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The Physical Appearance of Intelligent Aliens

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 P.O. BOX 182
 TUCSON, AZ 85702-0182
 Questions, comments, bouquets and/or brickbats
 should be sent to the above address.
 SOURCE: Journal of the British Interplanetary Society
         Vol 32, pp.99-102,1978
         Bearsted, Nr. Maidstone, Kent, England
 There can be little doubt that one of the most important factors that will
 determine the manner in which our society reacts should contact ever be
 established with intelligent extraterrestrial (ET) life forms will be the
 physical appearance,or morphology, of the alien. All the prejudices, the
 fears, the mistrust and the bigotry that exists amongst the races that make up
 mankind will be focusswed into this reaction. Thus, speculating on the
 morphology of an intelligent alien is important for the future of space
 exploration. Serious efforts are now being made around the world in the field
 known as Search for Extraterrestrial Intelligence (SETI) and the manner in
 which our society reacts to contact will depend to a great extent on the
 appearance of the alien. Anticipation of the possibilities now may reveal
 whether a shock for the world is likely. It is also useful to consider alien
 morphology in terms of gaugin g how lok ely the chances of intelligent aliens
 evolving really are.
 The problem of trying to anticipate the physical appearance of the ET is at
 first sight ludicrously impossible. To start with, we don't even know if
 intelligent ETs exist, let alone what their planet of origin is like or what
 their morphology may be.
 Our task is therefore limited to using what knowledge we have of the evolution
 of intelligent life on Earth, considering possible extraterrestrial planetary
 environments and making a series of reasonable assumptions. A combination of
 biology, zoology, and anthropology is required as well as the newer science of
 exobiology. Most important, the overriding thought when considering the
 subject should be "how would this imagined alien become intelligent?"
 Conveniently, disagreement over the likely appearance of intelligent ETs
 divides itself into two opposing camps. On one side are those who take a
 rather anthropormorphic view of the ET and believe that it would basically be
 humanoid in shape with two ,arms, two legs, a head at the top of the body and
 the main 
 sense organs located on the head. Opposing this view are those exobiologists
 who believe that the intelligent ET is bound to appear exotic because the
 creature would inevitably have taken a totally different evolutionary path
 from man and would have arisen in a very un-earthlike planetary environment.
 This article will show, however, that the case put forward by the non-humanoid
 ET protagonists will not stand up to the example of the evolution of
 intelligent life on Earth, nor the necessities of morphology that a creature
 requires to become intelligent. It is therefore suggested here that any
 intelligent life across the galaxy will have evolved into a basically humanoid
 A possibility often suggested by more radical exobiologists is that
 extraterrestrial life might depend on a chemistry that does not require the
 carbon atom. Bracewell [1] has proposed that life could make use of the
 chemistry of the silicon atom rather than the carbon atom. Silicon based
 organisms would, for example, breathe out silicon dioxide (sand) instead of
 carbon dioxide. The rock eating creature has often been suggested as a product
 of this biological system. [An example of this can be seen in the ST AR TREK
 episode about the horta.  AB]
 The problem is that silicon polymers of the protein type are unlikely to from
 the compounds essential for for chemical evolution. Bieri [2] points out that
 the energy requirements for duplicating a living system are fulfilled only by
 carbon and the hight energy phosphate bond.
 It is very difficult to envisage any life other than that based on the carbon
 compounds forming in water. Unfortunately this limits the planetary
 considerations necessary for the evolution of larger sized organisms somewhat
 severely -- in fact it restricts planets that may have intelligent to those
 with broadly Earth-like surface temperatures and pressures. (It also restricts
 the type of star that may shine on life producing planets -- the DNA molecule
 is sensitive to high levels of radiation, particularly  the ultraviolet.
 What of possible creatures that could get by without requiring the
 availability of an Earth-like oxygen rich atmosphere? The conjectured
 'balloon' creatures floating in the gas belts of Jupiter and using, instead of
 oxygen, a metabolism of hydrogen -- could they ever become intelligent ETs?
 And what is wrong with with Fred Hoyle's "Black Cloud," an intelligent gas
 cloud thousands of kilometres across? The answer lies in our prime question,
 "how could this creature become intelliegent?" Intelligence, it is argued
 later, will probably only arise from astimulating predatory existence in a
 harsh but survivable physical environment.
 Conceding defeat to the necessity for life to be based on carbon in a water
 medium, the exotic morphology ET supporters suggest that there are enormous
 variations open to chance evolution even under Earth-like conditions. Slight
 differences in surface pressure, temperature, gravity or solar radiation, they
 argue, will produce widely divergent evolutionary trends [3]. Steen[4]
 suggests that intelligent ETs might be insect like, bird like, fish like or
 even plant like. They may be spherical in shape, glutinou s, jelly-like
 creatures, such as as "Quatermass" might meet, or possibly even a planet sized
 oceanic intelligence such as that in Stanislaw Lem's novel "Solaris."
 For less bizarre (but still very exotic) alien creatures proposed for
 extraterrestrial life bearing planets, the exhibits on display at the National
 Air and Space Museum's "Life in the Universe" section in Washington, DC
 some good examples of exotic aliens [5]. Biologist Bonnie Dalzell has designed
 for a dry Earth-like world the "hexalope," a six legged antelope. For a high
 gravity planet, we are presented with the "bandersnatch," a monstrous
 herbivore with eight legs, a large mouth in its chest, two eyes on stalks and
 ears along the side of its body -- the creature weighs 30,000 lbs. on its 3-G
 world! The intelligent ET that Dalzell presents us with is a six legged toad
 like creature.
 Life on Earth shows us just how strange creatures can become in the chain of
 evolution. The giraffe is a good example of this. But it is highly unlikely
 that these creatures could ever become intelligent.
 The problem ignored by exotic ET protagonists is that speculation on the
 morphology of the ET must take account of the lessons taught us by
 evolutionary development on Earth.
 (The argument for humanoid ETs given here is based on the works of Robert
 Bieri [2], N.J. Berrill [6] and Robert Puccetti [7])
 In the early period of the development of life on Earth, organic matter based
 on carbon compounds began in a water medium before the invasion of the land.
 The early sea bound creatures developed a critical characteristic that would
 decide the future form of land dwellers -- that of bilateral symmetry in the
 shape of the body. This shape reduced water resistance and turbulence to a
 minimum and became the characteristic of all the higher creatures of the sea.
 It can be seen that adoption of a predatory way of marine life has has
 developed has developed bilaterally symmetrical creatures as diverse as the
 squid, the penguin, the seal, the otter and the large fish. Radially symmetric
 ocean dwelling creatures all adopt a relatively stationary way of lif, jelly
 fish, sea anenomae etc., having a loss of sensitivity and degeneration of the
 nervous system when compared to the more active predators.
 Bieri points out that predatory animals with complex nervous systems and
 bilateral symmetry possess the largest and most important sensing and grasping
 organs close to the mouth. Also, digestion and excretion is most convenient
 with an anterior mouth and posterior anus for an active hunting animal. In
 order to reduce time for for nerve impulses to travel from the sensing organs,
 the brain is at the head.
 Conceptualisation, it would seem, can arise only in a land animal. Birds
 cannot possess brains large enough for this due to the fact that they must be
 light in weight and have hollow bones to fly. A large intelligent brain
 requires a considerable amount of blood and therefore a heavy cardiovascular
 system -- both these factors would lead to an impossible power to weight ratio
 for an intelligent airborne creature. It is also difficult to imagine an
 intelligent ET evolving from gliding winged creatures such  as the the flying
 squirrel (which glides from trees with the use of membranes under its front
 legs) -- it is too small to evolve intelligence. It is doubtful that even a
 gliding creature as large as the extinct Pterodactyl could ever develop a
 large enough brain.
 The question of intelligence arising in sea animals is somewhat more complex
 due to the fact that the whale family happens to possess large brain capacity,
 very advanced system of communication and displays remarkable feats of
 intelligence. However, conceptualisation, as Puccetti attempts to define it,
 seems to arise in conjunction with a social existence, speech and the use of
 tools. The development of tool usage undersea is extremely difficult due to
 the density and viscosity of water. Predatory sea animals rely on their
 natural hunting equipment -- teeth, streamlining, speed, etc. -- rather than
 weapons and tools. Only semi-land creatures, such as beavers a nd otters (both
 mammals) possess any sort of manipulating appending and these they use on the
 How the whale family came to develop such a large cerebral capacity tends to
 cast some doubt on the whole question of conceptualisation development. Here
 it is assumed that whales are clever, but do not conceptualise on their
 An encounter, therefore, with a race of intelligent aliens who are either
 aquatic, reptilian or are creatures capable of flight and who developed
 conceptualisation characteristics with a high level of technology, seems
 highly unlikely. Our intelligent ETs would have to be land dwellers.
 It should be emphasized that it seems most likely that all intelligent
 conceptualising creatures in the galaxy will have their own origins in
 predatory animals. Man's origins appear to stem from herbivore apes that,
 faced with climatic and vegetation changes, left the trees, became omniverous
 and adapted to running on the savannah, hunting other animals in groups and
 using their ability to grasp and manipulate to develop weapons, tools and
 eventually a basic technology. It is difficult to imagine a animal b othering
 to use weapons and tools, firstly if it was a fully adapted herbivore and
 secondly if it was already a competent predator, such as the lion or tiger.
 Arthur C. Clarke describes this critical paththat the early hunting apes had
 to take extremely well in 2001: A SPACE ODYSSEY (although of course he did not
 let his apes develop their technology purely on their own initiative.)
 Man has remained the only creature with a technology on this planet because of
 his predatory hunting nature, despite the basic ingenuity of creatures such as
 the ant with its ingenoius city like hills, chimpanzees which can fish out
 termites with sticks, and birds that can break shells with heavy stones and
 the sea otter that can break open shells by floating on its back and beating
 them  against stones on its chest. These creatures have stretched their
 manipulative abilities to the limits.
 The development of legs, arms and grasping appendages is critical to our
 conceptual ET's road to intelligence. A primitive technology will require the
 ability to hold and manipulate, with some degree of sensitivity, basic tools
 and weapons such as clubs, spears, knives and twine. The intelligent ET must
 have this manipulative capability combined with speed of movement, otherwise
 it will remain in its comfortable environment (as did the dolphin) and we
 would certainly never meet it stepping out of a star shi p.
 As a method of movement, sliding, wriggling and rolling are all much too slow
 for the land predator. As Puccetti points out, walking is the only viable
 means of moving at high speeds and for long distances. The wheel was never
 used as a means of locomotion by nature except in some tiny bacteria. Although
 the reciprocating knee joint in the human leg can put up with large shock
 loads and the shoulder aND hip joints can rotate through a considerable arc,
 it is difficult to imagine an organic bearing that coul d rotate through 360
 Insect like appendages are unlikely. Insects possess legs that are basically
 hollow cylinders with muscles and tendons inside the skeletal tube. The
 problem with this arrangement is that if the creature grows in size the tube
 will constrain the inner muscle size -- hence the Tarantula being the largest
 land insect left since prehistoric times. Hard levers and struts surrounded by
 muscles and tendons, as in land walking vertebrates, is a much more likely
 arrangement in the predator land dwelling alien.
 The question of the number of legs is one of the most contentious when
 discussed by those speculating on the morphology of the intelligent ET. The
 four legs that we have are the product of genetic inheritance from our
 earliest mammal ancestors; but this inheritance allowed us great speed of
 movement and thus playeda major factor in the development of intelligence. One
 leg is out of the question -- the creature could never get up if it ever fell
 over. Odd numbers are unlikely because of balance problems. Mor e than four
 can only be found in insects. Galloping after prey with six legs is too
 complex for land predators (and herbivores, as we have established, are
 unlikely to become intelligent). Each leg has to swing through a wide arc for
 speed and with more than four this becomes very difficult.
 Monkeys and apes can use their two legs for manipulation but have to run on
 both arms and legs together. Indeed the ape cannot use weapons to hunt whilst
 running on all fours. It is difficult to imagine the development of an
 intelligent hunting animal animal such as man running on two sensitive
 grasping appendages. Thus we have the evolutionary step of the conversion of
 one pair of legs to manipulating, pushing and pulling devices and the other
 pair to movement. In this way the creature optimises between hi gh speed
 movement and delicate manipulation.
 So far we have formulated the picture of an intelligent ET with a body much
 like our own. Its sensory organs, however, show characteristics that are
 somewhat different, though not greatly.
 Sense organs would largely depend on the characteristics of the aliens
 planetary environment and the illumination provided by the local sun.
 More than two eyes is rare in land creatures -- the spider possesses multiple
  eyes, but they are of doubtful sensitivity, and would confuse a large hunting
  creature. Stereoscopic vision near to the brain and high on the body is the
  most suitable. Binaural hearing would seem the most logical. This is required
  for location bearing -- and thus the ET requires just two ears. Again these
  would be on the head. Only one mouth is needed with the smell sensor close to
  it and taste sensors inside it. The smell sensor can be used for breathing,
  whilst the mouth is occupied with eating and drinking.
 Additional sensory devices such as bat like acoustic ranging systems or infra
 red sensors similar to those possessed by the rattlesnake, are possible. But
 as Bieri points out, the imply a corresponding reduction of vision in the
 normal sun illuminated spectrum. As we have established above that carbon life
 probably only develops on planets with suns much like our own we can assume
 that the visual spectrum would be similar to that on Earth for the alien ET.
 Although, therefore, the sensors of the ET are similar to our own, the
 placement on the head and their form might be quite different. Odd shaped
 heads are likely, different ear shapes and sizes most probable and eye size
 and colour would be different.
 The argument presented above gives backing to the anthropormorphic view of the
 intelligent ET -- that is that the creature would be basically humanoid. But
 this only a starting point. What would the intelligent ET look like in detail?
 This question is, of course, even more difficult to contemplate than
 speculating on the ET's likely basic form. However, here are a number of
 possible variables to consider:
 1. SIZE AND BUILD -- The height and build of the alien has often been
 suggested as being related to the gravity on the creature's palnet of origin.
 A planet slightly larger than Earth, witha subsequently higher gravity would
 result in the alien being squatter, with heavy bones and a powerful physique
 -- in other words, something like a gorilla. On the other hand, a lower
 gravity planet would result in taller, more spindly aliens. This argument is a
 little simplistic in its conclusion and does not explain th e wide range in
 the sizes of Earth creatures -- for example, why is there such a large
 variation in the size and build of the apes, all of which are fairly clever
 It seems probable that one can draw parameters about the ET's size, the likely
 range being between the smallest of the human races (the pygmy) at about  4
 1/2 feet tall and the upper limit being around 7 1/2 feet tall. If the alien
 is very much heavier than man, he would have problems with running for long
 distances in pursuit of prey in his early development as a land predator and
 would require a very large supply of readily available food to maintain
 One interesting point about man is that we appear to be getting taller due to
 our evolution, our bodies are losing their broader muscles and our heads
 changing shape. It is more than likely that the humanoid intelligent alien
 also experiences this form of slow morphological evolution due to changes in
 dietary nutrition and life style. There is, of course, no guarantee tha the
 alien will meet man as we appear now. An intelligent alien basing his
 conception of what man looks like from previously discovered sp acecraft
 message devices (such as those carried by Pioneers 10 and 11), or picked up TV
 images in, say, 50,000 years time, may be in for a surprise when he meets a
 hairless, chinless, towering egghead from Earth!
 Equally interesting is the question of the differences between the male and
 the female of the intelligent aliens' species. Would the two be quite
 different morphologically as in the case of homo sapiens, or would the two be
 virtually indistinguishable as with some creatures on Earth?
 2. SKIN COLOUR -- The wide variation in skin colour and tone with creatures on
 the Earth is enough to indicate the extreme range that couldoccur with the
 intelligent ET. Indeed, why would the ET have a smooth skin? It is possible
 that fur may cover the alien having been left behind after an evolution
 stemming from a bear like creature, for example. (indeed, it is interesting to
 wonder whether whiskers, or some sort of delicate sensory feelers may remain
 with an intelligent creature after it has begun to rel y on its hands).
 3. FACIAL ARRANGEMENT -- This, as already stated, is mainly constrained by the
 smell and taste sensors being close to the mouth and by the need for stereo
 vision and binaural hearing. Beyond this the facial arrangement possibilities
 would be reasonably wide.
 4. NUMBER OF FINGERS/TOES -- Again, variations could be wide although beyond
 ten fingers or toes on each hand or leg would seem excessive and difficult for
 the brain to coordinate. Less than four fingers on the hand would make basic
 technology difficult to manipulate.
 5. INTERNAL CHARACTERISTICS -- The internal digestive, cardiovascular and
 pulmonary systems inside the intelligent ET would most likely be quite
 different and it is not possible to list all the variations within the
 confines of this article.
 Our immediate impressions of the intelligent ET will be critical to how
 society later reacts to the contact. The theme of this article is that,
 because of the evolutionary demands to become intelligent and the probable
 similarity between Earth and the alien planet, the intelligent ET will be
 basically humanoid in form. Therefore, our reaction will most likely not be
 too extreme.
 Various questions, however, remain. For example, how far will the ET have
 evolved beyond the humanoid morphology?
 It is unlikely that prosthetics will change the basic form of the ET. In
 general, artificial limbs (and bionics) are intended to resemble those
 currently possessed. The aliens' view of good looks will be determined by the
 most perfect and healthy of its species. Consequently any artificial aids will
 be designed to blend with the pure form of the alien -- contact lenses
 replacing glasses is a good example of this.
 It is difficult to imagine the advanced alien ever giving up its basic body
 appearance. Some writers have suggested that semi-immortality might be
 achieved by removing the brain from the failing body and installing it in a
 machine, thus creating the cyborg. If this is ever done it is likely that man
 would want the new machine bodyto resemble the original organic body shape. An
 even more radical idea is that once the alien has developed very high levels
 of knowledge and consciousness, the mind may even be li berated from the body.
 If this occurred we might never discover its original appearance.
 A final question is to what degree will alien clothing and cosmetics mask the
 basic morphology? Fashions can enhance and emphasise body shapes in certain
 cases with our own current civilization -- possibly the same will occur in the
 intelligent ET's society. Hair styling, however, is an example of how
 sometimes fashion can seriously alter the shape of the body. Also, any
 spacesuit or breathing apparatus might appear unusual.
 Unfortunately, only through the discovery of artifacts or through contact
 itself will we ever learn what the actual morphology of the alien may be.
 Indeed, the chances are that the first close encounter with an alien
 civilization will be via the radio telescope. Video pictures will in this
 situation have to suffice for many years in the place of face to face contact.
 It is the conclusion of this paper that these images of the intelligent ET
 will not shock us; they may surprise and intrigue us, but it is unlikely that
 mankind will find the alien fearful in physical appearance.
 Hopefully, the ET will feel the same way about us.
 1. R.N. Bracewell, "Life in the galaxy," reprinted in INTERSTELLAR
 COMMUNICATION, ed. A. Cameron (Benjamin, NY 1963).
 2. Robert Bieri, "Humanoids on other planets?" AMERICAN SCIENTIST, LII
 December, 1964
 3. P.M. Molton, "Is anyone out there?" SPACEFLIGHT, 15,p.250, July, 1973
 4. S.W.P. Steen in the review of Freudenthals "Lincos" language, BRITISH
 5. D. Dooling, "Speculating on man's neighbours," SPACEFLIGHT, 17, p232,
 (Juen, 1975)
 6. N.J. Berrill, "Worlds without end," Chapters 9 and 10
 7. Roland Puccetti, "Persons: a study of possible moral agents in the
 universe," Macmillan, 1968

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