The Question of Appareance

As we have seen, knowledgeable commentators on ufology do not object to the extraterrestrial hypothesis on the basis that there are no extraterrestrials. Some apparently learned commentators do object that any visiting extraterrestrials will not look at all like us, and that the anthropomorphic similarity of the described look at all like us, and that the anthropomorphic similarity of the described "ufonauts" is alone enough to disqualify those reports as fantasy s1Simpson 1964 s2Dobzhansky 1972. But, whereas a precise identity to Homo sapiens in UFO reports would be very difficult to explain in any independent evolution scenario, a similarity of basic patterns of structure may be far more likely than is generally recognized.

Commentators on advanced extraterrestrial life can agree on several foundation stone concepts. This life will be based upon the same primary elemental mix, the same solvent, the same basic chemistry, and polymers of amino acids and nucleic acids, and the energy systems utilizing phosphate molecules. The life forms will develop in relatively similar physical environments, including solar radiation, atmosphere contents, comparative planetary masses, temperature similarities.

Observing the apparently required sequence of evolutionary events, one must add to those similarities multicellularity, oxygen-use, sexual reproduction, large size, mobility, and, if a manipulative tool-user, evolved from a land-dwelling animal form. The large size (required of any intelligent evolved creature) demands several other crucial characteristics. The creature must be a large tube with an input end and an output end, a "head" and "tail." Nutritional intake, processing, absorption, and rejection proceeds most efficiently on a linear assembly line basis. Simple osmosis or other more passive mechanisms cannot deal with a large land-dwelling situation. For the same reason there must be a branching tubal circulatory system powered by a pump to reach all cells. The gas transport system should use the same tubes to avoid redundancy. The large mass will require a skeleton, which must be internal to allow mobility and flexibility. Such an animal will be bilaterally symmetrical along the line of the tube. The head end will concentrate the central nervous system and the major information-gathering senses, especially sight and sound. The brain must be seriously protected by some enclosure, and be directly and proximately attached to the major sensory organs.

These traits are recognized as required or determined by simple logic and physical laws. They are also recognized as being wholly dominant in all large land-dwellers and most large water-dwellers on Earth. This is not in any way an accident peculiar to our planet, but the result of limited sets of possible forms being tested and retested in the fires of universal physics, chemistry, and predator-prey relations. We are beginning to discover these limitations as biologists begin to apply physical principles to biological structures and systems. We are beginning to realize the power of certain structures or packages of chararacteristics as we learn more about evolution and its parallel or convergent production of similar traits. As is now commonly stated in reference to the two dozen or more independently evolved eye structures: some ideas are so important that they must independently reoccur many times. If ETI life forms did not have very similar visual organs situated close to the brain and above the food-intake orifice it would be an astonishing surprise.

The most convincing trend in biology which will indicate the likelihood of structural similarity of advanced life forms everywhere comes from the growing application of physical principles to biology. The field is still largely in infancy but the initial insights are impressive. Limitations on the variety possible in design turn out to be far more restrictive than most biologists suspected. The systems of fluid transport and filtration are based on only 5 and 6 design principles, respectively, no matter in which life form they appear. An interesting specific example of limited design is the "fibrewound cylinder," the commonest skeletal unit on the planet. This structure appears in plants, many lower animal forms, and some higher animal forms such as the swimming mammals. It allows lateral bending while resisting longitudinal compression, a useful combination of flexibility, mobility, and strength. A particular angle for winding the fibre around the cylinder is most efficient in balancing these traits. This exact angle evolved several times, let alone the separate evolution of the structure-at-large s3LaBarbera 1986. Mathematics and physics will apply everywhere. So too will fibre-wound cylinders wound at terrestrially-observed angles.

Even large biological categories, such as skeletons, have limited numbers of designs. A finite definable number of skeletal types has been described and related to earthly forms. Almost every type turns out to exist on Earth, most of them with many representatives s4Reif & Thomas 1986. The message is this: physics, geometry, strength of materials limit the number of structural possibilities. Within these limits a dynamic ecology will inevitably fill each useful structural niche, usually many times over.

We are not pretending that the outcome of evolution was fully determined or predictable, but we want to argue against the supposition that all things are possible. The same design elements show up again and again s5R. D. K. Thomas, Franklin & Marshall University.

A rather amazing case of structural determinism has been presented in the relationship between the capacity of mammalian bones to accept stress (before breaking) and the maximum likely stress those bones will be called upon to withstand in their owner's lifestyle. Investigators looked at small mammals such as rodents, at medium ones such as humans, at big ones such as elephants. All the ratios turned out to be exactly the same. Somehow the trials and errors of survival in nature have converged s6Reif & Thomas 1986. Balancing all the differences of mass, activity, jumping, running, fighting, every type of mammalian bone became designed to achieve the same safety factor: they all can sustain three times the force they are likely to encounter in their lifestyles. This is another apparent example of a powerful order-giving trend governed by basic physical principles, which in this case makes all bony skeletal mammals astonishingly the same. Similar mathematical relationships exist for hydrostatic skeletal structures such as tentacles, tongues, and elephant trunks. Would these same principles apply elsewhere in the galaxy? It is difficult to conceive why not.

With these encouragements in mind let us address a prominent observable feature in advanced life forms which some scientists seem ready to doubt in an alien life form: the number of limbs, two arms, two legs. How really unlikely is it that advanced intelligent life forms evolving elsewhere will have this familiar morphology? A brief examination of our own development of this pattern may offer some grounds for more than a purely intuitive comment. Life here developed in the seas and moved to the land. Such a pattern must be the pattern elsewhere as well. Earthly life in the seas had a long period for advancement before the constitution of the atmosphere allowed movement to the land. Oceanic life was therefore quite advanced before any elaborate land life was possible. Given the time scale for such atmospheric change, this also should be the general pattern elsewhere. Many sorts of things can ultimately crawl up out of the sea to make a living on the land, but only the bony skeletal vertabrates were able to support the size, mobility, and potential for intelligence necessary to be a dominant advanced form. Again, and as we have seen, it is simple physics. It was therefore the fishes from which came the dominant land animals, amphibians, reptiles, and mammals. But what determined the limbs? s7Radinsky 1987

Fish have fins, and it is from the fins that the four-limbed pattern of land-forms developed. Not all fins evolved. Fins along the midline of the animals simply disappeared in the land-forms. Why? They weren't useful anymore. They didn't help move the animal, and steering and stability in a dense fluid medium were no longer relevant. Fins distributed bilaterally in pairs were still useful. Primitive amphibious landlubbers could paddle and flop themselves forward using such fins in the way we might use oars in a rowboat. The more out-of-water time spent by the species, the more effective these fins needed to be as true walking structures. But why "four," and not six as in the insects, or eight as in the octopus, or any other number?

One might claim that the major reason for advanced land animals having four limbs was simply an accident of having evolved from fish having four bilaterally paired fins, the pectoral and the pelvic. But fish were not always this way. The earliest forms had no fins. Later, all sorts of patterns appeared, including types with more that four bilaterally paired. Such experimentation by nature continued until the seas became dominated by the pectoral/pelvic pairs pattern. Accidental? Random chance? Almost no serious evolutionist utilizes such explanations today. This pattern became dominant because four was, on the average, more useful; it had a survival advantage. Can we understand what that advantage was?

Any such understandings, like all scientific queries which probe into the past, cannot be stated with certainty. We can, however, make some reasonable assessments based on our current knowledge. To start, since all advanced land life develops from bony vertebrate mobile ocean forms, and such forms are tubal and strongly "ended" in structure, these developed land forms will be tubal, ended and bilaterally symmetric. The likely numbers of fins, which become primitive and evolved limbs, will be "paired": two, four, six, etc., rather than three, five, seven. For all of our advanced forms, the "answer" has been four. A large animal not yet possessed of a significant intelligence, might benefit on the basis of stability alone from more than two limbs. But the main reason is simply that having only two limbs nearly cripples the individual from doing more than one thing at the same time (e.g., standing while defending oneself). But then should not six or eight be better yet? There are two possible reasons why this may not be true, and as knowledge progresses, we'll probably know exactly why four is not only a useful number but a demanded one.

When an animal is large, every major structure of its body is a major genetic and energy expenditure, and a major site of risk. It is a place which can be hurt, infected, and cause death. Adding major structures to a species' form is a situation, therefore, which is carefully weighed by nature's struggle of survival. Six, eight, or multi-limbed organisms minimize their problems by strategies of dropping limbs or regrowing them, strategies inconceivable for a large advanced animal, given the energy and material commitment. Small creatures such as salamanders are probably at the limit of those which can afford such a luxury. Large land-dwellers need very strong supportive members. The problems of dispensing with strong joints and elaborative circulatory and nervous connections, and then restructuring it all later, make it obvious why such a large animal is "stuck with" the number of limbs it has in good times and in bad. More is, then, not necessarily better.

The main factor may be the nature of the brain. A big animal is, in a sense, in more than one place at the same time. Its brain must be able to independently and effectively control each of its limbs so as to avoid the most trouble and accomplish the most gain. The brain seems to be limited as to just how much of this it can do. Perhaps because of the stree of monitoring and station-keeping labor it does keeping track of bones, muscles, sense perceptions, and spatial relations in the limbs, or perhaps because of something even more fundamental about brain structure, the brain seems not to be able to properly focus upon 6 or 7 things at a time. Four things, four limbs, seem easily manageable. Five appendages as with prehensile tails or elephant trunks, seem well-managed also. But six? At this point the brain seems to fail. The six-legged world of insects operates on a non-independent 3-up/3-down "tripod" walking pattern, most of the time. Very little independent control is possible for the minute brains of insects, and so the complex task of walking is simplified by a six-limbed robotic system with a stable tripod always on the ground. Instead of six, we might better consider their brain's task a task of controlling two sets of three during this apparently complex activity.

The octopus is quite intelligent and seems to do a good job controlling its eight limbs, thus contradicting our theory. But despite its abilities as one of the Earth's best problem-solvers, the burden of controlling eight limbs severely limits what it can do. Tentacle movement is extremely complex and most of it must always be left to unconscious robotic control rather than focused intentionality. So limiting is this burden, that despite its high intelligence no octopus can learn a maze s8Reif & Thomas 1986. The explanation for this brain-dependent preference for lower numbers of limbs is not clear, but it seems to be clearly true, and points to why we have four limbs and not six or more. Does this mysterious "mathematics" of our earthly brains apply only to our world? Maybe, but considering that the preference has held so strongly across time and types of species on Earth, one wonders if something more powerful and universal may be going on.

The point of the foregoing is not to prove anything but to show that, at the least, the facile dismissal of morphologically similar aliens needs a lot more work than authoritarian guesswork. A reasonable case can be made that common macroscopic designs happened here and elsewhere on the basic of simple physics, geometry, strength of materials, and whatever yet unknown processes limit the controlling abilities of central nervous systems. Further arguments might be made for four or five digits on hands and feet, the arrangement of facial features, basic advanced reproduction designs, certain patterns of sensory intake and brain processing. But there are also many areas allowing much room for variation within these larger structural designs: mass, size, relative dimensions of structures, colors, textures, secondary sex characteristics, aging and immune system patterns, consciousness cycles, etc. Exact duplication of an Earth-human by an independently evolved ETI is indeed inconceivable by any biologist. Such a UFO report would cry out for a non-independent relationship between the reported "alien" and the reporter. The first place a researcher would look for such a relationship would be in the imagination of the reporter. But a report of a morphologically similar but non-identical alien seems a totally different matter. It is intriguing in fact to note, that on the facts and reasoning discussed above, these reports tend to agree with those things deemed likely to be universal, while differing in those things we know may differ s9Bower 1969 s10Webb 1976. Such an "inspired" dichotomy might well be seen as a positive aspect of the reports than a reason to dismiss them.

If we ever succeed in communicating with conceptualizing beings in outer space, they won't be spheres, pyramids, cubes, or pancakes. In all probability they will look an awful lot like us s11Robert Bieri, Antioch College < Ridpath 1975.