4. THE ANTHROPORMORPHIC VIEW
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 , N.J. Berrill  and Robert Puccetti )
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.
5. CONCEPTUALISM AND INTELLIGENCE
Conceptualization, 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, a very advanced system of communication and displays remarkable feats of intelligence. However, conceptualization, 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 and otters (both mammals) possess any sort of manipulating appending and these they use on the surface.
How the whale family came to develop such a large cerebral capacity tends to cast some doubt on the whole question of conceptualization development. Here it is assumed that whales are clever, but do not conceptualize on their existence.
An encounter, therefore, with a race of intelligent aliens who are either aquatic, reptilian or are creatures capable of flight and who developed conceptualization characteristics with a high level of technology, seems highly unlikely. Our intelligent ETs would have to be land dwellers.
6. THE PREDATORY SUPREMACY
It should be emphasized that it seems most likely that all intelligent conceptualizing 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 omnivorous and adapted to running on the savanna, 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 bothering 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 path that 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 ingenious 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.
7. MOVING AROUND
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 ship.
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 degrees.
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 played a 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. More 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 optimizes between high speed movement and delicate manipulation.