simplest level, one might imagine "ocean cultures" (Minoan and Polynesian people), "mountain cultures" (Incas and Tibetans), "river cultures" (Egyptians and early Chinese), "desert cultures" (Tuareg and Israelites), "forest cultures" (Indians and Amazon people), "grassland people" (Mongols and Comanche) and so on.

Social OrganizationEdit

We'll take for granted that some form of society is necessary for the development of a complex culture and therefore technological advancement. Primates, elephants and cetaceans all live in compact group based on kinship, and they're able to communicate and feel empathy; particularly, primate societies are already large, hierarchical and highly politicized by rivalries and alliances between individuals. Empathy - the perception of the similarity between oneself and others, leading to selfless cooperation and limitation on violence - can be expected to arise in any social species, especially if they live in small and/or viscous populations.

Generally, empathy is stronger the closer is the group: baboon and chimpanzee societies are violently xenophobic towards other. Xenophoby would likely be exacerbated by evident polimorphisms in various populations ("races"). Among humans, the natural aggressivity is channeled into war between societies, sometimes in bloodless ritualized forms such as agonistic sport. Usually, the stronger individuals (young males in primates) will be used for this purpose, but Solenopsis ants use as soldiers the oldest ones.

In primates, males are usually larger than females, thus leading to a general male dominance in most human societies, but among elephants and many cetaceans the opposite would happen. Then there's the case of multiple-gendered or ermaphroditic species; with sequential ermaphroditism (a sex changing into another with age) the dominant sex would probably be the final one. In this case the formation of lifelong familiar bonds could be impossible. Marriage is among the most universal institutions in human societies: each new individual has to be raised and taught for many years by several older ones in order to pass on culture. Human monogamy is a relatively new social construct that doesn't always fit with primates' typical promiscuity, but most birds are truly monogamous by nature.

Xenology gives some examples of terran animals that might be used as models to build extraterrestrial societies[5]:

  • Mammalian groups tend to be centred on the mother-child bond, and therefore on matriarchal structures, with some exceptions. Lion prides, for example, are formed by groups of females with a male (or male brothers) and the cubs; similarly, black bears society are based on solitary mothers that sometimes share their territory with the daughters, while males always hunt alone.
  • Among carnivores, play, prey-catching and aggressivity are especially developed; cats are usually solitary and fiercely territorial, with extreme uneasiness and irritability when enclosed together.
  • Canids such as wild dogs and wolves hunt in packs of several tens of individuals; these packs are highly cooperative and altruistic, with equalitary partition of food and feeding priority given to infants - despite strict dominance hierarchies and violent population control.
  • Wallabies, though strongly individualistic, graze in large mobs (30-50 individuals) that often meet and meld peacefully; aggression is ritualized and rarely dangerous.
  • Beavers live in "cities" inhabited by several families; population is very stable, with low birth and death rates. Different families often work together to build the dams, but each family will defend its lodge from other ones.
  • Prairies dogs live in underground towns with up to a thousand individuals each, divided from other cities by natural boundaries. Each family has its own territory inside the town, which gets passed on culturally.
  • Birds are less promiscuous than most mammals, and more incline to strong pair-bonding, with a heavy involvement of the male in offspring care (after all, newborn birds are not nursed, and eggs can be brooded by either parent).
  • Social spiders live in colonies with thousands of individuals, working together to build a common web, and to capture large preys; otherwise, each spider lives for himself, and injured spiders - or those who lack the colony scent - are devoured by the others.

Logic and SpacetimeEdit

Also see: here, here and following pages.

The psychology (and therefore the knowledge, and the philosophy) of a sapient species will also be strongly influenced by the way it perceives the world through senses: for example, the persistence in time of heat and scents might create a perception of time without a clear distinction between past and present - and language will reflect this lack. After all, many human languages show a great variation in this regard: Hopi language does not have verb tenses that express time, while many others have tenses to distinguish past events that influence present from those that don't.

The perception of time might also be expanded or contracted by the speed of nervous reactions or of the metabolic cycle; perhaps a blue whale, with a heartrate three times slower than a human's, perceives time three times faster. Astronomical (days, years, months, seasons, tides) and biological (generations, periodical migrations, spring blooms, menstruations) cycles will influence more directly the measurement of cultural time.

The understanding of space is even more variable. Depth perception, developed to live in the three-dimensional environment of treetops, allows humans to conceive spatial geometry; wide and flat areas favour instead Euclidean geometry (developed by Egyptians to measure farmland). On a very small planet, a flat environment would be conductive to spherical geometry, by stressing the horizon bending.

A cave-dwelling sapient, or an internal parasite (extremely unlikely case), used to a limited environment, might lack the concept of infinite (and perhaps it would develop hyperbolic geometry, based on surfaces with a negative curvature); a very small one, in a very dense fluid medium, and/or on a world with a weak gravity, might be unable to distinguish top from bottom; one that sees the world with electric or magnetic senses might base its geometry on curved field lines.

Spacial perception also has major psychological and cultural implications: since the main human sense organs are located in the upper part of the body, what is high is "superior", virtuous and active (one stands up to act and lies down to rest), and what is low is "inferior", depraved and passive; the right hand is the dominant hand for most people (70-90%), so it's used for the most important tasks: right is the side of strength and cleanliness, and thus of law and morality; the front is dynamic and future-oriented, the back is passive and past-oriented. In many language, the future is "forward", and the past "backward", because time is commonly represented as a path; but in the Quechua language the future lies behind, because it's unseen.

While the principles of logic and math are universal, their representation can vary too: while Aristotle identified as truth values only "true" and "false", buddhist philosophy recognises four values ("true", "false", "both" and "neither"), jainism seven (various combinations of "true", "false" and "indeterminate"); modern logic admits intermediate truth values, a development that could be easier for sapients that perceive the world through blended gradients of scent and heat. It could be that the prevalence of binary logic in human thought is connected to our bilateral (two-sided) simmetry: Parasky's priapans have a radially symmetric body, and don't see opposite couples with the same immediacy as humans.

The most widespread human numeral system employs ten digits - most likely because human count on their hands, and hands have ten fingers, but every integer above 2 can be used as a basis. Different cultures have used nearly every number up to 30, especially with the 20-digits system (used by Celts, Maya, Yoruba and many others). Since computers use the most simple numeral system, the one with only two digits (1 and 0), the astrophysicist Fred Hoyle suggested that humans could have developed digital technology much earlier if they had four, eight or sixteen (powers of two) fingers.

Religion and SpiritualityEdit

Also see: here and following pages

Ritual behaviours (sequences of specific actions with a determinate social effect) are common among the vertebrates, from the variety of dominance and courtship displays to the rudimentary funeral rites of elephants. Every human culture has developed specific rituals for all the main individual events: birth, acceptation into the community, puberty, marriage, death.

At their root, religions are usually hinged on the origin of life: the maternal womb and the soil in which plants grow are the most ancient and common gods (the same womb-earth equivalence would be equally valid for egg-laying sapient: in fact, eggs are a common symbol of life even for humans). In a subsequent phase (probably with the start of agriculture) these female symbols were replaced by the male seed, believed to be the true origin of lifeforce, and its ecological analogue: rain and the Sun, which "fertilise" Earth and make it fertile. The two principles of life, female and male, are inevitably Mother Earth and Father Heaven (though the arrangement is likely to be different in a species with less or more than two sexes). Likely objects of worship include:

  • celestial bodies (star(s), moon(s), planets, rings);
  • natural features (rivers, lakes, mountains, volcanoes);
  • natural events (eclipses, volcanic eruptions, thunderstorms, auroras);
  • living organisms;
  • biological processes (pregnancy or egg incubation, breath, sex, death);
  • mental processes (dreams, hallucinations, reason).

More mature religions can have a more complex theology, but they still deal with the worship of earth and/or heaven, and the rituals are usually connected to biological and astronomical cycles: generations, the menstrual cycle, months and seasons, the springly renewal of life (survived as Resurrection in the christian Easter), etc. Another common tract is the survival of individual consciousness (or other kinds?) to death, sometimes undifferentiated and equal for anyone (the mesopotamic Arallu, the greek Hades, the ancient jewish Sheol), sometimes based on afterlife justice.

The specific conditions in which a people lives directly shape its beliefs. Abrahamic religions (Judaism, Christianity and Islam), born in an arid environment where every need of life must be created by man, see in everything a deliberate divine design, and hope for a future of rest and abundance, as a messianic kingdom on Earth (for jews) or in the afterlife (for christians and muslims). Conversely, dharmic religions (hinduism, jainism, buddhism, sikhism), born in the tropical seasonless fecundity, see existence as an infinite cycle of rebirths, to be broken through asceticism and rejection of material goods.

In most cases, the rituals of connection with deities include a request for favors (luck, protection or forgiveness), which are repaid with a sacrifice, often animal or even human - sometimes just in a symbolical form (such as the christian Eucharist).

Over these basic elements, finally, there is a complex web of traditions, laws and prohibitions, often arbitrary, and communal rituals, mostly to the purpose of reinforcing group identity.

Art and AestheticsEdit

Also see: here and following pages, Perception

Alien artistic and aesthetic value are simply unknowable: even in the same species a culture might prefer expression of conflict and turmoil, another order and armony. The only factor that can be deduced from its biology is the dominant sense: human art is mostly visual or acoustic, or both, while tactile or olfactive art is extremely rare (though light and sound, being waves, have the absolute advantage of being easily broadcasted at distance).

The philosopher Abraham Moles classified artworks on the basis of three criteria: the spatial aspect (adimensional, one-dimensional, two-dimensional or three-dimensional), the temporal aspect (static, if it lack an element of time; kinetic, if it varies with time; dynamic, if it's influenced by the viewer) and the perceptive aspect (visual, acoustic, olfactive, tactile, electric, magnetic, etc. or mixed). For example, a concerto for piano is adimensional, kinetic and acoustic; a statue is three-dimensional, static and visual; a movie is two-dimensional, kinetic and mixed; a dance is three-dimensional, dynamic and mixed.

Stimuli of a sense can be classified by intensity and "tone": visual and acoustic tones (colours and pitch) correspond to the wavelength of light and sound; their analogue in other senses could be olfactive "hues", temperature or electric resistence. Even conserving the same sense its artistic rendition can be very variable: the paintings of a species with a bee-like vision will be rich in blue and violet, and UV parts invisible to human eyes; those of a species with gull-like vision will contain mostly orange and red, and equally invisible infrared parts. Sapient rattlesnakes could "paint" with heated materials that emit infrared light.

Ecolocation and electric senses can pass through differente layers of matter, giving a stratified three-dimensional vision on the interior and exterior of an object. The "portraits" of a species with such a perception could be machines (maybe vibrating laminae with echo chambers) that emit a specific sequence of high-pitched sounds that wouln't be visually similar to the object they represent; likewise, they'd see a human painting as a thin block that doesn't resemble the subject at all. Since Doppler effect is much more noticeable with sound than with light, changing the frequence of the portrait would give the appearance of movement.

Even more unusual to human observers would be the chemical art of a species with smell-based perception; their "paintings" might be porous surfaces apparently bare but permeated in different perfumed substances, and their movies would involve a sequence of scents (each of which would influence the following, unless they're rapidly cleared away).

The most important aesthetical criteria will likely be about the physical aspect (sound, shape, temperature, scent...) of their own conspecifics. They will most probably consider three factors:

  • Marks of good health (such as symmetry, regular body proportions, a complete body covering, etc.);
  • Traits that help survival and procreation (for example strong biological weapons, features linked to sexuality and childbearing, fat storages for desert-dwelling species, dense fur in cold enviroments, etc.);
  • Signals of high social status, if such a thing exist for them: for most of the European history, pale skin and fatness were considered attractive since typical of nobility as opposed to thin and dark-skinned peasants.

It's not uncommon that sexual selection causes the development of traits detrimental to survival, but precisely for this reason considered marks of fitness and therefore attractiveness.

Language and writingEdit


In the broadest sense, a government can be defined as a social system that stores and uses information about the society to mantain order and complexity; for this purpose, it needs comunication with the rest of the society and a way to exercise control, probably through a monopoly on force (police and army). While a species with genetic sentience might not need a form of government to mantain social order, it's probably safe to assume that every sapient species with individual sentience will.

Traits of governmentsEdit

There are many possible ways to classify governments according to their features. This one[6] takes into account seven traits: extension of the leadership, legitimation of the leadership, degree of centralization of the government; economic exchange system; economic basis; individual sociopolitical freedom; size of the civilization.

Leadership size Leadership legitimation Centralization Exchange system Economic basis Political freedom Cultural scale
Pantisocracy Biological Decentralized Gift exchange Laissez faire Libertarian Subplanetary
Democracy Sociocultural Alliance Barter Feudalism Egalitarian Planetary (I)
Republic Socioeconomic Confederation Valuable money Merc., Welf. Authoritarian Stellar (II)
Oligarchy Personal force Federation Symbolic money Corporations Totalitarian Galactic (III)
Autocracy Election Empire Obligation Socialism Universal (IV)
Anarchy Unitary gov. Communism
  • The fraction of the society that takes part in the government can vary from nobody to everybody, through anarchy (rule by none), autocracy (rule by one), oligarchy (rule by few), republic (rule by many, generally defined as a government everyone has the possibility to join), democracy (rule by most) and pantisocracy (rule by all).
  • This fraction needs then a legitimation that gives it the authority to head the society. The many basis used by human cultures have been biological (rule by species or race, e.g. nazism; rule by gender, e.g. patriarchy or matriarchy; rule by age, e.g. gerontocracy; rule by descent, e.g. aristocracy, monarchy, castes), sociocultural (rule by ideology, e.g. fascism; rule by prestige or merit, e.g. meritocracy; rule by constitution, e.g. constitutional monarchy; rule by divine right, e.g. absolute monarchy, theocracy, hierocracy), socioeconomic (rule by wealth, e.g. plutocracy; rule by property, e.g. feudalism, timocracy), based on personal strenght (e.g. despotism, military junta, stratocracy) or election (elective monarchy, democracy).
  • The degree of centralization measures how much authority the central government has over its local branches. A confederation is a loose union of political organs that mostly govern themselves, at most with a common constitution, and a minimal support role from the centre (an alliance is a limited form of confederation with a specific objective); a federation is made up by partially self-governing states or regions that share their power with a central authority; a unitary government has a single focus of authority that concentrates all powers. Empires are typically mostly unitary, but they often have a scundary government for the outer colonies.
  • The exchange system is the way a culture deals with disparity of resources between social units. It can be based on a simple exchange of gifts, or a more complex system of barter, which might comprehend a particularly common resource used as universal currency; this resource can be used as valuable money, but this is likely to be soon replaced by symbolic money, which has no value in itself except when exchanged with other things. At a certain point, money could be replaced by obligation, in which the credit itself is exchanged between units.
  • There are different ways a government can deal with economic transactions between citizens: in a laissez faire economy, it doesn't participate at all, except to uphold laws (with the particular form of piracy, where economy becomes a matter of strength and cunning); with feudalism, the control of citizens is replaced by a hierarchy of contracts where each lord has political power in its fiefdom; mercantilism and welfarism are two mild forms of national control of the economy, one based on regulation of trade through taxes and subsidies, and the other on promotion of the welfare of the citizenry; corporations are groups of individuals that act with the powers and rights of a person; socialism is a system where the government has full control over the means of production, while in communism it controls both the means of production and distribution.
  • The society can grant liberties to individuals in at least four ways: in libertarian societies, each individual has full personal civil, political, economic and communicative liberties; in egalitarian societies, some liberties may be given up for the community's sake, but everyone has to be treated in the same way; in authoritarian societies, political influence is concentrated in the authority; in totalitarian societies, every aspect of the life of each individual is controlled by the government.
  • The scale of the culture is based on the energy consumption (see below).

Combination of TraitsEdit

The political traits outlined above can be combined in any way, but they'll be influenced by pre-existing cultural traits, and by each other. As already said, in the case of genetic sapience a true government would be unnecessary, as the action of each individual would be directed to the well-being of the community: such a society would be anarchic, totalitarian, decentralized and communist by nature. High degrees of centralization should be limited to individually sentient societies.[7]

Communally sentient species are instead likely to be restricted to smaller scales, as the speed of light would severely restrict the communication they need to process information. Such a society should be naturally pantisocratic, as every individual would be aware of the thought processes of everyone else. As with genetic sentience, individual profit wouldn't be relevant, though this wouldn't contradict libertarianism.

As for size (the number of relevant social units that make up the civilization, regardless of the spatial distance between them), a larger size requires obviously a higher cultural scale to sustain the population, and it makes its government more relatively oligarchic, while a small size easily allows democracy and pantisocracy. At the same time, with growing size, high centralization, gift exchange and barter, state-controlled economy and authoritarianism/tolitarianism become less likely, due to the difficulty of controlling a great number of individuals and interactions.

Dispersion is the relative distance between social units. A low-technology civilization might be highly dispersed on an archipelago, or living as nomads in a vast and arid environment, but interstellar or greater civilization should always be dispersed regardless of their advancement (assuming that faster-than-light travel and communication is indeed impossible). While low dispersion would allow any political trait, high dispersion would hinder high centralization, state-controlled economy or symbolic currency, while making all but certain libertarianism, and encouraging autocracy or oligarchy (perhaps with feudal-like economy) on the isolated units.

Another factor is the diversity of the cultural heritage. With a great cultural (or even biological) heterogeneity, it would be more difficult for the authority to impose the same values on all citizens, and for citizens to share political responsabilities: this factor would lead to more oligarchic and autocratic but decentralized governments, a simpler exchange system based on barter, free economy and libertarian ideals.

Laws and CrimesEdit

A civilization will need its own ethics, that is, a system of rules and concepts that define a good conduct in society; laws will be the government's way to enforce ethics on the population. Many human ethical systems have a religious origin, and give authority to their rules by ascribing them to god(s), though areligious ethical systems are common (Buddhism, Taoism, secular humanism, etc.).

It's very likely that an individually sentient social species will evolve a strong empathy to control violence inside the community: therefore, an ethical principle based on identification between self and others (such as the Golden Rule, which appeared several times among different human cultures) will be common. Other rules will favour the society in which they're developed: in times of abundance reciprocal help will be good, while in times of scarcity a more individualistic behaviour might take over. As a universal ethical system, thermodynamic ethics has been proposed: a set of rules that value the capacity of reducing entropy, that is, life and intelligence over inert matter[8].

True laws, differently from simple ethical rules, will need authority from the government and some kind of sanction for lawbreakers, be it physical violence, confinement, money sanctions, expulsion from a group, cleansing rituals, ostracization, etc. The sanctions may be based on different rationales: revenge, expiation (spiritual purification of the sinner), deterrence, isolation (to protect society), rehabilitation or compensation of the victims.

Most likely, murder will be a universal crime, with two caveats: there will be exceptions that make acceptable a killing, such as legitimate defense, death penalty, war, population control through infanticide, killing disabled individuals to save resources (as Inuits did; this should be common in environment with a serious resource scarcity); and it would probably be a crime only when the victims are part of the same community, rather than foreigners, in a dispersed, tribal society. Sexual and economic crimes will be less universal: for example, the concept of private property might not exist in nomadic cultures where individuals cannot accumulate many material goods.

Advanced CivilizationsEdit

Though fossil fuels and radioactive materials are present in a finite supply, and geothermic energy might not be easily accessible, solar irradiation and hydrogen for fusion reactors should always be abundant enough to indefinitely fuel a planetwide civilization, especially if the planet is rich in hydrogen compounds such as water, ammonia or methane. Yet, the consumption of an expanding civilization rises exponentially, and after several centuries or millennia even the quantity of hydrogen in a whole planet might be depleted, and the star(s) will burn out in a few billion years (faster if they're F-class or early G-class).

The human worldwide energy consumption, estimated to be 1.62×1013 watts in 2010, is believed to have increased of 0.3% per year in the pre-industrial period, and of 3% per year after the Industrial Revolution. At this rate, it will be equal to all energy received by Earth from the Sun in roughly 300 years. At this point, a civilization faces both the problem of finding extraplanetary energy and that of the buildup of waste heat, and it will be forced to expand to other worlds.

The Kardashev ScaleEdit

This scale[9], proposed in 1964 by the russian cosmologist Nikolai Kardashev, is used to measure the advancement and expansion of a technological civilization on the basis of the amount of energy it requires for all its activities. Originally, Kardashev assigned to type I the civilizations that consume the rough amount used by mankind at his time (4×1012 W), to type II those who consume all the energy of a Sun-like star (4×1026 W), and to type III those who consume the energy of the whole Milky Way, or similar galaxies (4×1037 W). Today, the Kardashev Scale is defined as a logarithmic scale, where the rank K is K = (log10P)/10, where P is the energy consumed measured in megawatts (millions of watts).

  • Type I (planetary) civilizations consume 1016 W. They harness all the power of their planet, or an equivalent amount - including the energy of earthquakes, wind, oceanic currents, weather, the heat from the nucleus, and all the light received from the main star. Given the current trend, mankind is predicted to become a type I civilization in the 23rd century. However, since every process that involves energy being moved or transformed releases heat, late Type I civilizations might experience overheating: about 1% of the global amount of energy could be enough to make an Earth-like planet uninhabitable[10]. This would happen sooner on worlds with thalassogens with a low heat capacity, such as sulfur or carbon dioxide.
  • Type II (stellar) civilizations consume 1026 W. They use roughly all the power of a medium-sized star such as the Sun: they'd build a Dyson sphere to capture every photon emitted from it: in fact, a star colonized by such a society would be invisible from the outside. This amount of energy should be able to fuel abundant interstellar travel. Assuming a costant growth in energy, mankind would become a type II civilization around the 4th millennium.
  • Type III (galactic) civilizations consume 1036 W. They extend the photon-harvesting of type II civilizations to all the stars of a whole galaxy, which would appear invisible from outside, save for an inevitable heat leakage. A stellar civilization might get to this point in 100 000-a million years.
  • Type IV (universal) civilization consume 1046 W, the power of 250 millions of Milky Way-like galaxies. Such a civilization could engulf entire clusters of galaxies, creating huge void areas in the Universe - like the Boötes void, a region 250 millions light years across, with only a few tens of galaxies visible.
Example Energy output/consumption Kardashev number
Smallest electromechanical operations[11] 9×10-18 W -2.40
Average human cell 10-12 W -1.80
A cricket singing 9×10-4 W -0.90
Average human consumption at rest 1.0×102 W -0.40
Average human power use (2008) 2.4×103 W -0.26
World population of chimpanzees 1.09×107 W 0.10
Average nuclear reactor 8.5×108 W 0.29
Roman Empire at its apex 3.0×109 W 0.35
First stage of the Saturn V rocket 1.9×1011 W 0.53
Mankind in 1900 8.7×1011 W 0.59
Mankind in 1973 1.0×1013 W 0.70
Mankind in 2010 1.62×1013 W 0.72
Heat flow from the Earth's interior 4.4×1013 W 0.76
Photosynthetic biomass production 7.5×1013 W 0.79
Average hurricane 5×1013-2×1014 W 0.77-0.83
Planetary Civilization 1016 W 1.00
Solar energy received by Mars 8.53×1016 W 1.09
Solar energy received by Earth 1.74×1017 W 1.12
Solar energy received by Mercury 6.83×1017 W 1.18
Energy emitted by Proxima Centauri 6.52×1023 W 1.78
Stellar Civilization 1026 W 2.00
Energy emitted by the Sun 3.83×1026 W 2.05
Energy emitted by Sirius 9.7×1027 W 2.20
Energy emitted by Deneb 1.2×1032 W 2.61
Galactic Civilization 1036 W 3.00
Energy emitted by the Milky Way 4×1037 W 3.16
Average quasar 1039-1040 W 3.30-3.40
Average gamma-ray burst 1042 W 3.60
Cosmic Civilization 1046 W 4.00
Total energy of the Visible Universe 2.0×1049 W 4.30

Of course, a civilization could always exploit its energy source in ways that increase the output at the expense of longevity, for example extracting hydrogen from a star to fuel nuclear reactors, rather than waiting for natural fusion. The rough amount of matter and energy available to a civilization of each type, as well as the maximum amount of information they'de be able to process as a whole, can be thus summed up:

Civilization Available mass Avalaible power Maximum information Total energy
1 (Planetary) 1025 kg 1016 W 1037 bit/sK 1026 J/ka
1029 J/Ma
1032 J/Ga
2 (Stellar) 1030 kg 1026 W 1048 bit/sK 1036 J/ka
1039 J/Ma
1042 J/Ga
3 (Galactic) 1041 kg 1036 W 1059 bit/sK 1046 J/ka
1049 J/Ma
1052 J/Ga
4 (Cosmic) 1051 kg 1046 W 1069 bit/sK 1056 J/ka
1059 J/Ma
1062 J/Ga

Note: the information is measured in bit that can be processed per second, per kelvin of temperature; the energy is given as the amount collected in a thousand years (ka), a million years (Ma) or a billion years (Ga).


Also see: here and following pages
Once that a civilization has exceeded the Type 1 threshold, it can attempt projects much greater than a planetary surface would allow. An advanced Planetary Civilization, for example, could try to expand its inhabitable space (without interstellar migration) through terraforming, that is, altering the environmental conditions on other planets and moons.

In one of the earliest examples, Carl Sagan proposed to cool down Venus by seeding its atmosphere with algae that would sequester carbon from the atmosphere, though the high temperature and pressure would release it back again. Other proposals include pumping oxygen and other gases to form a breathable atmosphere on the Moon, and warming Mars up by covering its polar icecaps with a low albedo material, such as carbon dust or vegetation, thus trapping solar heat and melting the ice; its moon Phobos might be moved to alter its seasons; electrolysis could be used to release oxygen from permafrost ice; water could be introduced to Mars by moving there large quantities of ice from Saturn rings. Ecosynthesis or ecopoiesis involves importing plant life on Mars to form, in the course of thousands of years, a self-sufficient biosphere.

Each building project requires transporting matter on astronomical distance or harvesting it from celestial bodies. We already know (see above) the maximum amount of mass and energy that each type of civilization can manage; while Planetary Civilizations could move only objects the size of an asteroid, Stellar Civilizations should be able to move and mine entire planets. The energy needed to move an object can be calculated as E=0.5×mv2, where m is the transported mass and v is the velocity to be imparted, though it tends to infinity as the velocity approaches the speed of light (c). The needed velocity could be imparted vaporizing a relatively small amount of matter in one point on the surface of the object, thus pushing it in the opposite direction.

There are at least three ways to dismantle planets and stars. In centrifugal disruption, the less onerous, rotation is accelerated until the object fractures under its own internal stress; this could be achieved creating on the Equator several jets of matter as those used for transport, or encasing it in a magnetic field and creating a force with another magnetic field in orbit. Jovian planets and stars can be stripped of their hydrogen for nuclear fusion, turning it into denser elements as waste. Finally, planets and stars can simply be destroyed through explosive force.

Given a sufficient amount of matter and energy, it's possible for Stellar or greater civilization to expand their inhabitable space beyond planet surfaces by building new habitats in space.
  • O'Neill Island One is a spherical shell 500 m in diameter, rotating at 110 revolutions per hour so that the equator of the sphere experiences a force pushing toward the inner surface equivalent to Earth's gravity. With sunlight reflected by mirrors located at the poles, it could sustain ten thousand people. Cole Planetoid is a similar structure, built from an asteroid of roughly 1013 kg, melted and consolidated as a hollow cylinder 10 km wide and 20 km long, with an interior layer of air about 3 km thick. These projects are within the reach of a Planetary Civilization.
  • Topopolis is a rotating cylinder with a diameter of 1-2 km, of any length; it can be looped around a star, forming a huge torus with the inhabitable surface of 20 Earths, but with a mass a thousand times smaller. A shell of satellites or smaller habitats such as Cole Planetoids spread as a spherical shell around a star form a Dyson sphere, a simple method for a Type 2 Civilization to collect all the energy output of their sun (it should be possible to build it as a solid, if thin, shell, but it'd have a low stability and a negligible gravity). Larry Niven's Ringworld is a ring with the same diameter as Earth's orbit, with walls 2000 km high (enough to retain an atmosphere without a roof) and a floor a kilometre thick (if built with the mass of an entire solar system); day and night could be simulated by a seond ring with alternate opaque and transparent panels, and seasons by changing its inclination; it would have the surface of three millions Earths. These project should be feasible for Stellar Civilizations.
  • With a radius of 4 AU and the mass of 3000 Suns, the Alderson Disk requires at least a Galactic Civilization to be built. 5000 km thick, its rotation provides a (perpendicular) gravity six times lower than Earth's, but the surface offered on the two sides is four billions times larger, even ignoring the vast area too cold or too hot for Earth-like life. The Megaring is a variation of the Ringworld massive even for a Type 3 Civilization: it's a million km wide, with a diameter of 20 light years. Its rotation at 0.1 c provides a gravity 1000 times lower than Earth's; hundreds of thousands of stars circle the ring at 1 AU of distance, providing light and heat; while weighing only 300 solar masses, it needs a mass of air ten times greater.
  • Beyond this point, a Cosmic Civilization is needed for larger projects: a Megaring with a diameter of 2000 light years, with negligible gravity and air-retaining walls 4 AU high, lightened up by a quasar at its centre; a Megadisk 20 light years wide and only 100 km thick, which needs a whole galactic mass (1041 kg) of air on a ten times heavier frame to keep a pressure of 1 atm, and would have a surface of 1020 Earths; a solid Megasphere 200 light years wide, with 130 000 square light years of surface on each side. With a mass much greater than this (over 1300 galactic masses), a solid structure would risk to collapse into a black hole.

Based on the availability of mass and energy given above, it's possible to build a summary of hypothetical engineering projects on astronomical scale.

Project Needed energy Needed mass Civilization
Venus clouds algae-seeding 1018 J 109 kg 1 (0.001 y)
Lunar atmosphere (1 atm) 1024 J 1018 kg 1 (1000 y)
Mars: Polar albedo change 1021 J 1013 kg 1 (1 y)
Mars: Moving Phobos orbit 1023 J 1016 kg 1 (100 y)
Mars: Permafrost electrolysis 1023 J 1018 kg 1 (100 y)
Mars: Planetary ecosynthesis 1024 - 1025 J 109 - 1013 kg 1 (1000-10 000 y)
Mars: Ice from Saturn rings 1028 J 1018 kg 1 (107 y)
Moving and mining
Transport: Asteroid 1019 - 1021 J 1012 kg 1 (0.01 - 1 y)
Transport: Terrestrial planet 1032 - 1038 J 1025 kg 2 (10 - 105 y)
Transport: Jovian planet 1034 - 1040 J 1027 kg 2 (1000 - 109 y)
Transport: Star 1037 - 1043 J 1030 kg 2 (106 - 1012 y)
Transport: Galaxy 1044 - 1054 J 1036 - 1042 kg 3 (1000 - 1013 y)
Centrifugal disruption: Terrestrial planet 1031 J 1025 kg 2 (1 y)
Centrifugal disruption: Jovian planet 1035 J 1027 kg 2 (10 000 y)
Fusion disruption: Jovian planet 1036 J 1027 kg 2 (105 y)
Fusion disruption: Star 1039 J 1030 kg 2 (108 y)
Explosive disruption: Terrestrial planet 1032 J 1025 kg 2 (10 y)
Explosive disruption: Jovian planet 1036 J 1027 kg 2 (105 y)
Explosive disruption: Star 1041 J 1030 kg 2 (1010 y)
Explosive disruption: Galaxy 1047 - 1054 J 1036 - 1042 kg 3 (106 - 1013 y)
Large scale buildings
O'Neill Island One 1017 J 1010 kg 1 (0.0001 y)
Cole Hollow Planetoid 1022 - 1023 J 1013 - 1014 kg 1 (10-100 y)
Topopolis (toroidal world) 1027 - 1028 J 1022 kg 1 (106 - 107 y)
Dyson sphere (ø 2 AU) 1036 - 1037 J 1027 - 1028 kg 2 (105 - 106 y)
Ringworld (ø 2 AU) 1036 J 1027 kg 2 (105 y)
Alderson Disk (ø 8 AU) 1045 J 1034 kg 3 (10 000 y)
Megaring (ø 20 ly) 1045 - 1046 J 1035 - 1036 kg 3 (104 - 106 y)
Megaring (ø 2000 ly) 1051 J 1043 kg 4 (1 y)
Megadisk (ø 20 ly) 1054 J 1043 kg 4 (1000 y)
Megasphere (ø 200 ly) 1056 J 1045 kg 4 (105 y)

Notes: the energy requirement for transport assumes that the object is trasported at 10 km/s (lower value) and at 1% of the speed of light (higher value); the last column gives the type of the smallest civilization that can manage the necessary energy and the time, in years, that civilization would need to amass all the energy, provided that it commits 1% of all its energy sources to this purpose.


  1. Robert Freitas, Xenology, chapter 15.1. <>
  2. "Efficiency & Cost", Distributed Generation, 2007. <>
  3. Jared Diamond, "What Makes Countries Rich or Poor?", The New York Review of Books 7 June 2012. <>
  4. "The Value Orientations Method: A Tool to Help Understand Cultural Differences", December 2001. <>
  5. Robert Freitas, Xenology, chapter 20.4.1. <>
  6. Based on the one employed in Xenology, chapter 21. <>
  7. Based on Xenology, chapter 22. <>
  8. Entropy Ethics, Hmolpedia. <>
  9. George Dvorsky, "How to Measure the Power of Alien Civilizations Using the Kardashev Scale", io9, 25 February 2013. <>
  10. Robert Freitas, Xenology, chapter 15, "Planetary Cultures". <>
  11. Any operation smaller than this is overwhelmed by random thermal fluctuations.

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